Patent Description:
It is known how the electrical performances of a MEMS device may degrade over time, if the so-called cap, which is part of the corresponding package, is not properly grounded. In fact, in the event that the cap is floating, undesired electric discharges may occur, which may damage the MEMS device. Furthermore, the presence of a floating cap may cause a reduction of the performances of MEMS devices such as, for example, MEMS inertial sensors, due to the onset of undesired electrostatic forces acting on the relative movable masses.

For these reasons, solutions are known which provide for protecting MEMS devices, and ASIC circuits coupled thereto, by integrating corresponding protection components (e.g., diodes), however the integration of these protection components is technologically complex and not always possible.

According to other solutions, the cap, of semiconductor material, is covered during the so-called "back-end" operations with a conductive layer, which is connected through a so-called wire bonding to a ground pad placed on an underlying substrate. However, this entails an increase in the thickness of the MEMS device, i.e. an increase in size along the so-called Z axis; furthermore, due to the shielding effect of the conductive layer, this solution is not feasible in the event that, for example, the MEMS device provides for the access of radiation inside the MEMS device.

According to other solutions, the electrical contact between the cap and the substrate is obtained through the formation of at least one vertical conductive path, so as not to incur an increase in the thickness of the MEMS device; however, this solution entails a considerable increase in the complexity of the manufacturing process.

<CIT> discloses an electronic device according to the preamble of claim <NUM>.

"<NPL> discloses a sensor device with a cap.

The aim of the present invention is therefore to provide a solution that overcomes at least in part the drawbacks of the prior art.

According to the present invention, a MEMS device and a manufacturing process are provided, as defined in the attached claims.

For a better understanding of the present invention, embodiments thereof are now described, purely by way of nonlimiting example, with reference to the attached drawings, wherein:.

<FIG> shows a first embodiment of the present MEMS device. In particular, <FIG> shows a device <NUM>, which forms a so-called TMOS ("Thermal-Metal-Oxide-Semiconductor") sensor, i.e. a sensor belonging to the category of micromachined NMOS-SOI sensors. For this reason, hereinafter reference will be made to TMOS device <NUM>.

In detail, the TMOS device <NUM> comprises a top substrate <NUM>, of semiconductive material (e.g., silicon), which is delimited by a first and a second surface S<NUM>, S<NUM>, which are parallel to an XY plane of an XYZ orthogonal reference system. The first surface S<NUM> is arranged below the second surface S<NUM>.

The top substrate <NUM> laterally delimits a first and a second recess <NUM>, <NUM>, which extend, without any loss of generality, on opposite sides of the top substrate <NUM>. Furthermore, the top substrate <NUM> forms a top cavity <NUM>, which is laterally offset with respect to the first and the second recesses <NUM>, <NUM> and extends upwards, from the first surface S<NUM>. In particular, and without any loss of generality, along the X axis the top cavity <NUM> extends between the first and the second recesses <NUM>, <NUM>.

Below the first surface S<NUM> there extends a first dielectric region <NUM>, which, although not shown, may be formed by one or more stacked insulating sub-regions, made for example of materials chosen from among: TEOS oxide, silicon nitride (SiN), silicon oxynitride (SiON). In particular, the first dielectric region <NUM> extends in direct contact with the overlying top substrate <NUM>.

In greater detail, the first dielectric region <NUM> laterally delimits part of the top cavity <NUM> and furthermore extends laterally with respect to the overlying top substrate <NUM>, so as to delimit the first recess <NUM> downwardly; in other words, part of the first dielectric region <NUM> faces the first recess <NUM>.

The TMOS device <NUM> also comprises a conductive region <NUM>, which is made, for example, of metal material (e.g., a material chosen from among: Al, AlCu, Cu, Au, Ti, TiW or a combination thereof) and extends in contact with the first dielectric region <NUM>.

In particular, the conductive region <NUM> comprises a main portion <NUM>, which extends below the first dielectric region <NUM>, and a first and a second secondary portion <NUM>, <NUM>, which form a single piece with the main portion <NUM>, are laterally offset from each other and traverse the first dielectric region <NUM>, up to facing the first surface S<NUM>. In practice, both the first and the second secondary portions <NUM>, <NUM> extend between the first surface S<NUM> and the underlying main portion <NUM>; furthermore, as clarified hereinafter, the first and the second secondary portions <NUM>, <NUM> form corresponding contact regions.

