Patent Description:
<CIT> describes an integrated circuit including: a semiconductor substrate of a first conductivity type having at least one well of a second conductivity type laterally delimited, on two opposite walls, by regions of the first conductivity type, defined at its surface; at least one region of the second conductivity type which extends in the semiconductor substrate under the well; and a system for detecting a variation of the substrate resistance between each association of two adjacent regions of the first conductivity type.

<CIT> describes a device for detecting a laser attack in an integrated circuit chip formed in the upper P-type portion of a semiconductor substrate incorporating an NPN bipolar transistor having an N-type buried layer, including a detector of the variations of the current flowing between the base of said NPN bipolar transistor and the substrate.

<CIT> describes a chip comprising a transistor level, a semiconductor region in, below, or in and below the transistor level, a test signal circuit configured to supply a test signal to the semiconductor region, a determiner configured to determine a behavior of the semiconductor region in response to the test signal and a detector configured to detect a change of geometry of the semiconductor region based on the behavior and a reference behavior of the semiconductor region in response to the test signal.

<CIT> describes a method of measuring the thickness of a semiconductor substrate. First, a semiconductor substrate having a thickness and a photocurrent generating structure is provided. Next, the semiconductor substrate is exposed to a light source and a current generated by the light source is measured across the photocurrent generating structure. Finally, the thickness of the semiconductor substrate is determined by the current measurement.

Embodiments of devices and method for detecting semiconductor substrate thickness are disclosed. In accordance with the present disclosure, an IC device is provided as defined in claim <NUM>.

In an embodiment, the response analysis unit is configured to generate thickness information of the semiconductor substrate based on the magnitude of the response signal.

In an embodiment, the thickness information of the semiconductor substrate includes information regarding the change in the thickness of the semiconductor substrate.

In an embodiment, the charge emitter includes a diode.

In an embodiment, the charge emitter includes a bipolar transistor.

In an embodiment, the charge sensor includes a diode.

In an embodiment, the charge sensor includes a bipolar transistor.

Furthermore, in accordance with the present disclosure, a method for detecting semiconductor substrate thickness is conceived as defined in claim <NUM>.

In an embodiment, the method further involves generating thickness information of the semiconductor substrate based on the response signal.

Other aspects and advantages of embodiments of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by this detailed description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Reference throughout this specification to "one embodiment," "an embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with the indicated embodiment is included in at least one embodiment of the present invention. Thus, the phrases "in one embodiment," "in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

<FIG> depicts an IC device <NUM> with substrate thickness detection capabilities in accordance with an embodiment of the invention. In the example which does not fall within the scope of the claimed invention depicted in <FIG>, the IC device includes a semiconductor substrate <NUM>, an IC <NUM>, a charge emitter <NUM>, and a charge sensor <NUM>. Although the illustrated IC device is shown with certain components and described with certain functionality herein, other embodiments of the IC device may include fewer or more components to implement the same, less, or more functionality. For example, although the illustrated IC device is shown with one IC, one charge emitter, and one charge and this particular example would not fall within the scope of the claimed invention, in other embodiments which would fall within the scope of the claimed invention, the IC device may include multiple ICs, multiple charge emitters, and/or multiple charge sensors. In addition to substrate thickness detection capabilities, the IC device may include other data integrity and/or security features.

The semiconductor substrate <NUM> of the IC device <NUM> can be implemented as any suitable material. Examples of the materials that can be used for the semiconductor substrate include, without being limited to, silicon and GaAs.

