MEMS PRESSURE SENSOR AND METHOD FOR FORMING THE SAME

Provided are a MEMS pressure sensor and a method for forming the same. The method includes: preparing a first substrate, where the first substrate includes a first surface and a second surface opposite to the first surface; preparing a second substrate, where the second substrate includes a third surface and a fourth surface opposite to the third surface; bonding the first surface of the first substrate and the third surface of the second substrate with each other and forming a cavity between the first substrate and the pressure sensing region of the second substrate; removing the second base to form a fifth surface opposite to the third surface of the second substrate; and forming a first conductive plug passing through the second substrate from the side of the fifth surface of the second substrate to the at least one conductive layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority to Chinese Patent Application No. 201510084520.X, titled “MEMS PRESSURE SENSOR AND METHOD FOR FORMING THE SAME”, filed with the Chinese Patent Office on Feb. 16, 2015, which is hereby incorporated by reference in its entirety.

FIELD

The present disclosure relates to the technical field of semiconductor fabrication, and in particular to a Micro-Electro Mechanical System (abbreviated to MEMS) pressure sensor and a method for forming the MEMS pressure sensor.

BACKGROUND

A MEMS is a device which acquires and processes information and performs operations. A sensor in the MEMS can receive external information such as pressure, location, speed, acceleration, magnetic field, temperature or humidity, and convert the obtained external information into electrical signals to be processed in the system. An example of a MEMS device may include a temperature sensor, a pressure sensor, a humidity sensor and the like.

The cost performance of a MEMS pressure sensor can be greatly improved by reduced size, increased precision and utilization of a process that is compatible with a fabrication process of an integrated circuit chip. Currently, MEMS pressure sensors include a piezoresistive type pressure sensor and a capacitive type pressure sensor.

The capacitive type pressure sensor has a high measurement accuracy and a low power consumption. A conventional capacitive type pressure sensor includes a substrate, a first electrode layer arranged on a surface of the substrate, and a second electrode layer arranged on the surface of the substrate and on a surface of the first electrode layer. A cavity is formed between the first electrode layer and the second electrode layer, and the first electrode layer and the second electrode layer are electrically isolated from one another with the cavity.

A capacitive structure is formed with the first electrode layer, the second electrode layer and the cavity. The second electrode layer may be deformed under a pressure, which results in a change of a distance between the first electrode layer and second electrode layer and a change of a capacitance value of the capacitive structure. Since the pressure on the second electrode layer corresponds to the capacitance value of the capacitive structure, the pressure on the second electrode layer can be converted into an electrical signal output by the capacitive structure.

In addition, the electrical signal is transmitted between a pressure sensor chip and a signal processing circuit, so that the electrical signal output by the pressure sensor chip is processed. The pressure sensor chip and the signal processing circuit chip are packaged in a system to form a MEMS capacitive type pressure sensor.

In the existing methods for fabricating a MEMS pressure sensor, processes for fabricating the pressure sensor chip and the signal processing circuit are different, and it is difficult to achieve a monolithic integration. Moreover, in a case that an integrated circuit and a pressure sensor are fabricated on a single substrate, the existence of the pressure sensor creates difficulty in making, changing and improving the integrated circuit, and the integrated circuit on the same substrate makes it difficult to fabricate a small pressure sensor. Therefore, a process for fabricating an integrated circuit and a pressure sensor on a single chip is complicated and a device formed by the current process has a large size, thereby increasing its fabrication cost.

In a case that the pressure sensor and the circuit are integrated on a single substrate, if the pressure sensor is fabricated before the circuit is fabricated, a process for fabricating the pressure sensor often affects the substrate and causes a difficulty in fabricating the integrated circuit, thereby reducing production yield; alternatively, if the integrated circuit is fabricated before the pressure sensor is fabricated, the integrated circuit may limit greatly the choice of materials of the pressure sensor and the temperature in a process for fabricating the pressure sensor, thereby decreasing the performance of the pressure sensor.

Hence, there is an urgent need for a method and a structure for effectively integrating a pressure sensor and an integrated circuit.

SUMMARY

The present disclosure provides a MEMS pressure sensor and a method for fabricating the MEMS pressure sensor. In the method for fabricating the MEMS pressure sensor, the MEMS pressure sensor structure and the circuit fabrication processes are independent from one another, selection of materials is more flexible, production yield is high and a subsequent integrating process is simple, thereby improving the performance and reliability of the formed integrated pressure sensor, and reducing the size and process cost.

In order to address the existing issue, the present disclosure provides a method for forming a MEMS pressure sensor. The method includes: preparing a first substrate, where the first substrate includes a first surface and a second surface opposite to the first surface, and the first substrate includes at least one conductive layer arranged on the side of the first surface of the first substrate; preparing a second substrate, where the second substrate includes a third surface and a fourth surface opposite to the third surface, the second substrate includes a second base and a pressure-sensing electrode arranged on or above the second base, the second substrate includes a pressure sensing region in which the pressure-sensing electrode is arranged, and the pressure-sensing electrode is arranged on the side of the third surface of the second substrate; bonding the first surface of the first substrate and the third surface of the second substrate with each other; forming a cavity between the first substrate and the pressure sensing region of the second substrate; removing the second base to form a fifth surface opposite to the third surface of the second substrate; and forming a first conductive plug passing through the second substrate from the side of the fifth surface of the second substrate to the at least one conductive layer, where the first conductive plug is used to electrically connect the conductive layer to the pressure-sensing electrode.

Optionally, the second substrate may further include a fixed electrode corresponding to the pressure-sensing electrode and the cavity is formed between the pressure-sensing electrode and the fixed electrode.

Optionally, the first substrate may further include a fixed electrode arranged on the side of the first surface of the first substrate; when the first surface of the first substrate and the third surface of the second substrate are bonded with each other, the fixed electrode corresponds to the pressure-sensing electrode and the cavity is formed between the pressure-sensing electrode and the fixed electrode.

Optionally, the forming the cavity may include: before the first surface of the first substrate and the third surface of the second substrate are bonded with each other, forming a first opening on the side of the third surface of the second substrate or on the side of the first surface of the first substrate, or, forming the first opening on both the side of the first surface of the first substrate and the side of the third surface of the second substrate, with a location of the first opening corresponding to a location of the pressure sensing region.

Optionally, the first substrate may further include a circuit.

Optionally, the preparing the second substrate may include: preparing a semiconductor-on-insulator substrate, where the semiconductor-on-insulator substrate includes a base, an insulating layer arranged on a surface of the base and a semiconductor layer arranged on a surface of the insulating layer; and forming a pressure-sensing electrode in the semiconductor layer, with the base being the second base.

Optionally, the second substrate may further include a second coupling layer arranged on the side of the third surface; or, the first substrate may include a first coupling layer arranged on the side of the first surface; or, the second substrate may further include a second coupling layer arranged on the side of the third surface and the first substrate may include a first coupling layer arranged on the side of the first surface.

Optionally, at least one of the first coupling layer and the second coupling layer may be comprised of an insulating material.

Optionally, the first surface of the first substrate and the third surface of the second substrate may be bonded with each other by an adhesive bonding process, and the first coupling layer or the second coupling layer may be an adhesive bonding layer which is comprised of an insulating material, a semiconductor material, a metal material or an organic material.

Optionally, the first surface of the first substrate and the third surface of the second substrate may be bonded with each other by a direct-bonding process.

Optionally, the first substrate may include a self-test electrode, and a location of the self-test electrode may correspond to a location of the pressure sensing region after the first surface of the first substrate and the third surface of the second substrate are bonded with each other.

Optionally, the second substrate may further include a reference unit region, a cavity may be formed between the first substrate and the reference unit region of the second substrate when the first surface of the first substrate and the third surface of the second substrate are bonded with each other, and a deformation on a portion of the second substrate corresponding to the reference unit region may be less than a deformation on a portion of the second substrate corresponding to the pressure sensing region under a same external pressure.

Optionally, the method may further include: forming a second opening passing through the first substrate, where a location of the second opening corresponds to a location of the pressure sensing region of the second substrate after the first surface of the first substrate and the third surface of the second substrate are bonded with each other.

Optionally, the method may further include: forming a fourth conductive plug passing through the first substrate from the side of the second surface of the first substrate to the at least one conductive layer.

Accordingly, the present disclosure further provides a method for forming a MEMS pressure sensor. The method includes: preparing a first substrate, where the first substrate includes a first surface and a second surface opposite to the first surface, and the first substrate includes at least one conductive layer arranged on the side of the first surface of the first substrate; preparing a second substrate, where the second substrate includes a third surface and a fourth surface opposite to the third surface, the second substrate includes a second base and a pressure-sensing electrode arranged on or above or in the second base, the second substrate includes a pressure sensing region in which the pressure-sensing electrode is arranged, and the pressure-sensing electrode is arranged on the side of the third surface of the second substrate; bonding the first surface of the first substrate and the third surface of the second substrate with each other; forming a cavity between the first substrate and the pressure sensing region of the second substrate; thinning the second substrate from the fourth surface by partially removing the second base, to form a fifth surface opposite to the third surface of the second substrate; and forming a first conductive plug passing through the second substrate from the side of the fifth surface of the second substrate to the at least one conductive layer, where the first conductive plug is used to electrically connect the conductive layer to the pressure-sensing electrode.

Optionally, the second substrate may further include a fixed electrode corresponding to the pressure-sensing electrode and the cavity may be formed between the pressure-sensing electrode and the fixed electrode.

Optionally, the first substrate may further include a fixed electrode arranged on the side of the first surface of the first substrate; when the first surface of the first substrate and the third surface of the second substrate are bonded with each other, the fixed electrode may correspond to the pressure-sensing electrode and the cavity may be formed between the pressure-sensing electrode and the fixed electrode.

Optionally, the forming the cavity may include: before the first surface of the first substrate and the third surface of the second substrate are bonded with each other, forming a first opening on the side of the third surface of the second substrate or on the side of the first surface of the first substrate, or, forming the first opening on both the side of the first surface of the first substrate and the side of the third surface of the second substrate e, with a location of the first opening corresponding to a location of the pressure sensing region.

Optionally, the first substrate may further include a circuit.

Optionally, a third opening may be formed in the second substrate after the second substrate is thinned from the fourth surface, with a location of the third opening corresponding to a location of the pressure sensing region.

Optionally, the preparing the second substrate may include: preparing a semiconductor-on-insulator substrate, where the semiconductor-on-insulator substrate includes a base, an insulating layer arranged on a surface of the base and a semiconductor layer arranged on a surface of the insulating layer; and forming a pressure-sensing electrode in the semiconductor layer, with the base being the second base.

Optionally, the second substrate may further include a second coupling layer arranged on the side of the third surface; or, the first substrate may include a first coupling layer arranged on the side of the first surface; or, the second substrate may further include a second coupling layer arranged on the side of the third surface and the first substrate may include a first coupling layer arranged on the side of the first surface.

Optionally, at least one of the first coupling layer and the second coupling layer is comprised of an insulating material.

Optionally, the first surface of the first substrate and the third surface of the second substrate may be bonded with each other by an adhesive bonding process, and the first coupling layer or the second coupling layer may be an adhesive bonding layer which is comprised of an insulating material, a semiconductor material, a metal material or an organic material.

Optionally, the first surface of the first substrate and the third surface of the second substrate may be bonded with each other by a direct-bonding process.

Optionally, the first substrate may further include a self-test electrode, with a location of the self-test electrode corresponding to a location of the pressure sensing region after the first surface of the first substrate and the third surface of the second substrate are bonded with each other.

Optionally, the second substrate may further include a reference unit region, a cavity may be formed between the first substrate and the reference unit region of the second substrate when the first surface of the first substrate and the third surface of the second substrate are bonded with each other, and a deformation on a portion of the second substrate corresponding to the reference unit region may be less than a deformation on a portion of the second substrate corresponding to the pressure sensing region under a same external pressure.

Optionally, the method may further include: forming a second opening passing through the first substrate, where a location of the second opening corresponds to a location of the pressure sensing region of the second substrate after the first surface of the first substrate and the third surface of the second substrate are bonded with each other.

Optionally, the method may further include: forming at least one fifth through hole passing through the second base, on the side of the fifth surface of the second substrate, with a location of the fifth through hole corresponding to a location of the pressure sensing region.

Optionally, the method may further include: forming a fourth conductive plug passing through the first substrate from the side of the second surface of the first substrate to the at least one conductive layer.

Accordingly, the present disclosure further provides a Micro-Electro Mechanical System (MEMS) pressure sensor. The MEMS pressure sensor includes: a first substrate, where the first substrate includes a first surface and a second surface opposite to the first substrate, and the first substrate includes at least one conductive layer arranged on the side of the first surface of the first substrate; a second substrate, where the second substrate includes a third surface and a fifth surface opposite to the third surface, the second substrate includes a pressure-sensing electrode, and the second substrate includes a pressure sensing region in which the pressure-sensing electrode is arranged, the first surface of the first substrate and the third surface of the second substrate are bonded with each other; a cavity formed between the first substrate and the pressure sensing region of the second substrate; and a first conductive plug passing through the second substrate from the side of the fifth surface of the second substrate to the at least one conductive layer, where the first conductive plug is used to electrically connect the conductive layer to the pressure-sensing electrode.

Optionally, the second substrate may further include a fixed electrode corresponding to the pressure-sensing electrode and the cavity may be formed between the pressure-sensing electrode and the fixed electrode.