In greater detail, the first secondary portion <NUM> of the conductive region <NUM> extends below the top substrate <NUM>, wherewith it is in direct contact, while the second secondary portion <NUM> of the conductive region <NUM> is laterally offset with respect to the top substrate <NUM> and faces the first recess <NUM>; in other words, the first recess <NUM> is delimited downwardly by the second secondary portion <NUM> of the conductive region <NUM>, as well as by portions of the first dielectric region <NUM> adjacent to the second secondary portion <NUM> of the conductive region <NUM>. The second secondary portion <NUM> of the conductive region <NUM> is therefore exposed.

In greater detail, and without any loss of generality, along the X axis the second secondary portion <NUM> of the conductive region <NUM> is interposed between the first secondary portion <NUM> of the conductive region <NUM> and the top cavity <NUM>.

The TMOS device <NUM> further comprises a second dielectric region <NUM> (optional), which extends below the first dielectric region <NUM> and the conductive region <NUM>. In particular, although not shown, the second dielectric region <NUM> may be formed by one or more stacked insulating sub-regions, made for example of materials chosen from among: TEOS oxide, silicon nitride (SiN), silicon oxynitride (SiON).

The second dielectric region <NUM> contacts portions of the first dielectric region <NUM> which are laterally offset with respect to the conductive region <NUM>, as well as the main portion <NUM> of the conductive region <NUM>. Furthermore, the second dielectric region <NUM> laterally delimits part of the top cavity <NUM>.

The TMOS device <NUM> also comprises a bonding layer <NUM>, which is made for example of a glassy material (e.g., glass frit) and is arranged below the second dielectric region <NUM>, wherewith it is in direct contact.

In greater detail, the bonding layer <NUM> laterally delimits part of the top cavity <NUM>, which therefore extends through part of the top substrate <NUM>, as well as through the first and the second dielectric regions <NUM>, <NUM> and the bonding layer <NUM>.

As regards the second recess <NUM>, it is laterally delimited by a portion of the bonding layer <NUM> and by overlying portions of the top substrate <NUM> and of the first and the second dielectric regions <NUM>, <NUM>.

For practical purposes, the top substrate <NUM>, the first and the second dielectric regions <NUM>, <NUM> and the conductive region <NUM> form a cap <NUM>.

The TMOS device <NUM> further comprises a sensor device <NUM>, which is fixed to the cap <NUM> through the bonding layer <NUM>, as described in greater detail below.

The sensor device <NUM> comprises a bottom substrate <NUM> and an intermediate substrate <NUM>, both of semiconductor material (e.g., silicon), and having an intermediate bonding region <NUM> extending therebetween. In particular, the intermediate bonding region <NUM> is made for example of glassy material (e.g., glass-frit) and contacts the bottom substrate <NUM> and the intermediate substrate <NUM>.

In greater detail, the bottom substrate <NUM> is delimited upwardly by a front surface Stop, parallel to the XY plane. Furthermore, the bottom substrate <NUM> laterally and downwardly delimits a bottom cavity <NUM>, which extends in part below the front surface Stop.

The intermediate bonding region <NUM> extends on the front surface Stop. The bottom cavity <NUM> also extends through the intermediate bonding region <NUM>; in practice, part of the bottom cavity <NUM> is laterally delimited by the intermediate bonding region <NUM>.

The intermediate substrate <NUM> comprises a fixed portion <NUM>, which contacts the underlying intermediate bonding region <NUM>, and a respective suspended portion <NUM>, which is suspended on the bottom cavity <NUM> and, although not shown, is fixed to the fixed portion <NUM>.

The sensor device <NUM> further comprises a front region <NUM>, which comprises a peripheral portion <NUM>, which extends on the fixed portion <NUM> of the intermediate substrate <NUM>, and an internal portion <NUM>, which is suspended on the bottom cavity <NUM>. Part of the internal portion <NUM> of the front region <NUM> overlies part of the suspended portion <NUM> of the intermediate substrate <NUM>.

In greater detail, although not shown, the front region <NUM> is formed by respective sub-regions made for example of oxide, conductive and semiconductor material. Furthermore, in a per se known manner, the internal portion <NUM> of the front region <NUM> forms a detection structure <NUM>, described below. Part of the peripheral portion <NUM> of the front region <NUM> delimits the second recess <NUM> downwardly.

In still greater detail, and without any loss of generality, the top cavity <NUM> and the bottom cavity <NUM> are approximately vertically aligned. Furthermore, the mechanical coupling of the cap <NUM> to the sensor device <NUM> is such that the top cavity <NUM> and the bottom cavity <NUM> form a chamber <NUM>, wherein the detection structure <NUM> extends. In practice, the detection structure <NUM> is interposed between the top cavity <NUM> and the bottom cavity <NUM>; furthermore, without any loss of generality, the detection structure <NUM> is such that, although not visible in <FIG>, there is communication between the top cavity <NUM> and the bottom cavity <NUM>. Again without any loss of generality, the chamber <NUM> may be hermetic.