The IC <NUM>, the charge emitter <NUM>, and the charge sensor <NUM> of the IC device <NUM> are embedded in the semiconductor substrate <NUM>. In the embodiment depicted in <FIG>, the IC performs designated functions of the IC device <NUM>. The IC may be a logic circuit, such as a logic circuit residing in p-wells and/or n-wells. Examples of the IC include, without being limited to, memory circuits, microcontrollers, and secure element logic circuits. The charge emitter is configured to produce an electrical charge in the semiconductor substrate. The charge emitter may be a diode, a bipolar transistor, or other suitable electrical charge emission device. In the embodiments which fall within the scope of the claimed invention, the charge emitter is configured to emit an electrical charge into the semiconductor substrate. In some embodiments, the charge emitter is configured to generate light that is radiated into the semiconductor substrate, which causes an electrical charge to be produced in the semiconductor substrate. The charge sensor is used to collect or capture at least a fraction of the electrical charge or electrons that are injected into the semiconductor substrate by the charge emitter. In the embodiment which falls within the scope of the claimed invention depicted in <FIG>, the charge sensor is configured to generate a response signal in response to the electrical charge produced in the semiconductor substrate. The charge sensor may be a diode, a bipolar transistor, or other suitable electrical charge reception device.

The IC <NUM>, the charge emitter <NUM>, and the charge sensor <NUM> is embedded in the semiconductor substrate <NUM> during the manufacturing process. For example, the IC, the charge emitter, and the charge sensor are embedded in the semiconductor substrate through the process used to fabricate the IC device <NUM>. In an embodiment, the IC, the charge emitter, and the charge sensor are fabricated using known semiconductor fabrication techniques, including, for example known Complementary metal-oxide-semiconductor (CMOS) processing techniques. Because the charge emitter and the charge sensor are embedded in the semiconductor substrate, the electrical charge produced by the charge emitter travels through the semiconductor substrate before reaching the charge sensor. The magnitude of electrical charge reaching the charge sensor, and thus the magnitude of the response signal generated by the charge sensor depends on the thickness of the semiconductor substrate. For example, generally a fraction of the electrical charge produced by the charge emitter is collected by the charge sensor. The magnitude of the produced electrical charge collected by the charge sensor depends on geometrical aspects of the IC device, which includes the distance between the charge emitter and the charge sensor, the thickness of the semiconductor substrate, and the size of the charge collector. Thus, the magnitude of the charge collected by the charge sensor can be used as an indicator of substrate thickness and/or changes in substrate thickness.

<FIG> is a graph of detected charge versus the distance between the charge emitter <NUM> and the charge sensor <NUM> of the IC device <NUM> depicted in <FIG> for three different substrate thicknesses. In the examples, the magnitude of the detected charge is expressed as Isensor/Iinject. In the plot shown in <FIG>, the magnitude of the resulting current ratio decreases as the distance between the charge emitter and the charge sensor increases. The decrease in the magnitude of the current ratio becomes steeper when the semiconductor substrate <NUM> is thinner. Specifically, the decrease in the magnitude of the current ratio in the curve <NUM>, in which the substrate thickness is equal to <NUM> is steeper than the decrease in the magnitude of the current ratio in the curve <NUM>, in which the substrate thickness is equal to <NUM>. In addition, the decrease in the magnitude of the current ratio in the curve in which the substrate thickness is equal to <NUM> is steeper than the decrease in the magnitude of the current ratio in the curve <NUM>, in which the substrate thickness is equal to <NUM>. The curve in which the substrate thickness is equal to <NUM> starts deviating from the original direction of the curve after the distance between the charge emitter and the charge sensor becomes larger than the substrate thickness.

<FIG> illustrates charge injection by the charge emitter <NUM> and electron collection by the charge sensor <NUM> given a particular semiconductor substrate thickness. As depicted in <FIG>, doped wells <NUM>, <NUM>, <NUM> of the IC <NUM> (depicted in <FIG>), which include electrical contacts, are located between the charge emitter and the charge sensor. Generally, N-wells can collect electrons while p-wells collect holes. The electrons emitted from the charge can be divided into a group, Qs, of electrons, which flow close to the surface of the semiconductor substrate (as represented by lines <NUM>, <NUM>, <NUM>, <NUM>), and a group, Qd, of electrons, which follow trajectories (as represented by lines <NUM>, <NUM>) deep into the semiconductor substrate. The charge, Qsensor, arriving at the charge sensor can be represented as: <MAT> where Fs and Fd represent the fractions of electrons arriving at the charge sensor. Thinning the semiconductor substrate may significantly affect the fraction, Fd, of electrons, Qd, following trajectories deep into the semiconductor substrate, but tends not to significantly affect the fraction, Fs, of electrons, Qs, flowing close to the surface of the semiconductor substrate. To detect substrate thinning, the sensor signal is compared with a reference value measured with the original substrate thickness. Because the fraction value, Fs, is less thickness-dependent, the term Fs•Qs is effectively an offset term, which adds noise to the comparison between the sensor signal and the reference value. To increase signal-to-noise, the fraction value, Fs, should be kept low. As shown in <FIG>, electrons following a trajectory close to the substrate surface have a good chance of being captured by the n-wells. Consequently, the fraction, Fs, of surface electrons reaching the charge sensor is low. Therefore, doped regions between the charge emitter and the charge sensor can improve the signal-to-noise ratio for detection of substrate thinning.