Optionally, the first substrate may further include a fixed electrode arranged on the side of the first surface of the first substrate; the fixed electrode may correspond to the pressure-sensing electrode and the cavity may be formed between the pressure-sensing electrode and the fixed electrode.

Optionally, the first substrate may further include a circuit.

Optionally, the second substrate may further include a second coupling layer arranged on the side of the third surface; or, the first substrate may include a first coupling layer arranged on the side of the first surface; or, the second substrate may further include a second coupling layer arranged on the side of the third surface and the first substrate may include a first coupling layer arranged on the side of the first surface.

Optionally, at least one of the first coupling layer and the second coupling layer may be comprised of an insulating material.

Optionally, the first coupling layer or the second coupling layer may be an adhesive bonding layer which is comprised of an insulating material, a semiconductor material, a metal material or an organic material.

Optionally, the first coupling layer may be a bonding layer; or, the second coupling layer may be a bonding layer; or, the first coupling layer and the second coupling layer may be bonding layers.

Optionally, the first substrate may further include a self-test electrode, with a location of the self-test electrode corresponding to a location of the pressure sensing region of the second substrate.

Optionally, the second substrate may further include a reference unit region, a cavity may be formed between the first substrate and the reference unit region of the second substrate, and a deformation on a portion of the second substrate corresponding to the reference unit region may be less than a deformation on a portion of the second substrate corresponding to the pressure sensing region.

Optionally, the MEMS pressure sensor may further include: a second opening passing through the first substrate, with a location of the second opening corresponding to a location of the pressure sensing region of the second substrate.

Optionally, the MEMS pressure sensor may further include: a fourth conductive plug passing through the first substrate from the side of the second surface of the first substrate to the at least one conductive layer.

Accordingly, the present disclosure further provides a MEMS pressure sensor. The MEMS pressure sensor includes: a first substrate, where the first substrate includes a first surface and a second surface opposite to the first surface, and the first substrate includes at least one conductive layer arranged on the side of the first surface of the first substrate; a second substrate, where the second substrate includes a third surface and a fifth surface opposite to the third surface, the second substrate includes a second base and a pressure-sensing electrode arranged on or above or in the second base, and the second substrate includes a pressure sensing region in which the pressure-sensing electrode is arranged, the first surface of the first substrate and the third surface of the second substrate are bonded with each other; a cavity formed between the first substrate and the pressure sensing region of the second substrate; and a first conductive plug passing through the second substrate from the side of the fifth surface of the second substrate to the at least one conductive layer, where the first conductive plug is used to electrically connect the conductive layer to the pressure-sensing electrode.

Optionally, the second substrate may further include a fixed electrode corresponding to the pressure-sensing electrode and the cavity may be formed between the pressure-sensing electrode and the fixed electrode.

Optionally, the first substrate may further include a fixed electrode arranged on the side of the first surface of the first substrate; the fixed electrode may correspond to the pressure-sensing electrode and the cavity may be formed between the pressure-sensing electrode and the fixed electrode.

Optionally, the first substrate may further include a circuit.

Optionally, a third opening may be formed in the second substrate, with a location of the third opening corresponding to a location of the pressure sensing region.

Optionally, the second substrate may further include a second coupling layer arranged on the side of the third surface; or, the first substrate may include a first coupling layer arranged on the side of the first surface; or, the second substrate may further include a second coupling layer arranged on the side of the third surface and the first substrate may include a first coupling layer arranged on the side of the first surface.

Optionally, at least one of the first coupling layer and the second coupling layer may be comprised of an insulating material.

Optionally, the first coupling layer or the second coupling layer may be an adhesive bonding layer which is comprised of an insulating material, a semiconductor material, a metal material or an organic material.

Optionally, the first coupling layer may be a bonding layer; or, the second coupling layer may be a bonding layer; or, the first coupling layer and the second coupling layer may be bonding layers.

Optionally, the first substrate may further include a self-test electrode, with a location of the self-test electrode corresponding to a location of the pressure sensing region of the second substrate.

Optionally, the second substrate may further include a reference unit region, a cavity may be formed between the first substrate and the reference unit region of the second substrate, and a deformation on a portion of the second substrate corresponding to the reference unit region may be less than a deformation on a portion of the second substrate corresponding to the pressure sensing region.

Optionally, a second opening passing through the first substrate may be formed, with a location of the second opening corresponding to a location of the pressure sensing region of the second substrate.

Optionally, the MEMS pressure sensor may further include: at least one fifth through hole arranged on the side of the fifth surface of the second substrate and passing through the second base, with a location of the fifth through hole corresponding to a location of the pressure sensing region.

Optionally, the MEMS pressure sensor may further include: a fourth conductive plug passing through the first substrate from the side of the second surface of the first substrate to the at least one conductive layer.

Compared with the conventional technologies, technical solutions of the present disclosure have the following advantages.

In a fabrication method according to the present disclosure, a first substrate including a conductive layer and a second substrate including a pressure-sensing electrode are prepared. The conductive layer is arranged on the side of a first surface of the first substrate, and the pressure-sensing electrode is arranged on the side of a third surface of the second substrate. A stacked structure of the first substrate and second substrate can be formed by bonding the first surface of the first substrate and the third surface of the second substrate with each other. The conductive layer may be used to transmit an electrical signal output by a capacitor including the pressure-sensing electrode. After the second base is removed and a fifth surface opposite to the third surface is formed, a first conductive plug passing through the second substrate from the fifth surface of the second substrate to the conductive layer is formed to electrically connect the conductive layer and the capacitor including the pressure-sensing electrode. Since the first conductive plug is exposed in the fifth surface of the second substrate, it is easy to form subsequently a first conductive structure, which is electrically connected to the pressure-sensing electrode, at the top of the first conductive plug, and thus the pressure-sensing electrode is electrically connected to the conductive layer.

The conductive layer is formed in the first substrate, the pressure-sensing electrode is formed in the second substrate, and the first substrate is stacked with the second substrate by bonding the first surface of the first substrate and the third surface of the second substrate with each other. Therefore, it is avoided to form a conductive layer, a fixed electrode, a pressure-sensing electrode corresponding to the fixed electrode and a cavity between the pressure-sensing electrode and the base in a layer by layer manner on a single base, thereby reducing the difficulty of process and, in particular, reducing the difficulty of a process for forming the cavity. Furthermore, it can be avoided that a temperature in a process for forming the first substrate limits or affects a fabrication process of the second substrate. In this case, selection of materials and processes for the second substrate and the pressure-sensing electrode in the second substrate is more flexible, and the performance of the formed pressure-sensing electrode is improved.

Since the first surface of the first substrate is in contact with the third surface of the second substrate, a contact area between the first surface and the third surface is large and a bonding strength between the first substrate and the second substrate is high. In this case, it is not easy to bend, break or deform a stacked structure of the first substrate and the second substrate, thereby providing a more stable and reliable structure of the formed pressure sensor and improving the durability of the formed pressure sensor.

With the above method, the distance between the fourth surface of the second substrate and the second surface of the first substrate is short, thereby reducing the size and the fabrication cost of the formed pressure sensor.

Besides, since the conductive layer is electrically connected to the capacitor including the pressure-sensing electrode by forming a first conductive plug passing through the second substrate from the fifth surface of the second substrate to the conductive layer, no additional conductive layer is necessary between the first surface of the first substrate and the third surface of the second substrate for the purpose of providing electrical connection, avoiding any negative impact that could be generated by the additional conductive layer. Since the selection of materials of the first surface of the first substrate and the third surface of the second substrate is more flexible, an excessive thermal expansion coefficient mismatch between the material of the first surface and the material of the third surface can be avoided, and the performance of the formed pressure sensor can be made more stable. Since the processes for forming the first substrate and the second substrate are more independent, the fabrication process of the pressure sensor is more compatible with various fabrication processes of integrated conductive layer, thereby reducing the fabrication cost.

Further, the second substrate may include a fixed electrode corresponding to the pressure-sensing electrode. A cavity is formed between the pressure-sensing electrode and the fixed electrode. A capacitive type pressure sensor is formed with the pressure-sensing electrode, the fixed electrode and the cavity. If a pressure is applied to the pressure-sensing electrode, a capacitance of the capacitor formed with the pressure-sensing electrode, the fixed electrode and the cavity may change, and thus an electrical signal changing with the pressure changing is outputted.

Further, the first substrate may include a fixed electrode. A first opening is formed from the third surface of the second substrate. When the first surface of the first substrate and the third surface of the second substrate are bonded with each other, a cavity is formed between the pressure-sensing electrode and the fixed electrode with the first opening and the first surface of the first substrate. The capacitive type pressure sensor is formed with pressure-sensing electrode, the fixed electrode and the cavity.

Further, the first substrate includes a circuit. An electrical signal output by the capacitor including the pressure-sensing electrode can be readily processed by the circuit since the first substrate is bonded and electrically coupled with the second substrate.

Further, the second substrate is formed by preparing a semiconductor-on-insulator substrate. Specifically, a pressure-sensing electrode can be formed by patterning a semiconductor layer in the semiconductor-on-insulator substrate. The pressure-sensing electrode may be deformed under a pressure, which leads to a change of a capacitance between the pressure-sensing electrode and the fixed electrode, thereby outputting an electrical signal related to the pressure on the pressure-sensing electrode. Since the semiconductor layer in the semiconductor-on-insulator substrate is comprised of a single crystal semiconductor material, a pressure-sensing electrode formed by doping ions into the single crystal semiconductor material has a good pressure-sensing property, thereby improving the sensitivity and the stability of the formed pressure-sensing electrode.

Further, a first opening is formed from the third surface of the second substrate or the first surface of the first substrate; or, first openings are formed from the first surface and the third surface. A cavity between the pressure-sensing electrode and fixed electrode is formed by the first opening and the first surface of the first substrate when the first surface of the first substrate and the third surface of the second substrate are bonded with each other. The first surface contacts with the third surface in a large area other than a location of the first opening. Therefore, a total thickness of the bonded first and second substrates is small, a mechanical strength of the stacked structure of the first substrate and the second substrate is high and the performance of the formed pressure sensor is improved.

Further, the first substrate may further include a self-test electrode. A location of the self-test electrode corresponds to a location of the pressure-sensing electrode after the first surface of the first substrate and the third surface of the second substrate are bonded with each other. The self-test electrode can generate an electrostatic pulling force and therefore a deformation on the pressure-sensing electrode. A capacitance changing in the pressure-sensing electrode due to this deformation can be used to detect whether the pressure-sensing electrode works normally.

Further, the second substrate includes a sensing unit region and a reference unit region, and cavities are formed in the sensing unit region and the reference unit region. For example, a cover layer may be formed on a portion of the fifth surface of the second substrate corresponding to the reference unit region. In this case, a deformation of the pressure-sensing electrode in the reference unit region due to an external pressure can be avoided or reduced, however, a capacitance of the pressure-sensing electrode in the reference unit region may change due to a factor other than pressure. An electrical signal generated due to the external pressure can be obtained by subtracting the electrical signal output by the pressure-sensing electrode in the reference unit region from an electrical signal output by the pressure-sensing electrode in the sensing unit region. Therefore, the accuracy of the formed pressure sensor is improved.

Further, a second opening in the first substrate is formed. A location of the second opening corresponds to a location of the pressure sensing region after the first surface of the first substrate and the third surface of the second substrate are bonded with each other. Since the second opening is exposed to an external environment, two sides of a pressure-sensing electrode can acquire pressures from the external environment and the pressure-sensing electrode can acquire a signal representing a difference between the pressures on the two sides of the pressure-sensing electrode. In this case, the formed pressure sensor can serves as a differential pressure sensor.

In another fabrication method according to the present disclosure, a first substrate including a conductive layer and a second substrate including a pressure-sensing electrode are prepared. A stacked layer structure of the first and second substrates can be formed by bonding a first surface of the first substrate and a third surface of the second substrate with each other. The conductive layer can transmit an electrical signal output from a capacitor including the pressure-sensing electrode. In order to electrically connect the conductive layer to the pressure-sensing electrode, a first conductive plug passing through the second substrate from a fifth surface of the second substrate to the conductive layer is formed after a second base is thinned partially and the fifth surface is formed. Since the first conductive plug is exposed in the fifth surface of the second substrate, it is easy to form subsequently a first conductive structure, which is electrically connected to the pressure-sensing electrode, at the top of the first conductive plug, and thus the pressure-sensing electrode is electrically connected to the conductive layer. Since the first surface is in contact with the third surface in a large area, the mechanical strength of the stacked structure of the first substrate and the second substrate is high and the formed pressure sensor has a stable structure and an improved durability. In addition, the size of the formed pressure sensor is small since a distance between the fifth surface of the second substrate and a second surface of the first substrate is short. Since the selection of materials of the first surface and a third surface is more flexible, an excessive thermal expansion coefficient mismatch between the material of the first surface and the material of the third surface can be avoided, and the performance of the formed pressure sensor can be made more stable.

Further, the second substrate includes a third opening, with a location of the third opening corresponding to a location of the pressure sensing region. Since regions other than the pressure sensing region are covered by the second base, a distance from the pressure-sensing electrode to the external environment may be increased while the pressure-sensing electrode acquires an external pressure, thereby protecting the pressure-sensing electrode and avoiding a wear or other damages on the pressure-sensing electrode and a protective layer on a surface of the pressure-sensing electrode.