The detection structure <NUM> is of a per se known type; in particular, the detection structure <NUM> comprises, for example, a first and a second array <NUM>, <NUM> of elements sensitive to temperature changes induced by infrared radiation; in particular, in the present example, the sensitive elements are formed by corresponding suspended MOSFET transistors (not shown) which operate below threshold. In practice, the detection structure <NUM> is an active region of suspended type.

Again without any loss of generality, the first and the second arrays <NUM>, <NUM> are laterally offset from each other, as well as with respect to the suspended portion <NUM> of the intermediate substrate <NUM>, which acts as a mechanical support. The first and the second arrays <NUM>, <NUM> have therefore been previously released with respect to the intermediate substrate <NUM>.

In addition, the TMOS device <NUM> comprises a shield <NUM>, which is formed by metal material and is arranged on the second surface S<NUM> of the top substrate <NUM> of the cap <NUM>, so as to be approximately vertically aligned with the underlying second array <NUM>. In this manner, the shield <NUM> shields the underlying second array <NUM>, which acts as a reference, from the infrared radiation arriving from the outside; conversely, the first array <NUM> is laterally offset with respect to the shield <NUM>, so as to be exposed to the infrared radiation, which impinges precisely on the first array <NUM> after having traversed the overlying portion of the top substrate <NUM>.

In use, the first array <NUM> generates, in a per se known manner, electrical signals indicative of the intensity of the impinging infrared radiation, while the second array <NUM> generates electrical signals which may be used as a reference in a subsequent processing step of known type, for example to compensate for possible variations of the electrical signals generated by the first array <NUM> and caused by temperature variations independent of the infrared radiation, which therefore affect the first and the second arrays <NUM>, <NUM> in the same manner.

In order to receive the electrical signals generated by the first and the second arrays <NUM>, <NUM>, the sensor device <NUM> comprises a plurality of pads <NUM> of conductive material (only one shown in <FIG>) and a plurality of conductive paths <NUM> (only one shown in <FIG>), also of conductive material, not necessarily equal to the conductive material of the pads. For example, the pads <NUM> and the conductive paths <NUM> may be of a metal material, such as for example a material chosen from among: Al, AlCu, Cu, Au, Ti, TiW or a combination thereof.

In greater detail, the pads <NUM> extend on the part of the peripheral portion <NUM> of the front region <NUM> which delimits the second recess <NUM> downwardly, therefore they face the second recess <NUM>. Furthermore, in a per se known manner, the pads <NUM> are connected to corresponding sensitive elements of the first and the second arrays <NUM>, <NUM>, through corresponding conductive paths <NUM>, so as to receive electrical signals generated by the sensitive elements. In <FIG>, for simplicity of visualization, the connection between the conductive path <NUM> and the corresponding array is not visible. Furthermore, hereinafter it is assumed, for the sake of brevity, that only one pad <NUM> is present.

This having been said, a first wire bonding <NUM> extends between the first secondary portion <NUM> of the conductive region <NUM> and a reference potential region (not visible in <FIG>), as explained hereinafter with reference to <FIG>, wherein the TMOS device <NUM> is shown in a schematic and simplified manner.

In detail, <FIG> show a packaged system <NUM>, which comprises an electronic system <NUM> and a package dielectric region <NUM>, formed for example by a resin.

The electronic system <NUM> comprises the TMOS device <NUM> and a semiconductive die <NUM>.

In a per se known manner, the semiconductive die <NUM> comprises a respective semiconductor body <NUM>, wherein an ASIC circuit <NUM> is integrated, and is delimited by a respective top surface Sdie. Although not shown, in a per se known manner the semiconductive die <NUM> may comprise further regions (e.g., dielectric regions and conductive regions) with respect to the semiconductor body <NUM>. Furthermore, a plurality of conductive pads <NUM> (only two shown in <FIG>) extend over the top surface Sdie; hereinafter, the conductive pads <NUM> are referred to as the die pads <NUM>.

The TMOS device <NUM> overlies the semiconductive die <NUM>, whereto it is fixed, by interposing an adhesive region <NUM> (formed for example by polymeric material). The die pads <NUM> are laterally offset with respect to the adhesive region <NUM>, so as to be exposed.