The IC device <NUM> depicted in <FIG> uses the charge emitter <NUM> and the charge sensor <NUM> that are embedded in the IC device to detect the thickness of the semiconductor substrate <NUM>. Consequently, the IC device depicted in <FIG> does not need external emission and sensor devices to detect the thickness of the semiconductor substrate. Such an embedded detection technique is desirable, because the IC device may be the sole hardware component that supports an application. Based on the detection of thickness change, the IC device depicted in <FIG> can be configured to perform security actions and/or trigger security actions to thwart an attack on data or data operations (e.g., the IC device may re-compute or reversely compute, go into a safe mode, or switch itself off permanently). Consequently, compared to an IC device that measures substrate thickness by applying beams of light to a substrate of an IC device using an external light source, the IC device depicted in <FIG> can have reduced silicon area overhead, improved computation time, and reduced power consumption.

In the embodiments which fall within the scope of the claimed invention, the IC device <NUM> depicted in <FIG> further includes a second charge emitter embedded in the semiconductor substrate <NUM> and configured to produce a second electrical charge in the semiconductor substrate. The IC device may also include a second charge sensor embedded in the semiconductor substrate and configured to generate a second response signal in response to the second electrical charge produced in the semiconductor substrate. The magnitude of the second response signal also depends on the thickness of the semiconductor substrate. By using more than one charge emitter and more than one corresponding charge sensor, the IC device can improve the accuracy of detecting substrate thickness. For example, multiple charge emitter/change sensor pairs may be used to detect thinning over a larger substrate area.

<FIG> depicts an embodiment of an IC system <NUM> with substrate thickness detection capabilities. In the embodiment depicted in <FIG>, the IC system includes an IC device <NUM>, an emitter controller <NUM>, and a response analysis unit <NUM>. The IC device includes a semiconductor substrate <NUM>, an IC <NUM>, a charge emitter <NUM>, and a charge sensor <NUM>. The emitter controller can be used to control the portion of charge that is produced in the substrate by the charge emitter. The response analysis unit can be used to analyze the signal generated by the charge sensor and to decide whether the substrate has been thinned. The emitter controller and the response analysis unit may be external to the IC device and this example would not fall within the scope of the claimed invention (e.g., not fabricated on the same substrate as the charge emitter and the charge sensor of the IC device) or the embodiment which does fall within the scope of the claimed invention is within the IC device (e.g., fabricated on the same substrate as the charge emitter and the charge sensor of the IC device). In some embodiments, the IC, the charge emitter, the charge sensor, the emitter controller, and the response analysis unit are embedded in the semiconductor substrate during the fabrication process. For example, the IC, the charge emitter, and the charge sensor are embedded in the semiconductor substrate through the process used to fabricate the IC device. In an embodiment, the IC, the charge emitter, and the charge sensor are fabricated using known semiconductor fabrication techniques, including, for example known CMOS processing techniques. The IC device <NUM> depicted in <FIG> is one possible embodiment of the IC device <NUM> depicted in <FIG>. Specifically, the semiconductor substrate <NUM>, the IC <NUM>, the charge emitter <NUM>, and the charge sensor <NUM> depicted in <FIG> are embodiments of the semiconductor substrate <NUM>, the IC <NUM>, the charge emitter <NUM>, and the charge sensor <NUM> depicted in <FIG>. However, the IC device <NUM> depicted in <FIG> is not limited to the embodiment shown in <FIG>. For example, in the embodiment depicted in <FIG>, the IC <NUM> includes two logic circuits <NUM>, <NUM> located in N-wells, two logic circuits <NUM>, <NUM> located in P-wells, and an electrical isolation element <NUM>, which may be an electrical insulator made of a dielectric material such as silicon oxide. However, although the IC device <NUM> is depicted in <FIG> as including multiple n-wells and p-wells, in other embodiments, the IC device includes a single n-well and/or a single p-well.