A structure according to the present disclosure includes a first substrate including a conductive layer and a second substrate including a pressure-sensing electrode. The conductive layer is arranged on the side of a first surface of the first substrate. The first surface of the first substrate and a third surface of the second substrate are bonded with each other. Therefore, the first substrate and the second substrate are stacked with each other, and the conductive layer is used to transmit an electrical signal output from a capacitor including the pressure-sensing electrode. A first conductive plug passing through the second substrate from a fifth surface of the second substrate to the conductive layer is formed, and hence the pressure-sensing electrode can be electrically connected to the conductive layer via the first conductive plug and a first conductive structure. Since the first surface is in contact with the third surface in a large area, a mechanical strength of the stacked structure of the first substrate and the second substrate is high and the formed pressure sensor has a stable structure and an improved durability. In addition, the size of the formed pressure sensor is small since a distance between a fifth surface of the second substrate and a second surface of the first substrate is short. Since the selection of materials of the first surface and the third surface is more flexible, an excessive thermal expansion coefficient mismatch between the material of the first surface and the material of the third surface can be avoided, and the performance of the formed pressure sensor can be made more stable.

Another structure according to the present disclosure includes a first substrate including a conductive layer, and a second substrate including a second base and a pressure-sensing electrode arranged on or above the second base. The conductive layer is arranged on the side of a first surface of the first substrate, and the pressure-sensing electrode is arranged on the side of a third surface of the second substrate. Since the first surface of the first substrate and the third surface of the second substrate are bonded with each other, the first substrate is stacked with the second substrate, and the conductive layer is used to transmit an electrical signal output from a capacitor including the pressure-sensing electrode. The pressure-sensing electrode can be protected by the second base since the second base is arranged on the side of a fifth surface of the second substrate. In addition, a first conductive plug passing through the second substrate from the fifth surface of the second substrate to the conductive layer is formed, and hence the capacitor including the pressure-sensing electrode can be electrically connected to the conductive layer via the first conductive plug and a first conductive structure. Since the first surface is in contact with the third surface in a large area, the mechanical strength of the first and second substrates is high and the formed pressure sensor has a stable structure and an improved durability. Furthermore, no extra space exists between the first surface of the first substrate and the third surface of the second substrate, and a distance between the fifth surface of the second substrate and a second surface of the first substrate is short, and hence the size of the formed pressure sensor is small. Since the selection of materials of the first surface and a third surface is more flexible, an excessive thermal expansion coefficient mismatch between the material of the first surface and the material of the third surface can be avoided, and the performance of the formed pressure sensor can be more stable.

DETAILED DESCRIPTION OF EMBODIMENTS

As described in the Background, in the existing methods for fabricating a MEMS capacitive type pressure sensor, a process of integrating a pressure sensor chip with a signal processing circuit is complicated and the size of the formed device is large.

In an existing method for fabricating a MEMS capacitive type pressure sensor, a pressure sensor chip and a signal processing circuit chip are fabricated separately, and then are placed on a packaging substrate having a cavity, and are connected to each other using a wirebonding lead. The sensor chip and the signal processing circuit chip after being connected to each other are coated with a layer of protective gel, hence to be surrounded by the protective gel. After the protective gel is coated, a plastic or metal cover is placed outside the protective gel for cover/sealing. In another existing embodiment, the pressure sensor chip and the signal processing circuit chip may be placed on a flat packaging substrate and are connected to each other using the wirebonding lead, and then the pressure sensor chip and the signal processing circuit chip are coated with a layer of protective soft gel and are covered with a metal shell.

However, in fabricating the above MEMS capacitive type pressure sensor, the pressure sensor chip and the signal processing circuit chip are arranged separately side by side on a surface of the packaging substrate. In this case, the formed MEMS pressure sensor has a large size, which can not meet advanced miniaturization requirement for the MEMS pressure sensors. Furthermore, after being placed on the packaging substrate, the pressure sensor chip and the signal processing circuit chip have to be protected using the protective gel and covered with the plastic or metal cover, the fabrication process is complicated and it is not easily compatible with monolithic integration using various integrated circuit fabrication processes.

In order to address the above issue, the present disclosure provides a MEMS capacitive type pressure sensor and a method for forming the MEMS capacitive type pressure sensor. In the method, a first substrate including a conductive layer and a second substrate including a pressure-sensing electrode are prepared. The conductive layer is arranged on the side of a first surface of the first substrate and the pressure-sensing electrode is arranged on the side of a third surface of the second substrate. A stacked structure of the first and second substrates may be formed by bonding the first surface of the first substrate and the third surface of the second substrate with each other. The conductive layer may be used to transmit an electrical signal output from a capacitor including the pressure-sensing electrode. After a second base is removed or thinned and a fifth surface opposite to the third surface is formed, a first conductive plug passing through the second substrate from the fifth surface of the second substrate to the conductive layer is formed to electrically connect the conductive layer and the capacitor including the pressure-sensing electrode. Since the first conductive plug is exposed in the fifth surface of the second substrate, it is easy to subsequently form a first conductive structure, which is electrically connected to the pressure-sensing electrode, at the top of the first conductive plug, and thus the pressure-sensing electrode is electrically connected to the conductive layer.

The conductive layer is formed in the first substrate, and the pressure-sensing electrode is formed in the second substrate. The first substrate is stacked with the second substrate by bonding the first surface of the first substrate and the third surface of the second substrate with each other. In this case, it is avoided to form the conductive layer, a fixed electrode, the pressure-sensing electrode corresponding to the fixed electrode and a cavity between the pressure-sensing electrode and the fixed electrode in a layer by layer manner on a single base, thereby reducing a difficulty of processes and, in particular, reducing a difficulty of a process for forming the cavity. In addition, it is avoided that a temperature for forming the first substrate limits or affects a fabrication process of the second substrate. In this case, selection of materials and processes for the second substrate and the pressure-sensing electrode is more flexible, and the sensitivity of the formed pressure-sensing electrode is improved.

Since the first surface of the first substrate bonds with the third surface of the second substrate in a large area, the overall strength of a stacked structure of the first substrate and the second substrate is high. In this case, it is not easy to bend, break or deform the stacked structure of the first substrate and the second substrate, thereby improving the reliability of the structure of the formed pressure sensor and improving the durability of the formed pressure sensor.

With the above method, a distance between the fifth surface of the second substrate and the second surface of the first substrate is short, thereby reducing the size and a fabrication cost of the formed pressure sensor.

Furthermore, since the conductive layer is electrically connected to the capacitor including the pressure-sensing electrode by forming the first conductive plug passing through the second substrate from the fifth surface of the second substrate to the conductive layer, no additional conductive layer is necessary between the first surface of the first substrate and the third surface of the second substrate for the purpose of providing electrical connection, avoiding any negative impact that could be generated by the additional conductive layer. In addition, the selection of materials of the first surface of the first substrate and the third surface of the second substrate is more flexible, an excessive thermal expansion coefficient mismatch between the material of the first surface and the material of the third surface can be avoided, and the performance of the formed pressure sensor can be made more stable. Since the processes for forming the first substrate and the second substrate are more independent, the fabrication process of the pressure sensor is more compatible with various integrated circuit fabrication processes, thereby reducing the fabrication cost.

In the following, specific embodiments of the present disclosure are described in detail in conjunction with the drawings, to make the above objectives, properties and advantages of the present disclosure more apparent.

First Embodiment

FIGS. 1 to 9are schematic cross-sectional diagram of a MEMS pressure sensor in a fabrication process according to an embodiment of the present disclosure.

Referring toFIG. 1, a first substrate100is prepared. The first substrate100includes a first surface101and a second surface102opposite to the first surface101. The first substrate100includes at least one conductive layer103arranged on the side of the first surface101of the first substrate100.

In the embodiment, the first substrate100further includes a fixed electrode140arranged on the side of the first surface101of the first substrate100. When the first surface101of the first substrate100and a third surface of a second substrate are bonded with each other, the fixed electrode140is arranged opposite to a pressure-sensing electrode, a cavity is formed between the pressure-sensing electrode and the fixed electrode, and a pressure-sensing capacitor structure can be formed with the pressure-sensing electrode, the fixed electrode and the cavity. A capacitance of the pressure-sensing capacitor structure may change with a change of a pressure applied on the pressure-sensing electrode. In another embodiment, the fixed electrode may be formed in the second substrate.

The first substrate100is used to form the conductive layer103, and the conductive layer103is used to transmit an electrical signal output from a capacitor including a pressure-sensing electrode.

In the embodiment, the first substrate100includes a first base104, a first dielectric layer105arranged on a surface of the first base104, the conductive layer103arranged on a surface of the first dielectric layer105, and a first coupling layer106arranged on the side of the first surface101. In the embodiment, the conductive layer103has a single layer structure. In another embodiment, the conductive layer may include multiple conductive layers. In this case, a first conductive plug subsequently formed may be connected to at least one conducive layer. In another embodiment, the first substrate100may not include the first coupling layer106.

The first base104includes a silicon substrate, a silicon germanium substrate, a silicon carbide substrate, a glass substrate or an III-V group compound substrate (such as a gallium nitride substrate or a gallium arsenide substrate).

The first dielectric layer105is used to electrically isolate the conductive layer103from the first base104. The first dielectric layer105may be comprised of silicon oxide, silicon nitride, silicon oxynitride, a low-k dielectric material (material with a dielectric constant in a range from 2.5 to 3.9) or an ultra low-k dielectric material (material with a dielectric constant less than 2.5). The first dielectric layer105may be formed by an oxidation process, a chemical vapor deposition process, a physical vapor deposition process or an atomic layer deposition process.

The conductive layer103may be comprised of a conductive material including a metal material, a metal compound material or a semiconductor material doped with ions. The process of forming the conductive layer103includes: depositing a conductive material layer on a surface of the first dielectric layer105; forming a patterned layer on a surface of the conductive material layer, with a portion of the surface of the conductive material layer being exposed from the patterned layer; and etching the conductive material layer with the patterned layer being a mask until the first dielectric layer105is exposed. The conductive material layer may be formed by a chemical vapor deposition process, a physical vapor deposition process or an atomic layer deposition process. The patterned layer is a patterned photoresist layer. The conductive material layer may be etched with a dry etching process.

The process of forming the fixed electrode140includes: depositing a second electrode layer on a surface of the first dielectric layer105; forming a patterned layer on a surface of the second electrode layer, with a portion of the surface of the second electrode layer being exposed from the patterned layer; and etching the second electrode layer with the patterned layer being a mask until the surface of the first dielectric layer105is exposed. The second electrode layer may be formed by a chemical vapor deposition process, a physical vapor deposition process or an atomic layer deposition process. The patterned layer includes a patterned photoresist layer, and the conductive material layer may be etched with a dry etching process.

In the embodiment, the fixed electrode140and the conductive layer103are arranged in a same layer and formed simultaneously. The fixed electrode140may be comprised of a metal material, a metal compound material or a semiconductor material doped with ions. In another embodiment, the fixed electrode may be formed before or after the conductive layer is formed, and the fixed electrode and the conductive layer may be arranged in different layers.

The first coupling layer106protects the conductive layer103, and is to be bonded with a second coupling layer of a surface of a second substrate subsequently, to bond the first substrate100and the second substrate with each other. The first coupling layer106has a flat surface, that is, the first surface101of the first substrate100is flat. A third surface of the second substrate prepared subsequently is also flat. In this case, a contact area between the first surface101and the third surface is large after the first surface101of the first substrate100and the third surface of the second substrate are bonded, the strength of a stacked structure of the first surface101and the second substrate is high and the first surface101is bonded with the second substrate stably.

The first coupling layer106may be comprised of one or more of an insulating material, a metal material, a metal compound material and a semiconductor material. The insulating material includes silicon oxide, silicon nitride, silicon oxynitride, a low-k dielectric material or an ultra low-k dielectric material. The metal material includes one or more of copper, tungsten, aluminum, silver, titanium and tantalum. The metal compound material includes one or two of titanium nitride and tantalum nitride. The semiconductor material includes one or more of polycrystalline silicon, amorphous silicon, polycrystalline germanium, amorphous germanium, silicon germanium and silicon carbide which are doped with ions. The ions being doped include one or more of p-type ions, n-type ions, carbon ions, nitrogen ions, fluoride ions and hydrogen ions.

In an embodiment, the first coupling layer106is comprised of silicon oxide. The process of forming the first coupling layer includes: depositing a first coupling film partially on a surface of the first dielectric layer105and partially on a surface of the conductive layer103; and forming the first coupling layer106by flatting the first coupling film with a chemical mechanical polishing process.

In another embodiment, the first substrate100may not include the first coupling layer and the second substrate prepared subsequently may include a second coupling layer.

In addition, the first substrate100further includes a circuit including a semiconductor device structure and an electrical interconnection structure. The conductive layer103may be one of conductive layers of the circuit, or, may be a conductive layer added to the circuit. The conductive layer103may include a conductor or a semiconductor.

In the embodiment, a second substrate is prepared. The second substrate includes a third surface and a fourth surface opposite to the third surface. The second substrate includes a second base and a pressure-sensing electrode arranged on or above the second base. The pressure-sensing electrode is arranged on the side of the third surface of the second substrate. In the following, a fabrication process of the second substrate is described.

Referring toFIG. 2, a second base110, a protective layer111arranged on a surface of the second base110and a first electrode layer112arranged on a surface of the protective layer111are prepared.