In addition, the packaged system <NUM> comprises a support structure <NUM>, which comprises a planar region <NUM> of dielectric material, having the semiconductive die <NUM> fixed thereon, and a plurality of conductive pads <NUM> (only one shown in <FIG>), which are referred to as the support pads <NUM>; the support pads <NUM> are laterally offset with respect to the semiconductive die <NUM> and are electrically coupleable to the outside world.

This having been said, the first wire bonding <NUM> may connect the first secondary portion <NUM> of the conductive region <NUM> to a corresponding die pad <NUM> (as in the example shown in <FIG>), which in turn may contact the semiconductor body <NUM> of the semiconductive die <NUM>, this semiconductor body <NUM> forming the ground of the electronic system <NUM>.

Alternatively, as shown in <FIG>, the first wire bonding <NUM> may connect the first secondary portion <NUM> of the conductive region <NUM> to a corresponding support pad <NUM>, which in turn is grounded in use.

In practice, the first wire bonding <NUM> allows the conductive region <NUM>, and therefore also the top substrate <NUM> of the cap <NUM> to be grounded, owing to the contact present between the latter and the second secondary portion <NUM> of the conductive region <NUM>. Furthermore, since the conductive region <NUM> extends below the top substrate <NUM> and the first secondary portion <NUM> of the conductive region <NUM> faces the first recess <NUM>, the first wire bonding <NUM> extends from a reduced height (i.e., from the maximum height, along the Z axis, of the first secondary portion <NUM> of the conductive region <NUM>), rather than from the second surface S<NUM> of the top substrate <NUM>, and furthermore it may bend in the direction of the corresponding support pad <NUM> (or support pad <NUM>) without first having to exceed the height of the second surface S<NUM> of the top substrate <NUM>.

In practice, owing to the fact that the first secondary portion <NUM> of the conductive region <NUM> is arranged laterally with respect to the top substrate <NUM> and at a lower height with respect to the height of the second surface S<NUM>, a reduction in the height extension of the first wire bonding <NUM> is obtained. Conversely, if for example the first secondary portion <NUM> faced a cavity passing through the top substrate <NUM>, the first wire bonding <NUM> should in any case exceed the height of the second surface S<NUM> of the top substrate <NUM>, before being able to bend in the direction of the corresponding support pad <NUM> (or support pad <NUM>), with a consequent increase in thickness along the Z axis of the packaged system <NUM>.

The present solution therefore allows reducing the thickness along the Z axis of the packaged device <NUM>, while continuing to make use of the wire bonding technology, which is inexpensive and easy to implement.

In addition, as shown in <FIG> with reference to the only pad <NUM> visible, the TMOS device <NUM> comprises, for each pad <NUM>, a corresponding second wire bonding <NUM>, which connects the pad <NUM> to a corresponding die pad <NUM>, as shown in <FIG>, in order to allow the transfer of the electrical signals generated by the sensitive elements of the first and the second arrays <NUM>, <NUM> to the ASIC circuit <NUM>, which is configured to process the received electrical signals. Although not shown, one or more of the conductive pads <NUM> may also be used to transfer one or more electrical signals generated by the ASIC circuit <NUM> to corresponding conductive pads <NUM>.

Also in the case of the second wire bondings <NUM>, the same considerations made with regard to the first wire bonding <NUM> apply as far as the reduced vertical extension is concerned. In fact, the second wire bondings <NUM> extend from the pads <NUM>, which are arranged laterally with respect to the cap <NUM> and at a lower height with respect to the height of the second surface S<NUM>, therefore they my bend in the direction of the corresponding die pads <NUM> without first having to exceed the height of the second surface S<NUM> of the top substrate <NUM>.

Finally, <FIG> show how the package dielectric region <NUM> extends over the support structure <NUM>, incorporating the electronic system <NUM>, surrounding it laterally. Without any loss of generality, the package dielectric region <NUM> leaves exposed the second surface S<NUM> of the top substrate <NUM> of the cap <NUM>. Furthermore, the package dielectric region <NUM> extends into the first and the second recesses <NUM>, <NUM> and incorporates the first wire bonding <NUM> and the second wire bondings <NUM>.

<FIG> shows a different embodiment. In particular, <FIG> shows a MEMS device <NUM>, which, purely by way of example, is an inertial sensor.

The MEMS device <NUM> comprises the cap, here indicated by <NUM> and described hereinafter limitedly to the differences with respect to what has been shown in <FIG>. Elements already present in the cap <NUM> are indicated with the same reference signs.