In the embodiments which fall within the scope of the claimed invention, the emitter controller <NUM> is configured to control the charge emitter <NUM> to produce a second electrical charge in the semiconductor substrate <NUM>. The charge sensor generates a second response signal in response to the second electrical charge. The response analysis unit <NUM> is configured to compare the second response signal to the previously generated response signal to determine a change in the thickness of the semiconductor substrate. In an embodiment, the second charge has the same magnitude as the previously produced electrical charge in order to detect substrate thickness change (e.g., caused by backside thinning).

The emitter controller <NUM> is configured to control the electrical charge that the charge emitter <NUM> produces in the semiconductor substrate <NUM>. The emitter controller can be implemented in hardware (e.g., as one or more logic circuits), software, firmware, or a combination thereof. In some embodiments, the emitter controller controls the charge emitter to periodically inject electrical charge, which can be more power-efficient than a charge emitter that constantly injects electrical charge. In an embodiment, the emitter controller includes a transistor that makes/breaks the connection to a bias voltage. In another embodiment, the emitter controller includes a current controller or voltage controller for controlling the charge emitter to inject various amounts of charge into the semiconductor substrate.

The response analysis unit <NUM> is configured to generate thickness information of the semiconductor substrate <NUM> based on the response signal from the charge sensor <NUM>. The response analysis unit can be implemented in hardware (e.g., as one or more logic circuits), software, firmware, or a combination thereof. In some embodiments, the response analysis unit detects whether the semiconductor substrate has been thinned based on the response signal from the charge sensor. In an embodiment, the sensor output for the nominal substrate thickness is known by the response analysis unit. Upon injection of charge into the substrate and charge detection at the charge sensor, the sensor output is compared to the known sensor output for nominal thickness and a change in substrate thickness can be detected from the comparison result. For example, if the magnitude of the sensor output is smaller than the magnitude of the known sensor output, it can be determined that the thickness of the semiconductor substrate has been reduced. If the magnitude of the sensor output is the same as the magnitude of the known sensor output (e.g., within an accepted range of, for example, ±<NUM>%), it can be determined that there has been no change in the thickness of the semiconductor substrate. In an embodiment, the known sensor output for nominal thickness is stored as an entry in a lookup table and the sensor output is compared to the entry in the lookup table. In some embodiments, time-coding or modulation is performed on the response signal to improve the signal-to-noise ratio.

In the embodiments falling within the scope of the claimed invention, the IC device <NUM> includes multiple charge emitters <NUM>. The IC device switches on all of the charge emitters simultaneously to increase the electrical charge gathered by the charge sensor <NUM>. An increased output signal from the charge sensor can make signal interpretation easier. In an alternative example which does not fall within the scope of the claimed invention, individual charge emitters or groups of charge emitters may be driven consecutively. The difference in response signals between the individual emitters or groups of charge emitters or the ratio of response signals to the individual emitters or groups of charge emitters can be used to extract more precise information about substrate thickness and/or to extract information without reference to a known sensor output for a nominal thickness.

In some examples, which do not fall within the scope of the claimed invention, the IC device <NUM> includes only one charge emitter <NUM> and multiple charge sensors <NUM>. In some other embodiments which do fall within the scope of the claimed invention, the IC device <NUM> includes multiple charge emitters and multiple charge sensors for monitoring the thickness of a large area of a substrate. Charge emitter and charge sensor pairs can be used to monitor the substrate thickness of particular areas within a large substrate area. The difference in response signals between the individual pairs of charge emitters and charge sensors or the ratio of response signals to the individual pairs of charge emitters and charge sensors can be used to extract information about substrate thickness or to extract information without reference to a known sensor output for a nominal thickness. For example, a first charge emitter and charge sensor pair may be embedded in a first section of a particular substrate area and a second charge emitter and charge sensor pair may be embedded in a second section of the particular substrate area. The first charge emitter and charge sensor pair can be used to extract substrate thickness information related to the first section while the second charge emitter and charge sensor pair can be used to extract substrate thickness information related to the second section. In another embodiment which falls within the scope of the claimed invention, more than two charge emitter/sensor pairs can be distributed laterally across the area of an IC device to provide substrate thinning detection over a wide area of the IC device.