In an embodiment, the second base110, the protective layer11and the first electrode layer112are formed with a semiconductor-on-insulator substrate. Specifically, the semiconductor-on-insulator substrate is prepared, where the semiconductor-on-insulator substrate includes a base, an insulating layer arranged on a surface of the base and a semiconductor layer arranged on a surface of the insulating layer. The base is the second base110and the insulating layer is the protective layer111.

The semiconductor-on-insulator substrate includes a silicon-on-insulator substrate. The protective layer may be comprised of silicon oxide, i.e. buried oxide layer (BOX). The first electrode layer112may be comprised of monocrystalline silicon or monocrystalline germanium. Since the first electrode layer112may be comprised of monocrystalline silicon material which is doped with doping ions, a capacitance of the capacitor including the pressure-sensing electrode may change more due to a deformation of the pressure-sensing electrode, that is, the sensitivity of the formed pressure-sensing electrode is improved and the performance of the formed pressure-sensing electrode is more stable and reliable. In addition, in a case that the semiconductor layer of the semiconductor-on-insulator substrate directly serves as the first electrode layer112and the insulating layer serves as the protective layer111, it is unnecessary to form a first electrode layer112and a protective layer111by an additional deposition process, thereby simplify the fabrication process.

In another embodiment, the second base110is a body base. The body base includes a silicon substrate, a silicon germanium substrate, a silicon carbide substrate, a glass substrate or an III-V group compound substrate (such as a gallium nitride substrate or a gallium arsenide substrate).

The protective layer111and the first electrode layer112are formed by a deposition process including a physical vapor deposition process, a chemical vapor deposition process or atomic layer deposition process. The protective layer111may be comprised of an insulating material such as silicon oxide, silicon nitride, silicon oxynitride, a low-k dielectric material or an ultra low-k dielectric material. The first electrode layer112may be comprised of a semiconductor material such as polycrystalline silicon, amorphous silicon, polycrystalline germanium, amorphous germanium, silicon carbide, gallium arsenide and silicon germanium. Besides, the first electrode layer112may be comprised of metal or metal compound including one or more of copper, tungsten, aluminum, silver, titanium, tantalum, titanium nitride and tantalum nitride.

Since the second base110is a body base, and the protective layer111and the first electrode layer112are formed by a deposition process, the second base110, the protective layer111and the first electrode layer112may be comprised of materials of variety of selections, and meets more fabrication process needs.

Referring toFIG. 3, the first electrode layer112(as shown inFIG. 2) is etched to form a pressure-sensing electrode113.

In the embodiment, the second substrate114includes the second base110, the first electrode layer112and a pressure sensing region180in which the pressure-sensing electrode113is arranged. In addition, an electrode interconnection layer may be formed by etching the first electrode layer112, and the electrode interconnection layer is electrically connected to the pressure-sensing electrode113. A pressure sensing film is formed in the pressure sensing region180of the second substrate114.

The process of forming the pressure-sensing electrode113includes: forming a first patterned layer on a surface of the first electrode layer112, with a portion of the surface of the first electrode layer112being exposed from the first patterned layer; etching the first electrode layer112with the first patterned layer being a mask until the surface of the protective layer111is exposed, to form a pressure-sensing electrode113; and removing the first patterned layer after the first electrode layer is etched.

The first patterned layer is a patterned photoresist layer formed by a photolithography process. Alternatively, the first patterned layer may be a mask formed by a multi-pattern mask process, such as a Self-Aligned Double Patterning (abbreviated to SADP) mask. The first patterned layer may be removed with a dry etching process or a wet etching process.

The first electrode layer112may be etched by an anisotropic dry etching process. In the embodiment, the first electrode layer112is etched until the surface of the protective layer111is exposed.

In the embodiment, the fixed electrode140in the first substrate100(as shown inFIG. 1) and the pressure-sensing electrode113serve as electrodes of a capacitor in the formed capacitive type pressure sensor. The pressure-sensing electrode113can be deformed with a change of a pressure on the pressure-sensing electrode113, and thus a capacitance between the pressure-sensing electrode113and the fixed electrode140changes and an output electrical signal changes.

Referring toFIG. 4, a second coupling layer117is formed on the side of the third surface of the second substrate114.

In the embodiment, the second substrate114includes the second base110, the protective layer111, the pressure-sensing electrode113and the second coupling layer117. The second substrate114includes a third surface118and a fourth surface119, the third surface118is a surface of the second coupling layer117and the fourth surface119is a surface of the second base110. In addition, the second substrate114includes a pressure sensing region180in which the pressure-sensing electrode113is arranged.

In the embodiment, the second coupling layer117is arranged on a surface of the pressure-sensing electrode113and a surface of the protective layer111. The second coupling layer117is used to protect the pressure-sensing electrode113. The second coupling layer117is bonded with the first coupling layer106(as shown inFIG. 1) to bond the first substrate100(as shown inFIG. 1) and the second substrate114with each other. The surface of the second coupling layer117is flat, that is, the third surface118of the second substrate114is flat. In another embodiment, only the first substrate100includes the first coupling layer106, or only the second substrate114includes the second coupling layer117.

The second coupling layer117may be comprised of one or more of an insulating material, a metal material, a metal compound material and a semiconductor material. The insulating material includes silicon oxide, silicon nitride, silicon oxynitride, a low-k dielectric material or an ultra low-k dielectric material. The metal material includes one or more of copper, tungsten, aluminum, silver, titanium and tantalum. The metal compound material includes one or two of titanium nitride and tantalum nitride. The semiconductor material includes one or more of polycrystalline silicon, amorphous silicon, polycrystalline germanium, amorphous germanium, silicon germanium and silicon carbide which are doped with ions. The ions being doped include one or more of p-type ions, n-type ions, carbon ions, nitrogen ions, fluoride ions and hydrogen ions.

In an embodiment, the second coupling layer117may be comprised of silicon oxide. The process of forming the second coupling layer117includes: depositing a second coupling film partially on the surface of the protective layer111and partially on the surface of the pressure-sensing electrode113; and forming a second coupling layer117by flattening the second coupling film by a chemical mechanical polishing process.

In the embodiment, at least one of the first coupling layer106and the second coupling layer117may be comprised of an insulating material. Alternatively, both the surface of the first coupling layer106and the surface of the second coupling layer117may be comprised of an insulating material. In the embodiment, after the first substrate100and the second substrate114are bonded with each other, a first conductive plug passing through the second substrate114from a fifth surface of the second substrate114to a surface of the conductive layer103is formed, and the conductive layer103can be electrically connected to the pressure-sensing electrode113via the first conductive plug and a subsequently formed first conductive structure. Therefore, no additional conductive layer is formed between a surface of the first coupling layer106and a surface of the second coupling layer117which are in contact with each other. In this case, the first coupling layer106and the second coupling layer117may be comprised of various types of material, and meets more fabrication process needs.

In another embodiment, the second substrate may not include a second coupling layer and the first substrate100includes a first coupling layer.

In another embodiment, a fixed electrode is formed in the second substrate. The fixed electrode is arranged in the pressure sensing region and opposite to the pressure-sensing electrode. A cavity is formed between pressure-sensing electrode and the fixed electrode. In the embodiment, it is unnecessary to form a fixed electrode in the first substrate.

Before the second coupling layer is formed, a second dielectric layer is formed on a surface of the pressure-sensing electrode113. A fixed electrode is formed on a surface of the second dielectric layer. A cavity is formed by removing a portion of the second dielectric layer between the fixed electrode and the pressure-sensing electrode. In an embodiment, a second coupling layer is formed partially on the surface of the second dielectric layer and partially on a surface of the fixed electrode after the cavity is formed. In another embodiment, the second coupling layer may not be formed.

The process of forming the second dielectric layer includes: depositing a second dielectric film partially on the surface of the pressure-sensing electrode113and partially on the surface of the protective layer111; and flattening the second dielectric film to form a second dielectric layer. The second dielectric layer may be comprised of silicon oxide, silicon nitride, silicon oxynitride, a low-k dielectric material or an ultra low-k dielectric material. The second dielectric film may be filmed by a chemical vapor deposition process, a physical vapor deposition process or an atomic layer deposition process. The second dielectric film is flattened by the chemical mechanical polishing process.

The cavity may be formed by an etching process including an isotropic etching process, and the isotropic etching process may be a wet etching process or a dry etching process. Etching rates of the isotropic etching process in various directions are similar to one another. Therefore, the second dielectric layer may be etched in a direction parallel to the surface of the second substrate to remove a portion of the second dielectric layer between the fixed electrode and the pressure-sensing electrode. Several through holes may be formed in the fixed electrode to expose a portion of a surface of the second dielectric surface. The portion of second dielectric layer at the bottom of the through hole is etched in the etching process for forming the cavity, to remove the portion of the second dielectric layer between the fixed electrode and the pressure-sensing electrode.

Referring toFIG. 5, a first opening120is formed from the third surface118of the second substrate114, and a location of the first opening120corresponds to a location of the pressure pressure-sensing electrode113.

In the embodiment, since the fixed electrode140(as shown inFIG. 1) is formed in the first substrate100(as shown inFIG. 1), the first opening120is formed from the third surface118of the second substrate114. When the first substrate100and the second substrate114are bonded, a cavity is formed between the third surface118and the first surface101of the first substrate100. A pressure in the cavity may be one atmospheric pressure or other preset pressure values. The cavity may serve as a dielectric between the pressure-sensing electrode113and the fixed electrode. A capacitance value of a capacitor structure formed with the cavity, the pressure-sensing electrode113and the fixed electrode140(as shown inFIG. 1) may change in a case that the pressure-sensing electrode113is deformed under an pressure, thereby outputting an electrical signal changing as the pressure or stress changes.

The process of forming the first opening120includes: forming a patterned layer on a surface of the second coupling layer117; and etching the second coupling layer117with the patterned layer being a mask to form a first opening120in the second coupling layer117. The patterned layer may be a patterned photoresist layer. The etching process may be a dry etching process, a wet etching process or a combination thereof.

In the embodiment, the surface of the pressure-sensing electrode113is exposed at the bottom of the first opening120. In another embodiment, the surface of the pressure-sensing electrode113is not exposed at the bottom of the first opening120, and the pressure-sensing electrode113is protected.

In another embodiment, the first opening may be formed on the side of the first surface of the first substrate, and a location of the first opening corresponds to the location of a pressure sensing region of the second substrate. In another embodiment, first openings may be formed on the side of the first surface of the first substrate and the side of a third surface of the second substrate, with locations of the first openings corresponding to the location of the pressure sensing region.

Reference is made toFIG. 6. The first surface101of the first substrate100and the third surface118of the second substrate are bonded with each other, and a cavity121is formed between the first substrate100and the pressure sensing region180of the second substrate114.

In the embodiment, since the first opening120is formed from the third surface118of the second substrate114(as shown inFIG. 5), the cavity121is formed with the first opening120and the first surface101of the first substrate100when the first surface101of the substrate100and the third surface118of the second substrate114are bonded with each other.

In another embodiment, a first opening may be formed by etching the first surface101of the first substrate100, with a location of the first opening corresponding to the pressure sensing region180in the second substrate114. In this case, a cavity121is formed with the first opening and the third surface118of the second substrate114when the first surface101of the first substrate100and the third surface118of the second substrate are bonded with each other.

In an embodiment, the first substrate100and the second substrate114may be bonded with a direct-bonding process such as Fusion Bonding, Anodic Bonding, Eutectic Bonding or Thermal Compression Bonding. In another embodiment, the first substrate100and the second substrate114may be bonded with each other by an adhesive bonding process, and the first substrate100and the second substrate114are bonded with an adhesive bonding layer. The adhesive bonding layer may be comprised of an insulating material, a semiconductor material, a metal material or an organic material. The first coupling layer or the second coupling layer serves as the adhesive bonding layer.

In the embodiment, the surface of the first coupling layer106is flat, and the surface of the second coupling layer117is flat. The surface of the first coupling layer106is the first surface of the first substrate100and the surface of the second coupling layer117is the third surface of the second substrate114. The surface of the first coupling layer106is in contact and bonded with the surface of the second coupling layer117, so that the first substrate100and the second substrate114can be stacked and bonded with each other.

The cavity121between the first substrate100and the pressure sensing region180of the second substrate114is formed as a pressure reference chamber, in a case that the first substrate100and the second substrate114are bonded with each other. A pressure in the formed cavity121can be adjusted by adjusting an ambient pressure in bonding the first substrate100and the second substrate114. After the second base110is removed, a pressure difference exists between a pressure applied to a surface of the protective layer111and the pressure in the cavity121. The pressure-sensing electrode113is deformed due to the pressure difference. The deformation leads to a change in the capacitance between the pressure-sensing electrode113and the fixed electrode140, which leads to a change in an electrical signal output from the capacitor structure formed by the pressure-sensing electrode113and the fixed electrode. Therefore, an output electrical signal changes with a change in the pressure difference between the external pressure and the pressure in the cavity121, and an external pressure signal is detected.

Since the first surface101of the first substrate100is in contact with the third surface118of the second substrate114, and the first surface101and the third surface118are flat, the first surface101is in contact with the third surface118in a large area, a bonding strength between the first substrate100and the second substrate114is high, and it is not easy to bend, break or deform a stacked structure of the first substrate100and the second substrate114, thereby providing a more stable and reliable structure of the formed pressure sensor and improving the durability of the formed pressure sensor.