In detail, the shield <NUM> is absent. The sensor device, here indicated by <NUM>, is, as previously mentioned, an inertial sensor; for example, hereinafter it is assumed, purely by way of example, that the sensor device <NUM> is a MEMS accelerometer.

In greater detail, the sensor device <NUM> comprises the bottom substrate, here indicated by <NUM>, which is still delimited upwardly by the front surface Stop.

Above the front surface Stop there extends an insulating region <NUM> which, although not shown, may be formed by one or more stacked insulating sub-regions, made for example of materials chosen from among TEOS oxide (possibly, doped) and thermal oxide.

The insulating region <NUM> is delimited upwardly by a respective front surface S<NUM>, parallel to the XY plane. Furthermore, conductive paths <NUM> (one visible in <FIG>) extend inside the insulating region <NUM>.

In addition, the sensor device <NUM> comprises the bottom cavity, here indicated by <NUM> and extending inside part of the insulating region <NUM>, from the front surface S<NUM>. Furthermore, the top cavity <NUM> is superimposed on the bottom cavity <NUM> so as to form the chamber, here indicated by <NUM>.

The sensor device <NUM> further comprises one or more windows <NUM> (one visible in <FIG>), each of which is laterally offset with respect to the bottom cavity <NUM> and extends through part of the insulating region <NUM>, from the front surface S<NUM>, up to facing an underlying corresponding conductive path <NUM>.

The sensor device <NUM> further comprises a structural layer <NUM> of polycrystalline silicon, for example formed by deposition.

In detail, the structural layer <NUM> extends, in direct contact, on the insulating region <NUM>, as well as inside the windows <NUM>, so as to contact the conductive paths <NUM>.

In greater detail, the structural layer <NUM> is traversed by a plurality of openings <NUM>, each of which entirely traverses the structural layer <NUM> and faces the bottom cavity <NUM> or the insulating region <NUM> downwardly.

Again purely by way of example, the openings <NUM> laterally delimit: a plurality of portions <NUM> of the structural layer <NUM>, referred to as the coupling portions <NUM> (one shown in <FIG>), the bottom parts of the coupling portions <NUM> extending inside corresponding windows <NUM>, so as to contact corresponding conductive paths <NUM>; a portion <NUM> of the structural layer <NUM>, referred to as the main portion <NUM>, which contacts corresponding portions of the underlying insulating region <NUM>; and a plurality of suspended portions <NUM>, which are suspended above the bottom cavity <NUM> and form, for example, a movable mass <NUM> and a first and a pair of springs <NUM>, each of which connects a respective end of the movable mass <NUM> to the main portion <NUM>.

In greater detail, the springs <NUM> and the movable mass <NUM> extend between the top cavity <NUM> and the bottom cavity <NUM>, inside the chamber <NUM>. Furthermore, the openings <NUM> which delimit the springs <NUM> and the movable mass <NUM> put the top cavity <NUM> and the bottom cavity <NUM> in communication with each other. In practice, the main portion <NUM> of the functional layer <NUM> laterally delimits a volume <NUM>, which faces, on one side, the top cavity <NUM> and, on the other side, the bottom cavity <NUM>; the springs <NUM> and the movable mass <NUM> extend into the volume <NUM>.

The springs <NUM> are deformable so as to allow the movable mass <NUM> to translate parallel to the X axis, as a function of the acceleration whereto the sensor device <NUM> is subject. In this regard, the sensor device <NUM> may for example be a MEMS accelerometer with detection of capacitive type, i.e. it is assumed that the variations of position of the movable mass <NUM> induced by the acceleration to be measured are transduced into corresponding capacitance variations of a detection capacitor (not shown). Furthermore, again by way of example, it is assumed that one or more of the conductive paths <NUM> are electrically connected to the detection capacitor, so as to receive electrical signals indicative of the aforementioned capacitance variations and, therefore, of the acceleration value to be measured.

In greater detail, each coupling portion <NUM> has, for example, an approximately cylindrical (or prismatic) shape and is separated from the main portion <NUM>. Furthermore, the coupling portions <NUM> face the second recess <NUM> upwardly, therefore they are laterally offset with respect to the cap <NUM>.

On each coupling portion <NUM> there extends a corresponding pad <NUM> of conductive material (e.g., a material chosen from among: Al, AlCu, Cu, Au, Ti and TiW or a combination thereof), which hereinafter is referred to as the connection pad <NUM>. In <FIG> only one connection pad <NUM> is visible.