<FIG> and <FIG> depict two embodiments of the charge emitter <NUM> depicted in <FIG> that are implemented as diodes with a p-type substrate. Charge emitters <NUM> and <NUM> depicted in <FIG> and <FIG>, respectively, are two possible embodiments of the charge emitter <NUM> depicted in <FIG>. However, the charge emitter <NUM> depicted in <FIG> is not limited to the embodiments shown in <FIG> and <FIG>.

<FIG> depicts an embodiment of the charge emitter <NUM> depicted in <FIG> that is implemented as a diode realized by an n++ doped region <NUM>. In the embodiment depicted in <FIG>, the semiconductor substrate <NUM> of the charge emitter <NUM> is a p-type substrate. The charge emitter <NUM> is realized by a PN-junction diode, formed by the n++ doped region, two shallow trench isolation (STI) units <NUM>-<NUM>, <NUM>-<NUM>, and the p-type substrate. When the negative bias voltage (diode voltage Vdiode<-Vt threshold voltage) is applied to the n++ doped region and the p-type substrate is grounded (the substrate voltage Vsub=<NUM>) through a P++ contact region <NUM>, the PN-junction diode is brought into a forward state and electrons are injected into the p-type substrate. The n++ doped region can be produced in the same process step as source and drain pads of p-channel metal-oxide semiconductor (PMOS) transistors.

<FIG> depicts an embodiment of the charge emitter <NUM> depicted in <FIG> that is implemented as a diode realized by an n-well region <NUM>, which is contacted by an n++ doped region <NUM>. In the embodiment depicted in <FIG>, the semiconductor substrate <NUM> is a p-type substrate. The charge emitter <NUM> is realized by a PN-junction diode, formed by the++ doped region, two STI units <NUM>-<NUM>, <NUM>-<NUM>, the n-well region, and the p-type substrate. When the negative bias voltage (diode voltage Vdiode<-Vt threshold voltage) is applied to the n++ doped region and the n-well region and the p-type substrate is grounded (the substrate voltage Vsub=<NUM>) through a P++ contact region <NUM>, the PN-junction diode is brought into a forward state and electrons are injected into the p-type substrate.

<FIG> and <FIG> depict two embodiments of the charge emitter <NUM> depicted in <FIG> that are implemented as on-chip light-emitting diodes (LEDs) with an n-type substrate. Charge emitters <NUM> and <NUM> depicted in <FIG> and <FIG>, respectively, are two possible embodiments of the charge emitter <NUM> depicted in <FIG>. However, the charge emitter <NUM> depicted in <FIG> is not limited to the embodiments shown in <FIG> and <FIG>.

<FIG> depicts an embodiment of the charge emitter <NUM> depicted in <FIG> that is implemented as a p++ doped region <NUM>. In the embodiment depicted in <FIG>, the semiconductor substrate <NUM> is an n-type substrate. The charge emitter <NUM> is realized by a PN-junction diode, formed by the p++ doped region, two STI units <NUM>-<NUM>, <NUM>-<NUM>, and the n-type substrate. When the positive bias voltage (diode voltage Vdiode>Vt threshold voltage) is applied to the p++ doped region and the n-type substrate is grounded (the substrate voltage Vsub=<NUM>) through an n++ contact region <NUM>, the charge emitter is brought into a forward state and holes are injected into the n-type substrate.