Furthermore, except for the formed cavity121, the first surface101of the first substrate100mostly is in contact with the third surface118of the second substrate114, and there is no extra space between the first surface101and the third surface118. In this case, a distance from the fourth surface119of the second substrate114to the second surface102of the first substrate100is short, thereby reducing a thickness and a size of the formed MEMS pressure sensor and improving device integration.

In addition, no additional conductive layer is necessary between the first surface101of the first substrate100and the third surface118of the second substrate114, since the conductive layer103is electrically connected to the pressure-sensing electrode113by forming the first conductive plug passing through the second substrate114from the fifth surface of the second substrate114to the conductive layer103. In this way, no excess stress is generated between the first surface101and the third surface118due to a thermal expansion coefficient mismatch, thereby ensuring the accuracy of the electrical signal output from the capacitor including the pressure-sensing electrode113.

The selection of materials of the first surface101of the first substrate100and the third surface118of the second substrate114is flexible, and hence the first surface101and the third surface118may be comprised of material with a small thermal expansion coefficient mismatch. In this case, no or minimal stress is generated due to the excessive thermal expansion coefficient mismatch between the material of the first surface and the material of the third surface118, thereby providing a more stable structure of the formed MEMS pressure sensor and improving the reliability and the accuracy the formed MEMS pressure sensor. In addition, the processes for the first substrate100and the second substrate114are more flexible, the fabrication process of the formed MEMS pressure sensor is more compatible with various fabrication processes of integrated conductive layers, and the fabrication cost is reduced.

Reference is made toFIG. 7. The second base110(as shown inFIG. 6) is removed and a fifth surface122opposite to the third surface118of the second substrate is formed.

In the embodiment, since the protective layer111is located between the second base110and the pressure-sensing electrode113, a surface of the protective layer111is exposed after the second base110is removed. The protective layer111may be comprised of an insulating material, and can protect and isolate the pressure-sensing electrode113. The capacitance of the pressure-sensing electrode113changes due to a deformation of the pressure-sensing electrode113in a case that the protective layer111is applied with a pressure.

The second base110may be removed by a chemical mechanical polishing process or an etching process, and the etching process includes a dry etching process, a wet etching process or a combination of dry etching and wet etching. Since the second base110is removed from the fourth surface119of the second substrate114, a fifth surface122, i.e. the surface of the protective layer111, is formed on the side of the second substrate114opposite to the third surface118after the second base is removed.

Reference is made toFIG. 8. A first conductive plug123passing through the second substrate114from the fifth surface122of the second substrate114to the at least one conductive layer103is formed, and the first conductive plug123is used to electrically connect the conductive layer103to the pressure-sensing electrode113.

The first surface101of the first substrate100is in contact with the third surface118of the second substrate114, and no electrical connection exists on the contacting interface between the first surface101and the third surface118when at least one of the coupling layers is an insulator, hence the first conductive plug123needs to be formed. One end of the first conductive plug123is electrically connected to the conductive layer103and the other end of the first conductive plug123is exposed in the fifth surface122of the second substrate114. In this case, a first conductive structure may be directly formed partially on the fifth surface122and partially in the second substrate114, so that the first conductive structure is electrically connected to the first conductive plug123and the pressure-sensing electrode113, and thus the conductive layer103is electrically connected to the pressure-sensing electrode113.

Since no electrical connection layer has to be made between the first surface101and the third surface118, the first surface101is in contact with the third surface118in most regions other than a region of the cavity121, and a contact area between the first surface101and the third surface118is large. In this case, the mechanical strength of the stacked structure of the first substrate100and the second substrate114is higher after they are bonded, and it is difficult to bend or crack the stacked structure of the first substrate and the second substrate. In addition, no additional electrical connection layer is necessary between the first surface101and the third surface118, the first surface101and the third surface118may be comprised of material with similar thermal expansion coefficients. In this case, no excess stress or delamination is generated between the first substrate100due to a thermal expansion coefficient mismatch, after the first substrate100is bonded with the second substrate114. Therefore, the stacked structure of the first substrate100and the second substrate114has a more stable structure, a reduced size and a high adaptability of the fabrication process thereof.

The forming the first conductive plug123includes: forming a patterned layer on the fifth surface122of the second substrate114, with a region where the first conductive plug123is formed being exposed from the patterned layer; with the patterned layer as a mask, etching the protective layer111, the second coupling layer117and the first coupling layer106until the surface of the conductive layer103is exposed, to form a first through hole in the protective layer111, the second coupling layer117and the first coupling layer106; forming a conductive film partially on the fifth surface122and partially in the first through hole, with the first through hole being filled with the conductive film; and removing a portion of the conductive film on the fifth surface122until the fifth surface122is exposed. In an embodiment, the conductive film on the fifth surface may be removed completely. In another embodiment, a portion of the conductive film may be reserved on the fifth surface122.

An end of the first conducive plug123may protrude from, be recessed into or be flush with, the fifth surface122of the second substrate114.

In an embodiment, an insulating layer is formed on a surface of a sidewall of the first through hole before the conductive film is formed, and then the conductive film filling up the first through hole is formed after the insulating layer is formed.

The first conductive plug123may be comprised of copper, tungsten, aluminum, silver or gold. The conductive film may be formed by a physical vapor deposition process, a chemical vapor deposition process, an atomic layer deposition process, an electroplating process or a chemical plating process. The conductive film may be flattened by a chemical mechanical polishing process. In addition, a first barrier layer may be formed on the surface of the sidewall of the first through hole, the conductive film is formed on a surface of the first barrier layer, and the first barrier layer may be comprised of one or more of titanium, tantalum, titanium nitride and tantalum nitride.

In the embodiment, a third conductive plug124passing through from the fifth surface122of the second substrate114to the electrode interconnection layer is formed. A first conductive structure is subsequently formed with the third conductive plug124and a subsequently-formed first conductive layer. The first conductive structure is used to electrically connect the first conductive plug123to the pressure-sensing electrode113, and the pressure-sensing electrode113is electrically connected to the conductive layer103.

In the embodiment, a third through hole passing through the protective layer111is formed while the first through hole is formed. A surface of the electrode interconnection layer is exposed at the bottom of the third through hole. The conductive film is formed in the third through hole and fills up the third through hole, and then the third conductive plug124is formed in the third through hole.

In an embodiment, an insulating layer may be formed on a surface of a sidewall of the third through hole before the conductive film is formed, and then the conductive film filling up the third through hole is formed after the insulating layer is formed.

In another embodiment, the third conductive plug124may be formed before or after the first conductive plug123is formed.

Referring toFIG. 9, a first conductive structure, which is electrically connected to the first conductive plug123and the pressure-sensing electrode113, is formed.

In the embodiment, the first conductive structure includes the third conductive plug124and the first conductive layer125. The first conductive layer125is arranged on the fifth surface122of the second substrate114and is arranged on top surfaces of the first conductive plug123and the third conductive plug124. The third conductive plug124is electrically connected to the electrode interconnection layer, the first conductive plug123is electrically connected to the conductive layer103, and the first conductive layer125is electrically connected to the first conductive plug123and the third conductive plug124, and thus the pressure-sensing electrode113is electrically connected to the conductive layer103.

The first conductive layer125may be comprised of metal or metal compound, which includes one or more of copper, tungsten, aluminum, silver, titanium, tantalum, titanium nitride and tantalum nitride. The forming the first conductive layer125includes: depositing a conductive material layer on the fifth surface122of the second substrate114; forming a patterned layer on the conductive material layer with a portion of the surface of the conductive material layer being exposed from the patterned layer; etching the conductive material layer with the patterned layer being a mask until the fifth surface122is exposed. The conductive material layer may be formed by a chemical vapor deposition process, a physical vapor deposition process or an atomic layer deposition process. The patterned layer is a patterned photoresist layer. The conductive material layer may be etched by an anisotropic dry etching process.

The method for fabricating the MEMS pressure sensor according to the embodiment may be used to make devices suitable for multiple types of packaging, including Chip Scale Package (CSP), Quad Flat No-lead package (QFN), Dual flat no-lead package (DFN) or Small Outline Integrated Conductive layer package (SOIC).

Accordingly, the embodiment of the present disclosure further provides a MEMS pressure sensor formed according to the above method. Reference is still made toFIG. 9. The MEMS pressure sensor includes: a first substrate100and a second substrate114. The first substrate100includes a first surface101and a second surface102opposite to the first surface101. The first substrate100includes at least one conductive layer103arranged on the side of the first surface101of the first substrate100. The second substrate114includes a third surface118and a fifth surface122opposite to the third surface118, the second substrate114includes a pressure-sensing electrode113, and the second substrate114includes a pressure sensing region180in which the pressure-sensing electrode113is arranged. The first surface101of the first substrate100and the third surface118of the second substrate114are bonded with each other and a cavity121is formed between the first substrate100and the pressure sensing region180of the second substrate114. A first conductive plug123passing through the second substrate114from the fifth surface122of the second substrate114to the at least one conductive layer103is formed, to electrically connect the conductive layer103and the pressure-sensing electrode113.

In the following, the above structure is described in detail.

In the embodiment, the first substrate100further includes a fixed electrode140arranged on the side of the first surface101of the first substrate100. The fixed electrode140corresponds to the pressure-sensing electrode113. The cavity121is formed between the pressure-sensing electrode113and the fixed electrode140. In an embodiment, the first substrate100further includes a circuit.

In another embodiment, the second substrate further includes a fixed electrode corresponding to the pressure-sensing electrode, and a cavity is formed between the pressure-sensing electrode and the fixed electrode.

The second substrate114further includes a protective layer111arranged partially on a surface of the pressure-sensing electrode113and partially on a surface of the electrode interconnection layer, and a surface of the protection layer111is the fifth surface122. The protective layer111may be comprised of an insulating material such as silicon oxide, silicon nitride, silicon oxynitride, a low-k dielectric material or an ultra low-k dielectric material.

The first conductive structure includes a third conductive plug124and a first conductive layer125. The third conductive plug124passes through the second substrate114from the fifth surface122of the second substrate114to the electrode interconnection layer, and the first conductive layer125is arranged on the fifth surface122of the second substrate114and on top surfaces of the first conductive plug123and the third conductive plug124.

The second substrate114further includes a second coupling layer117arranged on the side of the third surface118; or the first substrate100includes a first coupling layer106arranged on the side of the first surface101; or the second substrate114further includes a second coupling layer117arranged on the side of the third surface118and the first substrate100includes a first coupling layer106arranged on the side of the first surface101. The first coupling layer106or the second coupling layer117may be comprised of one or more of an insulating material, a metal material, a metal compound material and a semiconductor material. In an embodiment, at least one of the first coupling layer106and the second coupling layer117is comprised of an insulating material.

In an embodiment, the first coupling layer106or the second coupling layer117is an adhesive bonding layer, which may be comprised of an insulating material, a semiconductor material, a metal material or an organic material. In another embodiment, the first coupling layer106is a bonding layer; or, the second coupling layer117is a bonding layer; or, the first coupling layer106and the second coupling layer117are bonding layers.

Second Embodiment

FIGS. 10 to 11are schematic cross-sectional diagram of a MEMS pressure sensor in a fabrication process according to an embodiment of the present disclosure.

Referring toFIG. 10, a first substrate200is prepared. The first substrate200includes a first surface201and a second surface202opposite to the first surface201. The first substrate200includes a self-test electrode230, and at least one conductive layer203arranged on the side of the first surface201of the first substrate200.

The first substrate200further includes a fixed electrode240arranged on the side of the first surface201of the first substrate200. When the first surface201of the first substrate200and a third surface of a second substrate are bonded with each other, the fixed electrode240corresponds to the pressure-sensing electrode and a cavity is formed between the pressure-sensing electrode and the fixed electrode240.

In addition, the first substrate200further includes a circuit including a semiconductor device structure and an electrical interconnection structure. The conductive layer203may be a conductive layer of the circuit, or, may be a conductive layer added to the circuit. The conductive layer may include a conductor or a semiconductor.

In the embodiment, the conductive layer203is formed on the first base204, and a first dielectric layer205is arranged between the conductive layer203and the first base204. The first substrate200may include a first coupling layer206arranged on the side of the first surface201. The first base204, the first dielectric layer205, the conductive layer203and the first coupling layer206are the same as those described in conjunction withFIG. 1according to the previous embodiment, which are not described herein.

A location of the self-test electrode230and a location of the fixed electrode240correspond to a location of a pressure sensing region of the second substrate. In the embodiment, the self-test electrode230is formed on a surface of the first dielectric layer. Since the location of the self-test electrode230and the location of the fixed electrode240correspond to the location of the pressure sensing region in the second substrate, that is, the self-test electrode230and the fixed electrode240are arranged corresponding to the pressure-sensing electrode after the first substrate200and the second substrate are bonded with each other.

In the embodiment, the self-test electrode230is located in the same layer as the conductive layer203. In another embodiment, the self-test electrode230may be higher or lower than the conductive layer203. In the embodiment, the self-test electrode230is located in the same layer as the fixed electrode240. In another embodiment, the self-test electrode230may be higher or lower than the fixed electrode240.

After the first substrate200and the second substrate are bonded, the self-test electrode230may generate an electrostatic pull on the pressure sensing region of the second substrate when a bias voltage is applied to the self-test electrode230, the pressure sensing region of the second substrate is a pressure sensing film and the pressure sensing film may be deformed due to the electrostatic pull. It is detected whether the pressure-sensing electrode works normally by detecting whether the electrostatic pull leads to a change in a capacitance of the capacitor including the pressure-sensing electrode.