Although not shown in <FIG>, each connection pad <NUM> is connected through a corresponding second wire bonding (here indicated by <NUM>) to a corresponding die pad <NUM> of the semiconductive die <NUM>, in the same manner described with reference to <FIG> and <FIG>, so as to allow the ASIC circuit <NUM> to receive the aforementioned electrical signals indicative of the acceleration value to be measured.

As regards the first wire bonding <NUM>, although not further shown, it connects the second secondary portion <NUM> of the conductive region <NUM> alternatively to a corresponding die pad <NUM> or to a corresponding support pad <NUM>, as already described with reference to <FIG>.

In practice, the first wire bonding <NUM> has the same arrangement, with respect to the cap <NUM>, described with reference to the embodiment shown in <FIG>; furthermore, again with respect to the cap <NUM>, the connection pads <NUM> have substantially the same arrangement as the pads <NUM> shown in <FIG>. Consequently, also the embodiment shown in <FIG> allows obtaining the same advantages described with reference to the embodiment shown in <FIG>. The embodiment shown in <FIG> therefore differs from the embodiment shown in <FIG> by the presence, in the chamber <NUM>, of a functional structure (formed by the springs <NUM> and by the movable mass <NUM>) for transducing a dynamic quantity (the acceleration) into one or more electrical signals, in lieu of the detection structure <NUM>.

The manufacturing process of the TMOS device <NUM> is described hereinafter.

In detail, as shown in <FIG>, a first semiconductive wafer <NUM> is initially provided, which comprises the top substrate <NUM> and a first layered dielectric region <NUM>, intended to form the first dielectric region <NUM>.

Then, as shown in <FIG>, two portions of the first layered dielectric region <NUM> are selectively removed, so as to form respectively a first and a second process window <NUM>, <NUM>, which face the top substrate <NUM>.

Subsequently, as shown in <FIG>, the conductive region <NUM> is formed, so that the first and the second secondary portions <NUM>, <NUM> extend respectively inside the first and the second process windows <NUM>, <NUM> and the main portion <NUM> overlies the first and the second secondary portions <NUM>, <NUM>.

Although not shown in detail, the conductive region <NUM> may be formed by depositing a metal layer on the first layered dielectric region <NUM> and inside the first and the second process windows <NUM>, <NUM> and subsequently selectively removing portions of the metal layer.

Then, as shown in <FIG>, a second layered dielectric region <NUM> is formed, on the conductive region <NUM> and on the exposed portions of the first layered dielectric region <NUM>, the second layered dielectric region <NUM> being intended to form the second dielectric region <NUM> (optional).

Subsequently, as shown in <FIG>, portions of the second layered dielectric region <NUM> and underlying portions of the first layered dielectric region <NUM> are selectively removed, so as to form a first and a second opening <NUM>, <NUM>, which are laterally offset with respect to the conductive region <NUM>. In particular, each of the first and the second process openings <NUM>, <NUM> faces a corresponding portion of the first surface S<NUM> of the top substrate <NUM>.

Then, as shown in <FIG>, a protective layer <NUM> is formed, which is made for example of resist and extends on the second layered dielectric region <NUM> and inside the first process opening <NUM>. The protective layer <NUM> leaves exposed portions of the first and the second layered dielectric regions <NUM>, <NUM> which delimit the second process opening <NUM>, therefore it does not extend inside the second process opening <NUM> and leaves exposed the portion of the first surface S<NUM> which forms the bottom of the second process opening <NUM>.

Subsequently, as shown in <FIG>, a selective removal (e.g., by dry etching) of a portion of the top substrate <NUM> is performed, from the portion exposed by the first surface S<NUM> which forms the bottom of the second process opening <NUM>; in this manner, the second process opening <NUM> partially penetrates the top substrate <NUM>. The protective layer <NUM> instead protects the portion of the top substrate <NUM> which forms the bottom of the first process opening <NUM>.

Subsequently, the protective layer <NUM> is removed. Furthermore, as shown in <FIG>, there may be performed a selective removal (e.g., by dry etching masked by the first and the second layered dielectric regions <NUM>, <NUM>) of a portion of the top substrate <NUM> which forms the bottom of the first process opening <NUM>, as well as of a further portion of the top substrate <NUM>, which forms the bottom of the second process opening <NUM>.

Subsequently, as shown in <FIG>, the bonding layer <NUM> is formed, for example by molding glassy material. The bonding layer <NUM> is laterally offset with respect to the first and the second process openings <NUM>, <NUM>.