<FIG> depicts an embodiment of the charge emitter <NUM> depicted in <FIG> that is realized by a p-well region <NUM>, which is contacted by a p++ doped region <NUM>. In the embodiment depicted in <FIG>, the semiconductor substrate <NUM> is an n-type substrate. The charge emitter is realized by a PN-junction diode, formed by the p++ doped region, two STI units <NUM>-<NUM>, <NUM>-<NUM>, the p-well region, and the n-type substrate. When the positive bias voltage (diode voltage Vdiode>Vt threshold voltage) is applied to the p++ doped region and the n-type substrate is grounded (the substrate voltage Vsub=<NUM>) through an n++ contact region <NUM>, the charge emitter is brought into a forward state and electrons are injected into the n-type substrate.

<FIG> illustrates the generation of charge in the IC system <NUM> depicted in <FIG>. In the operation illustrated in <FIG>, the charge emitter <NUM> does not directly emit charge. Rather, the charge emitter is activated to generate light. Some of the light generated by the LED is radiated upwards. However, a portion of the light generated by the LED is radiated into the n-type substrate, as illustrated in <FIG>. In the n-type substrate, the light photons can produce electron-hole pairs <NUM>, e.g., in the vicinity of the light-emitting diode. These electrons or holes diffuse throughout the substrate as illustrated by charge transport lines <NUM>, <NUM> and a fraction of electrons or holes will be collected by the charge sensor <NUM>. The fraction of electrons collected by the charge sensor is thickness-dependent. In the embodiment depicted in <FIG>, the charge creation is also thickness-dependent. For example, light from the LED can produce electron-hole pairs when traveling through the substrate. But for thinned silicon, the light will travel through the substrate over a shorter distance, so less charge will be detected in the charge sensor.

<FIG> and <FIG> depict two embodiments of the charge sensor <NUM> depicted in <FIG> that are implemented as diodes with a p-type substrate. Charge sensors <NUM> and <NUM> depicted in <FIG> and <FIG>, respectively, are two possible embodiments of the charge sensor <NUM> depicted in <FIG>. However, the charge sensor <NUM> depicted in <FIG> is not limited to the embodiments shown in <FIG> and <FIG>.

<FIG> depicts an embodiment of the charge sensor <NUM> depicted in <FIG> that is implemented as a diode realized by an n++ doped region <NUM>. In the embodiment depicted in <FIG>, the semiconductor substrate <NUM> is a p-type substrate. The charge sensor <NUM> is realized by a PN-junction diode, formed by the n++ doped region, two STI units <NUM>-<NUM>, <NUM>-<NUM>, and the p-type substrate. When a positive bias voltage (diode voltage Vdiode>-Vt threshold voltage) is applied to the n++ doped region and the p-type substrate is grounded (the substrate voltage Vsub=<NUM>) through a P++ contact region <NUM>, the PN-junction diode is brought into a backward state and electrons can be collected at a diode depletion region <NUM> through the p-type substrate. The n++ doped region can be produced in the same process step as the source and drain pads of PMOS transistors.

<FIG> depicts an embodiment of the charge sensor <NUM> depicted in <FIG> that is implemented as a diode realized by an n-well region <NUM>, which is contacted by an n++ doped region <NUM>. In the embodiment depicted in <FIG>, the semiconductor substrate <NUM> is a p-type substrate. The charge sensor <NUM> is realized by a PN-junction diode, formed by the n++ doped region, the n-well region, two STI units <NUM>-<NUM>, <NUM>-<NUM>, and the p-type substrate. When a positive bias voltage (diode voltage Vdiode>-Vt threshold voltage) is applied to the n++ doped region and the n-well region and the p-type substrate is grounded (the substrate voltage Vsub=<NUM>) through a P++ contact region <NUM>, the PN-junction diode is brought into a backward state and electrons can be collected at a diode depletion region <NUM> through the p-type substrate.

<FIG> and <FIG> depict two embodiments of the charge sensor <NUM> depicted in <FIG> that are implemented as diodes with an n-type substrate. Charge sensors <NUM> and <NUM> depicted in <FIG> and <FIG>, respectively, are two possible embodiments of the charge sensor <NUM> depicted in <FIG>. However, the charge sensor <NUM> depicted in <FIG> is not limited to the embodiments shown in <FIG> and <FIG>.