The self-test electrode230may be comprised of a metal material, a metal compound material or a semiconductor material doped with ions. The forming the self-test electrode230includes: depositing an electrode material layer on a surface of the first dielectric layer205; forming a patterned layer on a surface of the electrode material layer, with a portion of the surface of the electrode material layer being exposed from the patterned layer; etching the electrode material layer with the patterned layer being a mask until the surface of the first dielectric layer205is exposed. The electrode material layer may be formed by a chemical vapor deposition process, a physical vapor deposition process or an atomic layer deposition process. The patterned layer is a patterned photoresist layer. The electrode material layer may be etched by an anisotropic dry etching process. In the embodiment, the self-test electrode230, the conductive layer203and the fixed electrode240are formed simultaneously. In another embodiment, the self-test electrode may be formed before or after the conductive layer203is formed, or may be formed before or after the fixed electrode is formed.

Reference is made toFIG. 11. A second substrate214is prepared. The second substrate214includes a third surface218and a fourth surface opposite to the third surface218. The second substrate214includes a second base and a pressure-sensing electrode213arranged on or above the second base. The second substrate214includes a pressure sensing region280in which the pressure-sensing electrode213is arranged. The pressure-sensing electrode is arranged on the side of the third surface218of the second substrate214. The first surface201of the first substrate200and the third surface218of the second substrate214are bonded with each other, and a cavity221is formed between the first substrate200and the pressure sensing region280of the second substrate214. The second base is removed to form a fifth surface222opposite to the third surface218of the second substrate214. A first conductive plug223passing through the second substrate214from the side of the fifth surface222of the second substrate214to the at least one conductive layer203is formed, and the first conductive plug223is used to electrically connect the conductive layer203to the pressure-sensing electrode213.

In the embodiment, after the first surface201of the first substrate200and the third surface218of the second substrate214are bonded with each other, the location of the self-test electrode230corresponds to the location of the pressure sensing region280. In this case, the self-test electrode230can apply an electrostatic pull to the pressure-sensing electrode213to detect whether the pressure-sensing electrode works normally.

In the embodiment, the second substrate214further includes a protective layer211and a first conductive structure. The first conductive structure includes a third conductive plug224and a first conductive layer225.

Steps of: preparing the second substrate214; bonding the first substrate200and the second substrate214with each other; removing the second base; forming the first conductive plug223and forming the first conductive structure are the same as those described in conjunction withFIGS. 2 to 9according to the previous embodiment, which are not described herein.

Accordingly, the embodiment of the present disclosure further provides a MEMS pressure sensor formed with the above method. Reference is still made toFIG. 11. The MEMS pressure sensor includes a first substrate200and a second substrate214. The first substrate200includes a first surface201and a second surface202opposite to the first surface201. The first substrate200includes a self-test electrode230, and at least one conductive layer203arranged on the side of the first surface201of the first substrate200. The second substrate214includes a third surface218and a fifth surface222opposite to the third surface218. The second substrate214includes a pressure-sensing electrode213. The second substrate214includes a pressure sensing region280in which the pressure-sensing electrode is arranged. The first surface201of the first substrate200and the third surface218of the second substrate214are bonded with each other and a cavity221is formed between the conductive layer203and the pressure-sensing electrode213. The location of the self-test electrode230corresponds to the location of the pressure sensing region280. A first conductive plug223passing through the second substrate214from the fifth surface222of the second substrate214to the at least one conductive layer203is formed, and the first conductive plug223is used to electrically connect the conductive layer203and the pressure-sensing electrode213.

In the embodiment, the first substrate200further includes a fixed electrode240arranged on the side of the first surface204of the first substrate200. When the first surface204of the first substrate200and the third surface218of the second substrate214are bonded with each other, the fixed electrode240corresponds to the pressure-sensing electrode213, and the cavity221is formed between the pressure-sensing electrode213and the fixed electrode240.

The first substrate200, the second substrate214, the pressure-sensing electrode213, the first conductive plug223and the first conductive structure are the same as those described in the previous embodiment, which are not described herein.

The self-test electrode230may be comprised of a metal material, a metal compound material or a semiconductor material doped with ions. The metal material includes one or more of copper, tungsten, aluminum, silver, titanium and tantalum. The metal compound material includes one or two of titanium nitride and tantalum nitride. The semiconductor material includes one or more of polycrystalline silicon, amorphous silicon, polycrystalline germanium, amorphous germanium, silicon germanium and silicon carbide which are doped with ions. The ions being doped include p-type ions, n-type ions, carbon ions, nitrogen ions, fluoride ions and hydrogen ions.

When a bias voltage is applied to the self-test electrode230, the self-test electrode230can generate an electrostatic pull on the pressure-sensing electrode213, and the pressure sensing film can be deformed due to the electrostatic pull. It may be detected whether the pressure-sensing electrode213works normally by detecting whether the electrostatic pull leads to a change in a capacitance of the capacitor including the pressure-sensing electrode213.

Third Embodiment

FIGS. 12 to 15are schematic cross-sectional diagrams of a MEMS pressure sensor in a fabrication process according to an embodiment of the present disclosure.

Referring toFIG. 12, a second substrate314is prepared. The second substrate314includes a third surface318and a fourth surface319opposite to the third surface318. The second substrate314includes a second base310and a pressure-sensing electrode313arranged on or above the second base310. The second substrate314includes a pressure sensing region380and a reference unit region331. The pressure-sensing electrode313is arranged on the side of the third surface318of the second substrate314and is arranged in the pressure sensing region380.

A pressure-sensing electrode313is further formed in the reference unit region331.

In the embodiment, the second substrate314further includes a second coupling layer317arranged on the side of the third surface318of the second substrate314, and the second coupling layer317includes first openings320. The first openings320are formed in the pressure sensing region380and the reference unit region331. The first openings320are used to form cavities in the pressure sensing region380and the reference unit region331after the first substrate and the second substrate314are bonded.

The second substrate314and the pressure-sensing electrode313are the same as those described in conjunction withFIGS. 2 to 5according to the previous embodiment, which are not described herein.

Referring toFIG. 13, a first substrate300is prepared. The first substrate300includes a first surface301and a second surface302opposite to the first surface301. The first substrate300includes at least one conductive layer303arranged on the side of the first surface301of the first substrate300. The first surface301of the first substrate300and the third surface318of the second substrate314are bonded with each other. A cavity321is formed between the first substrate300and the pressure sensing region380of the second substrate314, and a cavity321is formed between the first substrate300and the reference unit region331of the second substrate314. A deformation on a portion of the second substrate314corresponding to the reference unit region331is less than a deformation on a portion of the second substrate314corresponding to the pressure sensing region380, under a same external pressure.

In the embodiment, the first substrate300further includes a fixed electrode340arranged on the side of the first surface301of the first substrate300. When the first surface301of the first substrate300and the third surface318of the second substrate314are bonded with each other, the fixed electrode340corresponds to the pressure-sensing electrode313and the cavity321is formed between the pressure-sensing electrode313and the fixed electrode340.

A first base304is the same as that described in conjunction withFIG. 1according to the previous embodiment, which is not described herein. A step of bonding the first surface301of the first substrate300and the third surface318of the second substrate314with each other is the same as the step described in conjunction withFIG. 6according to the previous embodiment, which is not described herein.

The pressure sensing region380of the second substrate314and the reference unit region331of the second substrate314each include the first opening in the second coupling layer317. In this case, the cavities321may be formed in the pressure sensing region380and the reference unit region with the first openings and the first surface301of the first substrate300.

Since a cover layer is formed in a later step on a portion of the fifth surface of the second substrate314corresponding to the reference unit region331, a change in a capacitance of a capacitor including the pressure-sensing electrode313in the reference unit region331due to an external pressure can be avoided or reduced, and the capacitance of the pressure-sensing electrode313in the reference unit region331may change due to factors other than pressure. An electrical signal generated due to the external pressure can be obtained by subtracting an electrical signal output from the pressure-sensing electrode313in the reference unit region331from an electrical signal output from the pressure-sensing electrode313in the pressure sensing region380. Therefore, the accuracy of the formed MEMS pressure sensor is improved.

Referring toFIG. 14, the second base310(shown inFIG. 13) is removed to form a fifth surface322opposite to the third surface318of the second substrate314. A first conductive plug323passing through the second substrate314from the fifth surface122of the second substrate314to the at least one conductive layer303is formed. The first conductive plug323is used to electrically connect the conductive layer303to the pressure-sensing electrode313.

In the embodiment, a first conductive structure includes a third conductive plug324and a first conductive layer325.

A step of removing the second base310is the same as the step described in the previous embodiment, which is not described herein. Steps of forming the first conductive plug323and the first conductive structure are the same as steps described in the previous embodiment, which are not described herein.

Referring toFIG. 15, a cover layer332is formed on a portion of the fifth surface322of the second substrate314corresponding to the reference unit region331, after the second base310(as shown inFIG. 13) is removed.

The cover layer331is comprised of an insulating material. The cover layer332can protect the pressure-sensing electrode313in the reference unit region331from being affected by an external force since the cover layer331has a high stiffness.

The forming the cover layer332includes: depositing a cover film partially on the fifth surface322and partially on a surface of the first conductive structure; forming a patterned layer on a surface of the cover film; and etching the cover film with the patterned layer being a mask until a portion of the fifth surface322located in the pressure sensing region380is exposed. The cover layer232may be comprised of one or more of silicon oxide, silicon nitride, silicon oxynitride, amorphous carbon, polycrystalline silicon, amorphous silicon, polycrystalline germanium and amorphous germanium. The cover film may be formed by a chemical vapor deposition process, a physical vapor deposition process or an atomic layer deposition process. The cover film may be etched by an anisotropic dry etching process.

Since the cover layer332is formed on a portion of the fifth surface322of the second substrate314corresponding to the reference unit region331, the capacitance of the pressure-sensing electrode313in the reference unit region331may show less or no change in response to an external pressure, but it may change due to factors other than pressure. An electrical signal generated due to the external pressure can be obtained by subtracting the electrical signal output by the pressure-sensing electrode313in the reference unit region331from the electrical signal output by the pressure-sensing electrode313in the pressure sensing region380.

Accordingly, the embodiment of the present disclosure further provides a MEMS pressure sensor formed with the above method. Reference is still made toFIG. 15, the MEMS pressure sensor includes a first substrate300and the second substrate314. The first substrate300includes a first surface301and a second surface302opposite to the first surface301. The first substrate300includes at least one conductive layer30arranged on the side of the first surface301of the first substrate300. The second substrate314includes a third surface318and a fifth surface322opposite to the third surface318. The second substrate314includes a pressure-sensing electrode313. The second substrate314includes a pressure sensing region380and a reference unit region331. The pressure-sensing electrodes313are arranged in the pressure sensing region380and the reference unit region331. The first surface301of the first substrate300and the third surface318of the second substrate314are bonded with each other. A cavity321is formed between the first substrate300and the pressure sensing region380of the second substrate314, and a cavity321is formed between the first substrate300and the reference unit region331of the second substrate314. A first conductive plug323passing through the second substrate314from the fifth surface322of the second substrate314to the at least one conductive layer303is formed, and a first conductive structure electrically connected to the first conductive plug323and the pressure-sensing electrodes313is formed. The first conductive plug323is used to electrically connect the conductive layer303to the pressure-sensing electrode313.

In the embodiment, the first substrate300further includes a fixed electrode340arranged on the side of the first surface301of the first substrate300. The fixed electrode340corresponds to the pressure-sensing electrode313and the cavity321is formed between the pressure-sensing electrode313and the fixed electrode340.

The cover layer332may be comprised of one or more of silicon oxide, silicon nitride, silicon oxynitride, amorphous carbon, polycrystalline silicon, amorphous silicon, polycrystalline germanium and amorphous germanium.

The first substrate300, the second substrate314, the pressure-sensing electrode313, the fixed electrode340, the conductive layer303, the first conductive plug323and the first conductive structure are the same as those described in conjunction withFIG. 9according to the previous embodiment, which are not described herein.

Fourth Embodiment

FIGS. 16 to 17are schematic cross-sectional diagram of a MEMS pressure sensor in a fabrication process according to an embodiment of the present disclosure.

Referring toFIG. 16, a first substrate400is prepared. The first substrate400includes a first surface401and a second surface402opposite to the first surface401. The first substrate400includes a first base404, and at least one conductive layer403arranged on the side of the first surface401of the first substrate400. A second opening450in the first substrate400is formed.

In the embodiment, the first substrate400further includes a fixed electrode440arranged on the side of first surface401of the first substrate400.

The forming the second opening450includes: forming a patterned layer on the second surface402of the first substrate400, with a location where the second opening is to be formed being exposed from the patterned layer; etching the first substrate400with the patterned layer being a mask until the first substrate400is passed through, to form a second opening450. The patterned layer is a patterned photoresist layer, and the etching process includes an anisotropic dry etching process.

The first substrate400, and the first base404and the conductive layer403of the first substrate400are the same as those described in conjunction withFIG. 1according to the previous embodiment, which are not described herein.