Then, as shown in <FIG>, the first semiconductive wafer <NUM> is flipped over and is coupled to a second semiconductive wafer <NUM>, wherein the sensor device <NUM> has previously been formed, in a per se known manner. In particular, the coupling occurs so that the bonding layer <NUM> contacts the front region <NUM> of the sensor device <NUM>, as previously explained, as well as so that the pads <NUM> are arranged below the first process opening <NUM> and the detection structure <NUM> is arranged below the second process opening <NUM>. In practice, the second process opening <NUM> faces the detection structure <NUM> and forms the top part of the top cavity <NUM>, the bottom part of the top cavity <NUM> being laterally delimited by portions of the bonding layer <NUM>.

Then, although not shown and optionally, the top substrate <NUM> may be mechanically polished from the back, to reduce its thickness. At the end of this operation, the top substrate <NUM> is delimited upwardly by the second surface S<NUM>.

Subsequently, as shown in <FIG>, the shield <NUM> is formed and then there are selectively removed: a portion of the top substrate <NUM> which overlies the first process opening <NUM>, so as to form a through cavity <NUM>, which traverses the top substrate <NUM> and the first and the second layered dielectric regions <NUM>, <NUM>, which faces the underlying pads <NUM>; and a portion of the top substrate <NUM> overlying the first secondary portion <NUM> of the conductive region <NUM>, so as to expose the first secondary portion <NUM> of the conductive region <NUM> and form a preliminary cavity <NUM>. The preliminary cavity <NUM> traverses the top substrate <NUM> and faces the first secondary portion <NUM> of the conductive region <NUM> and adjacent portions of the first layered dielectric region <NUM> and is laterally offset with respect to the second secondary portion <NUM> of the conductive region <NUM>.

Then, singulation operations of the TMOS device <NUM> (shown in <FIG>) are performed from the group formed by the first and the second semiconductive wafers <NUM>, <NUM>. In practice, dicing operations of the group formed by the first and the second semiconductive wafers <NUM>, <NUM> are performed, along cutting lines CL, shown in <FIG>.

In particular, the cutting lines CL traverse the preliminary cavity <NUM> and the through cavity <NUM>, in such a way that, at the end of the dicing, the residual portions of the preliminary cavity <NUM> and of the through cavity <NUM> respectively form the first and the second recesses <NUM>, <NUM>. The residual portions of the first and the second layered dielectric regions <NUM>, <NUM> form respectively the first and the second dielectric regions <NUM>, <NUM>.

Then, although not further shown, the TMOS device <NUM> is coupled to the semiconductive die <NUM> which forms the ASIC circuit <NUM>, in a per se known manner. Subsequently, in a per se known manner, the first wire bonding <NUM> and the second wire bondings <NUM> are formed.

The manufacturing process of the MEMS device <NUM> is of the same type described with reference to the TMOS device <NUM>. In particular, the operations described with reference to <FIG> may be performed.

Then, as shown in <FIG>, the first semiconductive wafer <NUM> is flipped over and is coupled to a second semiconductive wafer, here indicated by <NUM>, wherein the sensor device <NUM> has previously been formed, in a per se known manner. In particular, the coupling is such that the connection pads <NUM> are arranged below the first process opening <NUM> and the springs <NUM> and the movable mass <NUM> are arranged below the second process opening <NUM>.

Subsequently, the manufacturing process continues in the same manner described with reference to the manufacturing of the TMOS device, therefore in the same manner described with reference to <FIG> and <FIG>, except for the formation of the shield <NUM>. Purely by way of example, <FIG> shows the group formed by the first and the second semiconductive wafers <NUM>, <NUM>, after performing the operations for forming the through cavity <NUM> and the preliminary cavity <NUM>, and before performing the singulation operations.

Also in the case of the MEMS device <NUM>, the first wire bonding <NUM> and the second wire bondings <NUM> are formed after the MEMS device <NUM> has been singulated and coupled to the semiconductive die <NUM> which forms the ASIC circuit <NUM>.

The advantages that the present solution affords are clear from the previous description.

In particular, the present MEMS device provides for a non-conductive bonding between the sensor device and the cap, whose semiconductive substrate may be grounded during the back-end operations (therefore, without having to provide preceding conductive vias), providing protection against electric discharges.

Finally, it is clear that modifications and variations may be made to the transducer device and the manufacturing process described and illustrated herein without thereby departing from the scope of the present invention, as defined in the attached claims.

For example, the bonding layer <NUM> and/or the intermediate bonding region <NUM> may be formed by an insulating material other than glass frit, such as for example organic material such as a so-called dry film or an epoxy glue or polymeric material.