<FIG> depicts an embodiment of the charge sensor <NUM> depicted in <FIG> that is implemented as a diode realized by a p++ doped region <NUM>. In the embodiment depicted in <FIG>, the semiconductor substrate <NUM> is an n-type substrate. The charge sensor <NUM> is realized by a PN-junction diode, formed by the p++ doped region, two STI units <NUM>-<NUM>, <NUM>-<NUM>, and the n-type substrate. When the negative bias voltage (diode voltage Vdiode<<NUM>) is applied to the p++ doped region and the p-type substrate is grounded (the substrate voltage Vsub=<NUM>) through a P++ contact region <NUM>, the PN-junction diode is brought into a backward state and electrons can be collected at a diode depletion region <NUM> through the n-type substrate. The p-type pad can be produced in the same process step as source and drain pads of PMOS transistors.

<FIG> depicts an embodiment of the charge sensor <NUM> depicted in <FIG> that is implemented as a diode realized by a p-well region <NUM>, which is contacted by a p++ doped region <NUM>. In the embodiment depicted in <FIG>, the semiconductor substrate <NUM> is an n-type substrate. The charge sensor <NUM> is realized by a PN-junction diode, formed by the p++ doped region, the p-well region, two STI units <NUM>-<NUM>, <NUM>-<NUM>, and the n-type substrate. When the negative bias voltage (diode voltage Vdiode<<NUM>) is applied to the p++ doped region and the n-well region and the p-type substrate is grounded (the substrate voltage Vsub=<NUM>) through a P++ contact region <NUM>, the PN-junction diode is brought into a backward state and electrons can be collected at a diode depletion region <NUM> through the n-type substrate.

The charge sensors <NUM> and <NUM> depicted in <FIG> and <FIG>, respectively, are sensitive to electrons injected into the semiconductor substrate. Those electrons that diffuse to the neighborhood of the charge sensors (e.g., more precisely to the depletion regions of the charge sensors) experience a diode potential, which pulls the electrons into the corresponding n++ doped region. These electrons contribute to the sensor output current.

The charge sensors <NUM> and <NUM> depicted in <FIG> and <FIG>, respectively, are sensitive to holes injected into the semiconductor substrate. Those holes that diffuse to the neighborhood of the charge sensors (e.g., more precisely to the depletion regions of the charge sensors) experience a diode potential, which pulls the holes into the corresponding p++ doped region. These holes contribute to the sensor output current.

<FIG> depicts an embodiment of the charge sensor <NUM> depicted in <FIG> that is implemented as a bipolar transistor. The charge sensor <NUM> depicted in <FIG> is one of the possible embodiments of the charge sensor <NUM> depicted in <FIG>. However, the charge sensor <NUM> depicted in <FIG> is not limited to the embodiment shown in <FIG>.

In the embodiment depicted in <FIG>, the semiconductor substrate <NUM> is a p-type substrate and the charge sensor <NUM> is a PNP bipolar transistor. The PNP bipolar transistor includes a p++ emitter <NUM> and an n-well base <NUM>. The n-well base of the PNP bipolar transistor is in contact with the semiconductor substrate, forming a collector-base diode depletion region <NUM>. In an example operation of the PNP bipolar transistor, electrons that diffuse into the neighborhood of the n-type base experience a potential, pulling them into the base while the p-type substrate is grounded (the substrate voltage Vsub=<NUM>) through a P++ contact region <NUM>. Thus, these electrons contribute to the base current of the PNP bipolar transistor. The base current gives rise to a current between the emitter and the corresponding collector. The output current of the charge sensor is the emitter-collector current, which is an amplified image of the emitter current. The amplified current can make signal interpretation easier. Alternatively, the charge sensor <NUM> can be implemented as a PNP bipolar transistor, which may include a p++ pad as an emitter and an n-well as a base.