Referring toFIG. 17, a second substrate414is prepared. The second substrate414includes a third surface418and a fourth surface opposite to the third surface418. The second substrate414includes a second base and a pressure-sensing electrode413arranged on or above the second base. The second substrate414includes a pressure sensing region480in which the pressure-sensing electrode413is arranged. The pressure-sensing electrode413is arranged on the side of the third surface418of the second substrate414. The first surface401of the first substrate400and the third surface418of the second substrate414are bonded with each other, and a cavity421between the first substrate400and the pressure sensing region480of the second substrate414. The second base is removed to form a fifth surface422opposite to the third surface418of the second substrate414. A first conductive plug423passing through the second substrate414from the side of the fifth surface422of the second substrate414to the at least one conductive layer403is formed, and the first conductive plug423is used to electrically connect the conductive layer403to the pressure-sensing electrode418.

When the first surface401of the first substrate400and the third surface418of the second substrate414are bonded with each other, the fixed electrode440corresponds to the pressure-sensing electrode413, and the cavity is formed between the pressure-sensing electrode413and the fixed electrode440.

In the embodiment, a first conductive structure electrically connected to the first conductive plug423and the pressure-sensing electrode413is formed. The first conductive structure includes a third conductive plug424and a first conductive layer425.

Material, structures and fabrication steps and fabrication processes of the second substrate414are the same as those described in conjunction withFIGS. 2 to 5according to the previous embodiment; a step of bonding the first substrate400and the second substrate414with each other is the same as that described in conjunction withFIG. 6according to the previous embodiment; a step of removing the second base is the same as that described in conjunction withFIG. 7according to the previous embodiment; and steps of forming the first conductive plug423and the first conductive structure are the same as those described in the previous embodiment; which are not described herein.

After the first surface401of the first substrate400and the third surface418of the second substrate414are bonded with each other, a location of the second opening450corresponds to a location of the pressure sensing region480of the second substrate. Therefore, the second opening450is in communication with the cavity421, and two sides of the pressure sensing film are exposed to the external environment.

Since the second opening450is exposed to the external environment, pressures from the external environment are obtained on both sides of the pressure sensing film. In a case that the pressures on the two sides of the pressure sensing film are different, the pressure sensing film is deformed and a capacitance of the pressure-sensing electrode413changes. Therefore, the pressure-sensing electrode413according to the embodiment can acquire a differential pressure signal for the two sides, and the formed MEMS pressure sensor may serve as a differential pressure sensor.

Accordingly, the embodiment of the present disclosure further provides a MEMS pressure sensor formed with the above method. Reference is still made toFIG. 17. The MEMS pressure sensor includes a first substrate400and a second substrate414. The first substrate400includes a first surface401and a second surface402opposite to the first surface401. The first substrate400includes at least one conductive layer403arranged on the side of the first surface401of the first substrate400. The second substrate414includes a third surface418and a fifth surface422opposite to the third surface418. The second substrate414includes a pressure-sensing electrode413. The second substrate414includes a pressure sensing region480in which the pressure-sensing electrode is arranged. The first surface401of the first substrate400and the third surface418of the second substrate414are bonded with each other and a cavity421is formed between the first substrate400and the pressure sensing region480of the second substrate414. A first conductive plug423passing through the second substrate414from the fifth surface422of the second substrate414to a surface of the at least one conductive layer403is formed, and the first conductive plug423is used to electrically connect the conductive layer403to the pressure-sensing electrode413.

In the embodiment, the first substrate400further includes a fixed electrode440arranged on the side of the first surface404of the first substrate400. The fixed electrode440corresponds to the pressure-sensing electrode413and the cavity421is formed between the pressure-sensing electrode413and the fixed electrode440.

In the embodiment, the MEMS pressure sensor further includes a first conductive structure electrically connected to the first conductive plug423and the pressure-sensing electrode413, and a second opening450passing through the first substrate400. A location of the second opening450corresponds to a location of the pressure sensing region480of the second substrate414.

Fifth Embodiment

FIGS. 18 to 20are schematic cross-sectional diagrams of a MEMS pressure sensor in a fabrication process according to an embodiment of the present disclosure.

Referring toFIG. 18, a first substrate500and a second substrate514are prepared. The first substrate500includes a first surface501and a second surface502opposite to the first surface501. The first substrate500includes at least one conductive layer503arranged on the side of the first surface501of the first substrate500. The second substrate514includes a third surface518and a fourth surface519opposite to the third surface518. The second substrate514includes a second base510and a pressure-sensing electrode513arranged on or above the second base510. The second substrate514includes a pressure sensing region580in which the pressure-sensing electrode513is arranged. The pressure-sensing electrode is arranged on the side of the third surface518of the second substrate514. The first surface501of the first substrate500and the third surface518of the second substrate514are bonded with each other and a cavity521is formed between the first substrate500and the pressure sensing region580of the second substrate514.

In the embodiment, the first substrate500further includes a fixed electrode540arranged on the side of the first surface501of the first substrate500. When the first surface501of the first substrate500and the third surface518of the second substrate514are bonded with each other, the fixed electrode540corresponds to the pressure-sensing electrode513and the cavity521is formed between the pressure-sensing electrode513and the fixed electrode514.

In another embodiment, the second substrate further includes a fixed electrode corresponding to the pressure-sensing electrode, and the cavity is formed between the pressure-sensing electrode and the fixed electrode.

In the embodiment, the first substrate500includes a first coupling layer506arranged on the side of the first surface501.

In an embodiment, the first substrate500further includes a self-test electrode. A location of the self-test electrode corresponds to a location of the pressure sensing region580of the second substrate514after the first surface501of the first substrate500and the third surface518of the second substrate514are bonded with each other.

The second substrate514further includes a protective layer511arranged on a surface of the second base510, and the pressure-sensing electrode513is arranged on a surface of the protective layer511. In an embodiment, the forming the second substrate514includes: preparing a semiconductor-on-insulator substrate, which includes a base, a insulating layer arranged on a surface of the base and a semiconductor layer arranged on a surface of the insulating layer; forming a first patterned layer on a surface of the semiconductor layer, with a portion of the surface of the semiconductor layer be exposed from the first patterned layer; etching the semiconductor layer with the first patterned layer being a mask to form a pressure-sensing electrode513, where the base is the second base510and the insulating layer is the protective layer511; and removing the first patterned layer after the semiconductor layer is etched. An electrode interconnection layer may be formed by etching the semiconductor layer, and the electrode interconnection layer is electrically connected to the pressure-sensing electrode513. In another embodiment, the second base510may be a body base.

The second substrate514further includes a second coupling layer517arranged on the side of the third surface518. In an embodiment, at least one of the first coupling layer506and the second coupling layer517may be comprised of an insulating material.

In an embodiment, the first surface501of the first substrate500and the third surface518of the second substrate514are bonded with each other by a direct-bonding process. In another embodiment, the first surface501of the first substrate500and the third surface518of the second substrate514are bonded with each other by an adhesive bonding process. The first coupling layer506or the second coupling layer517is an adhesive bonding layer which may be comprised of an insulating material, a semiconductor material, a metal material or an organic material.

In an embodiment, the second substrate514further includes a sensing unit region and a reference unit region, and the cavities521are formed in the sensing unit region and the reference unit region.

In an embodiment, the forming the cavity521includes: forming a first opening from the third surface518of the second substrate514before the first surface501of the first substrate500and the third surface518of the second substrate514are bonded with each other, with a location of the first opening corresponding to a location of the pressure sensing region580of the second substrate514; and forming a cavity521with the first opening and the first surface501of the first substrate500after the first surface501of the first substrate500and the third surface518of the second substrate514are bonded with each other.

In an embodiment, a second opening passing through the first substrate500is formed. A location of the second opening corresponds to a location of the pressure sensing region580of the second substrate514after the first surface501of the first substrate500and the third surface518of the second substrate514are bonded with each other.

In the embodiment, the first substrate500, the second substrate514and a step of bonding the first substrate500and the second substrate514with each other are the same as those described in conjunction withFIGS. 1 to 6according to the previous embodiments, which are not described herein.

Referring toFIG. 19, the second substrate514is thinned from the fourth surface519(shown inFIG. 18) by partially removing the second base510, to form a fifth surface522opposite to the third surface518of the second substrate514.

The second base510may be thinned from the fourth surface519by a chemical mechanical polishing process. In the embodiment, the fourth surface519of the second substrate514is a surface of the second base510, and hence the second base510is thinned by the chemical mechanical polishing process. The pressure-sensing electrode513and the protective layer511are protected by a portion of the second base510not being thinned and located on a surface of the protective layer511, after the second base510is thinned.

In an embodiment, the second substrate514further includes a sensing unit region and a reference unit region, cavities521are formed in the sensing unit region and the reference unit region, and a cover layer is formed on a portion of the fifth surface522of the second substrate514corresponding to the reference unit region after the second base510is thinned.

Referring toFIG. 20, a first conductive plug523passing through the second substrate514from the side of the fifth surface522of the second substrate514to the at least one conductive layer503is formed, and the first conductive plug523is used to electrically connect the conductive layer503to the pressure-sensing electrode513.

The first conductive plug523electrically connects the conductive layer503to the pressure-sensing electrode513via a first conductive structure. The first conductive structure includes a third conductive plug524passing through the second substrate514from the fifth surface522of the second substrate514to an electrode interconnection layer, and a first conductive layer525arranged partially on the fifth surface522of the second substrate and partially on top surfaces of the first conductive plug523and the third conductive plug524. An insulating layer may further be formed between the first conductive layer525and the second base510.

Material, structures and fabrication steps of the first conductive structure and the first conductive plug523are the same as those described in conjunction withFIGS. 8 and 9according to the previous embodiment, which are not described herein.

Accordingly, the embodiment of the present disclosure further provides a MEMS pressure sensor formed with the above method. Reference is still made toFIG. 20. The MEMS pressure sensor includes a first substrate500and a second substrate514. The first substrate500includes a first surface501and a second surface502opposite to the first surface501. The first substrate500includes at least one conductive layer503close to the first surface501of the first substrate500. The second substrate514includes a third surface518and a fifth surface522opposite to the third surface518. The second substrate514includes a second base510and a pressure-sensing electrode513arranged on or above the second base510. The second substrate514includes a pressure sensing region580in which the pressure-sensing electrode513is arranged. The pressure-sensing electrode513is arranged on the side of the third surface518of the second substrate514. The first surface501of the first substrate500and the third surface518of the second substrate514are bonded with each other, and a cavity521is formed between the first substrate500and the pressure sensing region580of the second substrate514. A first conductive plug523passing through the second substrate514from the side of the fifth surface522of the second substrate514to the at least one conductive layer503is formed, and the first conductive plug523is used to electrically connect the conductive layer503to the pressure-sensing electrode513.

In the following, the above structure is described in detail.

In the embodiment, the first substrate500further includes a fixed electrode540arranged on the side of the first surface501of the first substrate500, the fixed electrode540corresponds to the pressure-sensing electrode513, and the cavity521is formed between the pressure-sensing electrode513and the fixed electrode540.

In another embodiment, the second substrate further includes a fixed electrode corresponding to the pressure-sensing electrode, and the cavity is formed between the pressure-sensing electrode and the fixed electrode.

The second substrate514further includes a protective layer511arranged on a surface of the pressure-sensing electrode513, and a surface of the protective layer511is the fifth surface522.

The first conductive plug523is electrically connected to the conductive layer503and the pressure-sensing electrode513via a first conductive structure. The first conductive structure includes a third conductive plug524passing through the second substrate514from the fifth surface522of the second substrate514to the electrode interconnection layer, and a first conductive layer525arranged on the fifth surface522of the second substrate514. The first conductive layer is also arranged on top surfaces of the first conductive plug523and the third conductive plug524.

The second substrate514further includes a second coupling layer517arranged on the side of the third surface518. Alternatively, the first substrate500includes a first coupling layer506arranged on the side of the first surface501. Alternatively, the second substrate514further includes a second coupling layer517arranged on the side of the third surface518and the first substrate500includes a first coupling layer506arranged on the side of the first surface501.

In an embodiment, at least one of the first coupling layer506and the second coupling layer517may be comprised of an insulating material.

In an embodiment, the first substrate500further includes a circuit.

In an embodiment, the first coupling layer506or the second coupling layer507is an adhesive bonding layer which may be comprised of an insulating material, a semiconductor material, a metal material or an organic material.

In another embodiment, the first coupling layer506is a bonding layer; or the second coupling layer517is a bonding layer; or the first coupling layer506and the second coupling layer517are bonding layers.

Sixth Embodiment

FIGS. 21 to 23are schematic cross-sectional diagrams of a MEMS pressure sensor in a fabrication process according to an embodiment of the present disclosure.

Referring toFIG. 21, a first substrate600and a second substrate614are prepared. The first substrate600includes a first surface601and a second surface602opposite to the first surface601. The first substrate600includes a first base604, and at least one conductive layer603arranged on the side of the first surface601of the first substrate600. The second substrate614includes a third surface618and a fourth surface opposite to the third surface618. The second substrate614includes a second base610and a pressure-sensing electrode613arranged on or above the second base610. The second substrate614includes a pressure sensing region680in which the pressure-sensing electrode613is arranged. The pressure-sensing electrode613is arranged on the side of the third surface618of the second substrate614. The first surface601of the first substrate600and the third surface618of the second substrate614are bonded with each other and a cavity621is formed between the first substrate600and the pressure sensing region680of the second substrate614. The second substrate614is thinned from the fourth surface by partially removing the second base610, to form a fifth surface622opposite to the third surface618of the second substrate614.

In the embodiment, the first substrate600further includes a fixed electrode640arranged on the side of the first surface601of the first substrate600. When the first surface601of the first substrate600and the third surface618of the second substrate614are bonded with each other, the fixed electrode640corresponds to the pressure-sensing electrode513and the cavity is formed between the pressure-sensing electrode613and the fixed electrode640.