As previously mentioned with reference to <FIG>, the second dielectric region <NUM> is optional and therefore may be absent. In this case, the bonding layer <NUM> may contact, as well as the first dielectric region <NUM>, also the conductive region <NUM>.

The sensor device may be different from what has been described and therefore may be configured to transduce into at least one electrical signal a different quantity with respect to what has been described, such as for example an angular speed or a radiation other than infrared.

For example, embodiments of the type shown in <FIG> are possible, but wherein the sensor device is configured to transduce a different physical or chemical quantity. For example, the detection structure <NUM> may comprise a membrane (not shown) configured to vary its resistance as a function of the amount of a chemical species (e.g., carbon monoxide, sulfur dioxide or zinc oxide) present in the chamber <NUM>, which is not hermetic.

The top cavity <NUM> may have a more limited thickness with respect to what has been described, and in particular may extend from the first surface S<NUM>, rather than partially penetrate the top substrate <NUM>.

Furthermore, the protective layer <NUM> may be omitted, in which case the operations referred to in <FIG> also entail the removal of the aforementioned portion of the top substrate <NUM> which forms the bottom of the first process opening <NUM>. Consequently, at the end of the operations referred to in <FIG>, the first and the second process openings <NUM>, <NUM> have a same depth; furthermore, the operations referred to in <FIG> are not performed.

Variations are also possible wherein the first and the second recesses <NUM>, <NUM> are arranged on a same side of the top substrate <NUM>. In other words, as qualitatively shown in <FIG> with reference, by way of example, to the embodiment shown in <FIG> and to a single pad <NUM>, the second secondary portion <NUM> of the conductive region <NUM> and the pad <NUM> may be placed on a same side of the top substrate <NUM>, in which case they are offset along the Y axis, are still arranged at different heights and are for example aligned parallel to the X axis; in practice, the first and the second recesses <NUM>, <NUM> communicate with each other and form a single recess. For the sake of simplicity, in <FIG> the first and the second wire bondings <NUM>, <NUM> are not shown; furthermore, <FIG> shows in a simplified manner the cap <NUM> and the sensor device <NUM>, without showing the relative regions in detail.

In general, the conductive region may also be of the type shown in <FIG>. In particular, the conductive region, here indicated by <NUM>, has an approximately planar shape and extends below the first surface S<NUM>. A first part <NUM> of the conductive region <NUM> is laterally offset with respect to the top substrate <NUM>, so as to face the first recess <NUM>; a second part <NUM> of the conductive region <NUM> is arranged to the side of the first part <NUM> and contacts an overlying portion of the top substrate <NUM>. The first wire bonding <NUM> contacts the first part <NUM> of the conductive region <NUM>. The corresponding manufacturing process provides, with reference to the operations shown in <FIG>, for the formation of a single process window, rather than the first and a second process window <NUM>, <NUM>.

Regarding the manufacturing process, it is possible that, after performing the operations shown with reference to <FIG>, and therefore after forming the first and the second process windows <NUM>, <NUM>, an ion implantation process is performed in the portions of top substrate <NUM> facing the second process window <NUM>, so as to reduce the contact resistance between the semiconductor of the top substrate <NUM> and the conductive region <NUM>. In fact, in this manner the second secondary region <NUM> of the conductive region <NUM> contacts an enriched portion of the top substrate <NUM>. Alternatively, the ion implantation may occur before the formation of the first layered dielectric region <NUM>.

Claim 1:
An electronic device comprising:
- a MEMS sensor device (<NUM>;<NUM>) including a functional structure (<NUM>;<NUM>,<NUM>) configured to transduce a chemical or physical quantity into a corresponding electrical quantity;
- a cap (<NUM>) comprising a semiconductive substrate (<NUM>); and
- a bonding dielectric region (<NUM>), which mechanically couples the cap (<NUM>) to the MEMS sensor device (<NUM>; <NUM>);
and wherein the cap (<NUM>) further comprises a conductive region (<NUM>;<NUM>), which extends between the semiconductive substrate (<NUM>) and the MEMS sensor device (<NUM>;<NUM>) and includes:
- a first portion (<NUM>;<NUM>); and
- a second portion (<NUM>;<NUM>), which contacts the semiconductive substrate (<NUM>);
characterized in that the first portion (<NUM>;<NUM>) is arranged laterally with respect to the semiconductive substrate (<NUM>) and is exposed, so as to be electrically coupleable to a terminal at a reference potential (<NUM>,<NUM>) by a corresponding wire bonding (<NUM>).