<FIG> depicts a compact embodiment of the IC device <NUM> depicted in <FIG>. In the embodiment depicted in <FIG>, an IC device <NUM> is a bipolar junction transistor, which includes an emitter <NUM> (serving as a charge emitter), a base <NUM> (the p++ substrate), an STI region <NUM>, and a collector <NUM> (serving as a charge sensor). In the embodiment depicted in <FIG>, the collector current depends on the Gummel number (i.e., the total amount of dope charge in the base). Because the Gummmel number directly depends on the substrate thickness, the IC device can detect substrate thickness.

<FIG> is a process flow diagram of a method for detecting semiconductor substrate thickness in accordance with an embodiment of the invention. At block <NUM>, an electrical charge is produced in a semiconductor substrate using a charge emitter embedded in the semiconductor substrate. At block <NUM>, a response signal is generated in response to the electrical charge produced in the semiconductor substrate using a charge sensor embedded in the semiconductor substrate. The magnitude of the response signal depends on the thickness of the semiconductor substrate. The charge emitter may be the same or similar to the charge emitter <NUM> depicted in <FIG>, the charge emitter <NUM> depicted in <FIG>, the charge emitter <NUM> depicted in <FIG>, the charge emitter <NUM> depicted in <FIG>, the charge emitter <NUM> depicted in <FIG>, and/or the charge emitter <NUM> depicted in <FIG>. The charge sensor may be the same or similar to the charge sensor <NUM> depicted in <FIG>, the charge sensor <NUM> depicted in <FIG>, the charge sensor <NUM> depicted in <FIG>, the charge sensor <NUM> depicted in <FIG>, the charge sensor <NUM> depicted in <FIG>, the charge sensor <NUM> depicted in <FIG>, and/or the charge sensor <NUM> depicted in <FIG>.

It should also be noted that at least some of the operations for the methods may be implemented using software instructions stored on a computer useable storage medium for execution by a computer. As an example, an embodiment of a computer program product includes a computer useable storage medium to store a computer readable program that, when executed on a computer, causes the computer to perform operations, as described herein.

The computer-useable or computer-readable medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device), or a propagation medium. Examples of a computer-readable medium include a semiconductor or solid-state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disc, and an optical disc. Current examples of optical discs include a compact disc with read only memory (CD-ROM), a compact disc with read/write (CD-R/W), a digital video disc (DVD), and a Bluray disc.

In the above description, specific details of various embodiments are provided. However, some embodiments may be practiced with less than all of these specific details. In other instances, certain methods, procedures, components, structures, and/or functions are described in no more detail than to enable the various embodiments of the invention, for the sake of brevity and clarity.

Claim 1:
An Integrated Circuit, IC, device, the IC device comprising:
a semiconductor substrate (<NUM>);
a charge emitter (<NUM>, <NUM>) embedded in the semiconductor substrate (<NUM>, <NUM>) and configured to produce an electrical charge in the semiconductor substrate (<NUM>, <NUM>); and
a charge sensor (<NUM>, <NUM>) embedded in the semiconductor substrate (<NUM>, <NUM>) and configured to generate a response signal in response to the electrical charge produced in the semiconductor substrate (<NUM>, <NUM>), wherein the magnitude of the response signal depends on the thickness of the semiconductor substrate (<NUM>, <NUM>),
characterized in that the IC device further comprises an emitter controller (<NUM>) configured to control the magnitude of electrical charge produced by the charge emitter (<NUM>, <NUM>);
wherein the IC device further comprises at least one second charge emitter embedded in the semiconductor substrate (<NUM>, <NUM>) and configured to produce a second electrical charge in the semiconductor substrate (<NUM>, <NUM>), wherein the emitter controller (<NUM>) is further configured to control the at least one second charge emitter (<NUM>, <NUM>) to produce the second electrical charge in the semiconductor substrate (<NUM>, <NUM>) having the same magnitude as the electrical charge, wherein the charge sensor (<NUM>, <NUM>) generates a second response signal in response to the second electrical charge, and wherein the IC device further comprises a response analysis unit (<NUM>) configured to compare the second response signal to the response signal to determine a change in the thickness of the semiconductor substrate (<NUM>, <NUM>);
and wherein the IC device is configured to switch on the first charge emitter and the at least one second charge emitter simultaneously to increase the response signal generated by the charge sensor (<NUM>, <NUM>).