In another embodiment, the second substrate further includes a fixed electrode corresponding to the pressure-sensing electrode, and the cavity is formed between the pressure-sensing electrode and the fixed electrode.

The second substrate614further includes a second coupling layer617on the side of the third surface618. A step of bonding the first surface601of the first substrate600and the third surface618of the second substrate614with each other and a step of thinning the second substrate614from the fourth surface are the same as those described in conjunction withFIGS. 18 and 19according to the previous embodiment, which are not described herein.

Referring toFIG. 22, a third opening660is formed in the second substrate614after the second substrate614is thinned from the fourth surface, and a location of the third opening660corresponds to a location of the pressure sensing region680of the second substrate614.

The second opening660may pass through the second base610, or may not pass through the second base610.

In an embodiment, a third opening formed in the second substrate does not pass through the second base. Alternatively, at least one fifth through hole passing through the second base is formed on the side of the fifth surface of the second substrate, and a location of the fifth through hole corresponds to the pressure sensing region.

The second base having the fifth through hole may filter out dust in the air and may be used for an electric shielding. In addition, the second base located in the pressure sensing region may serve as a self-test electrode. In a case that a bias voltage is applied to the second base, the second base may generate an electrostatic pull on the pressure-sensing electrode to detect whether the pressure-sensing resistor works normally.

The forming the third opening660includes: forming a patterned layer on the fifth surface622of the second substrate614, with a location where a third opening660is to be formed being exposed from the patterned layer; and etching the fifth surface622of the second substrate614with the patterned layer being a mask, to form a third opening660. The patterned layer is a patterned photoresist layer. The etching process includes an anisotropic dry etching process. In the embodiment, the protective layer611is exposed through the third opening660.

Since a region other than the pressure sensing region680is covered by the second base610, a distance from the pressure-sensing electrode613to the external environment is lengthened without affecting an accuracy of detecting an external pressure by the pressure-sensing electrode613. In this case, the pressure-sensing electrode613is protected, and a pressure sensing film and a protective layer611on the surface of the pressure sensing film is prevented from wears or other damages.

In an embodiment, the second substrate614further includes a sensing unit region and a reference unit region, and the cavity621is formed in the sensing unit and the reference unit region. In this case, only a portion of a surface of the protective layer611corresponding to the sensing unit region is exposed through the third opening, and a portion of the surface region of the protective layer611corresponding to the reference unit region is still covered by the second base610. Therefore, no additional cover layer is necessary on or above the second base610for increasing the stiffness, and the second base610may serve as a cover layer on a surface of a pressure sensing region612located in the reference unit region.

Referring toFIG. 23, a first conductive plug623passing through the second substrate614from the side of the fifth surface622of the second substrate614to a surface of the at least one conductive layer603is formed, and the first conductive plug623is used to electrically connect the conductive layer603to the pressure-sensing electrode613.

Material, structures and forming steps of a first conductive structure and the first conductive plug623are the same as those described in conjunction withFIGS. 8 and 9according to the previous embodiment, which are not described herein.

Accordingly, the embodiment of the present disclosure further provides a MEMS pressure sensor formed with the above method. Reference is still made toFIG. 23. The MEMS pressure sensor includes a first substrate600and a second substrate614. The first substrate600includes a first surface601and a second surface602opposite to the first surface601. The first substrate600includes a circuit603close to the first surface601of the first substrate600. The second substrate614includes a third surface618and a fifth surface622opposite to the third surface618. The second substrate614includes a second base610and a pressure-sensing electrode613arranged on or above the second base610, and the pressure-sensing electrode613is arranged on the side of the third surface618of the second substrate614. The second substrate614includes a third opening660, and a location of the third opening660corresponds to a location of the pressure-sensing electrode613. The first surface601of the first substrate600and the third surface618of the second substrate614are bonded with each other, and a cavity621is formed between the first substrate600and the second substrate614. A first conductive plug623passing through the second substrate614from the fifth surface622of the second substrate614to the surface of the circuit603is formed. A first conductive structure, which is electrically connected to the pressure-sensing electrode613and the first conductive plug623, is formed.

Seventh Embodiment

FIGS. 24 to 26are schematic cross-sectional diagrams of a MEMS pressure sensor in a fabrication process according to an embodiment of the present disclosure.

Referring toFIG. 24, a second substrate714is prepared. The second substrate714includes a third surface718and a fourth surface719opposite to the third surface718. The second substrate714includes a second base710and a pressure-sensing electrode713arranged in the second base710. The second substrate714includes a pressure sensing region780in which the pressure-sensing electrode713is arranged. The pressure-sensing electrode is arranged on the side of the third surface718of the second substrate714.

In the embodiment, the pressure-sensing electrode is formed by the second base710which is a body base. A second coupling layer717is arranged on a surface of the second base710. The pressure-sensing electrode is formed on a side of the second base710in the pressure sensing region780close to the third surface718. Material, structures and fabrication processes of the second coupling layer717are the same as those described in the previous embodiments, which are not described herein.

In the embodiment, a first opening720is formed on the side of the third surface718of the second substrate714, and a location of the first opening720corresponds to a location of the pressure sensing region780.

In an embodiment, the second substrate714further includes a sensing unit region and a reference unit region, and the pressure-sensing electrode is formed in the sensing unit and the reference unit region.

Referring toFIG. 25, a first substrate700is prepared. The first substrate700includes a first surface701and a second surface702opposite to the first surface701. The first substrate701includes at least one conductive layer703arranged on the side of the first surface701of the first substrate700. The first surface701of the first substrate700and the third surface718of the second substrate714are bonded with each other, and a cavity721is formed between the first substrate700and the pressure sensing region780of the second substrate714. The second substrate714is thinned from the fourth surface719of the second substrate714by partially removing the second base710, to form the fifth surface722opposite to the third surface718of the second substrate714.

In the embodiment, the first substrate700is the same as those described according to the previous embodiment; a step of bonding the first substrate700and the second substrate714, and a step of thinning the second substrate714from the fourth surface719are the same as those described in conjunction withFIGS. 18 and 19according to the previous embodiment, which are not described herein.

The first substrate700further includes a circuit including a semiconductor component structure and an electrical interconnection structure. The conductive layer703may be a conductive layer of the circuit, or may be a conductive layer added to the circuit. The conductive layer703may include a conductor or a semiconductor.

In the embodiment, the first substrate700further includes a fixed electrode740arranged on the side of the first surface701of the first substrate700, and a location of the first substrate700corresponds to a location of the pressure sensing region780of the second substrate714.

In the embodiment, the first substrate700includes a first coupling layer706on the side of the first surface701. In an embodiment, at least one of the first coupling layer706and the second coupling layer717may be comprised of an insulating material.

In an embodiment, the first surface701of the first substrate700and the third surface718of the second substrate714may be bonded with each other by a direct-bonding process. In another embodiment, the first surface701of the first substrate700and the third surface718of the second substrate714may be bonded with each other by an adhesive bonding process. The first coupling layer706or the second coupling layer717is an adhesive bonding layer, which may be comprised of an insulating material, a semiconductor material, a metal material or an organic material.

In the embodiment, when the first substrate700and the second substrate714are bonded with each other, a cavity721may be formed with the first substrate700and the first opening720located on the side of the third surface718of the second substrate714, and the cavity721is arranged between the pressure-sensing electrode713and the fixed electrode740.

Referring toFIG. 26, after the second substrate714is thinned from the fourth surface719of the second substrate714, the second base710(as shown inFIG. 25) is etched to form a pressure-sensing electrode713. A first conductive plug723passing through the second substrate714from the side of the fifth surface722of the second substrate714to the at least one conductive layer703is formed, and the first conductive plug723is used to electrically connect the conductive layer703to the pressure-sensing electrode713.

A location of the pressure-sensing electrode713corresponds to a location of the pressure sensing region780. In the embodiment, an electrode interconnection layer is formed by etching the second base710while the pressure-sensing electrode713is formed. The electrode interconnection layer is electrically connected to the pressure-sensing electrode713.

In the embodiment, after the cavity721is formed, a third dielectric layer726is formed partially on a surface of the second coupling layer717and partially on a surface of the pressure-sensing electrode713. The first conductive plug723passes through the third dielectric layer, the second coupling layer717and the first coupling layer706until it is connected to the at least one conductive layer703.

In the embodiment, a third conductive plug724is formed in the third dielectric layer726and is electrically connected to the electrode interconnection layer. A first conductive layer725is formed partially on a surface of the third dielectric layer726, partially on a surface of the third conductive plug724and partially on a surface of the first conductive plug723. A first conductive structure is formed with the third conductive plug724and the first conductive layer725. The first conductive plug723is electrically connected to the pressure-sensing electrode713through the first conductive structure.

Material, structures and forming steps of the first conductive structure and the first conductive plug723are the same as those described in conjunction withFIGS. 8 and 9according to the previous embodiment, which are not described herein.

Eighth Embodiment

Based onFIG. 9,FIG. 27is a schematic cross-sectional diagram of a MEMS pressure sensor in a fabrication process according to an embodiment of the present disclosure.

Referring toFIG. 27, a fourth conductive plug800passing through the first substrate100from the side of the second surface102of the first substrate100to the at least one conductive layer103is formed. The conductive layer103connected to the fourth conductive plug800and the conductive layer103connected to the first conductive plug123may be arranged in a same layer or different layers.

In the embodiment, the forming the fourth conductive plug800includes: forming a fourth dielectric layer801on the second surface of the first substrate100, with a portion of the second surface102of the first substrate100being exposed from the fourth dielectric layer801; etching the first substrate100with the fourth dielectric layer801being a mask until at least one conductive layer103is exposed, to form a fourth through hole in the first substrate100; and forming a fourth conductive plug800in the fourth through hole.

In the embodiment, before the fourth dielectric layer801is formed, the first substrate100may be thinned from the second surface102, thereby reducing an etching depth and the difficulty of an etching process for forming the fourth through hole.

In the embodiment, after the fourth conductive plug800is formed, the method further includes: forming a fourth conductive layer802on a surface of the fourth dielectric layer, with the fourth conductive layer802being located on a top surface of the fourth conductive plug800. In addition, a solder ball803may be formed on a surface of the fourth conductive layer802, and the formed MEMS pressure sensor may be electrically connected to wires on a printed circuit board via the solder ball803.

The fourth dielectric layer801is used to electrically isolate the fourth conductive layer802from the first substrate104. The fourth dielectric layer801may be comprised of silicon oxide, silicon nitride, silicon oxynitride, a low-k dielectric material or an ultra low-k dielectric material. The fourth conductive layer802may be comprised of a conductive material including a metal material, a metal compound material or a semiconductor material doped with ions. The fourth through hole may be formed by an anisotropic dry etching process. The first substrate100may be thinned from the second surface102by a chemical mechanical polishing process.

The forming the fourth conductive plug800includes: forming a conductive film partially on the second surface102and partially in the fourth through hole, with the fourth through hole being filled with the conductive film; and removing an unnecessary portion of the conductive film on the second surface102to form the fourth conductive plug800. In an embodiment, the conductive film on the second surface102may be removed completely. In another embodiment, a portion of the conductive film may be reserved on the second surface102.

An end of the fourth conductive plug800may protrude from, be recessed into or be flush with, the second surface102.

In an embodiment, before the conductive film is formed, an insulating layer is formed on a surface of a sidewall of the fourth through hole, and then the conductive film filling up the fourth through hole is formed after the insulating layer is formed. The insulating layer is used to electrically isolate the conductive film from the first base104.

The fourth conductive plug800may be comprised of copper, tungsten, aluminum, silver or gold. The conductive film may be formed by a physical vapor deposition process, a chemical vapor deposition process, an atomic layer deposition process, an electroplating process or a chemical plating process. The conductive film on the second surface102may be removed by a chemical mechanical polishing process. In addition, a first barrier layer may be formed on the surface of the wall side of the fourth through hole and the conductive film is formed on a surface of the first barrier layer. The first barrier layer may be comprised of one or more of titanium, tantalum, titanium nitride and titanium nitride.

In another embodiment, before the first substrate and the second substrate are bonded with each other, a fourth conductive plug is formed from the side of the first surface101of the first substrate100, that is, the fourth conductive plug may pass through the first substrate100, or may not pass through the first substrate100. In a case that the fourth conductive plug does not pass through the first substrate100, after the fourth conductive plug is formed, the first substrate100is thinned from the second surface102until the fourth conductive plug is exposed. In the embodiment, the formed fourth conductive plug passes from the second surface102of the first substrate100to the at least one conductive layer103on the side of the first surface101. The forming the fourth conductive plug800includes: forming a fourth through hole on the side of the first surface101of the first substrate100, with the bottom of the fourth through hole protrudes into the first base104; forming a conductive film partially on the first surface101and partially in the fourth through hole, with the fourth through hole being filled with the conductive film; and removing an unnecessary portion of the conductive film on the first surface101to form the fourth conductive plug. In an embodiment, an insulating layer is formed on the surface of a sidewall of the fourth through hole before the conductive film is formed before the conductive film is formed, and then the conductive film filling up the fourth through hole is formed after the insulating layer is formed. The insulating layer is used to electrically isolate the conductive film from and the first base104.

Although the present disclosure is disclosed above, it is not intended to limit the present disclosure. Various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the present disclosure. Therefore, the scope of the present disclosure should be defined by the appended claims.