JP2013007673A - Sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor capable of being simply formed on a semiconductor substrate.SOLUTION: A sensor for detecting acceleration or pressure comprises: a first semiconductor element that is imparted with the acceleration or the pressure and outputs a voltage or a current of a frequency corresponding to the acceleration or the pressure; and a detecting section for generating a sensor value corresponding to the acceleration or the pressure on the basis of an output of the first semiconductor element. The first semiconductor element includes: a first acoustic wave propagating layer formed on a semiconductor substrate; a first acoustic wave reflecting layer formed such that an acoustic wave is confined in the first acoustic wave propagating layer; and a first contact that is formed on the first acoustic wave propagating layer and is connected to the detecting section.

Description

  Embodiments described herein relate generally to a sensor.

  As a pressure sensor and an acceleration sensor that can be formed on a semiconductor integrated circuit, a device having a MEMS (Micro Electro Mechanical System) structure is often used. Although MEMS can be formed on a silicon substrate, it is difficult to form it by a normal complementary metal oxide semiconductor (CMOS) process, which is unsuitable for further high integration.

JP 2011-58819 A

John J. Hall, “Electronic Effects in the Elastic Constants of n-Type Silicon”, Physical Review, Volume 161, No. 3, Sept. 1967, pp161

  Provided is a sensor that can be easily formed on a semiconductor substrate.

  According to the embodiment, the sensor that detects acceleration or pressure is supplied with the acceleration or pressure, and outputs a voltage or current having a frequency corresponding to the acceleration or pressure, and the first semiconductor. A detection unit that generates a sensor value corresponding to the acceleration or pressure based on the output of the element. The first semiconductor element includes a first acoustic wave propagation layer formed on a semiconductor substrate, a first acoustic wave reflection layer formed so as to confine the acoustic wave in the first acoustic wave propagation layer, and And a first contact formed on the first acoustic wave propagation layer and connected to the detection unit.

2 is a top view of the semiconductor element 100. FIG. 1 is a perspective view of a semiconductor element 100. FIG. 1 is a cross-sectional view of a semiconductor element 100. FIG. 1 is a block diagram showing a schematic configuration of a sensor 50 according to a first embodiment. FIG. 2 is a block diagram showing a schematic configuration of a sensor 51. FIG. 3 is a block diagram showing a schematic configuration of a sensor 52. The block diagram which shows schematic structure of the sensor 53 which concerns on 2nd Embodiment. The block diagram which shows schematic structure of the sensor 54 which concerns on 3rd Embodiment. The perspective view of the semiconductor element 150 used for the sensor which concerns on 4th Embodiment. The block diagram which shows schematic structure of the sensor 55 which concerns on 4th Embodiment. The top view of semiconductor element 100a, 100b used by 5th Embodiment. The block diagram which shows schematic structure of the sensor 56 which concerns on 5th Embodiment. The block diagram which shows schematic structure of the sensor 57 which concerns on 6th Embodiment.

  Hereinafter, embodiments will be specifically described with reference to the drawings.

(First embodiment)
1 to 3 are a top view, a perspective view, and a cross-sectional view, respectively, of a semiconductor element 100 used for a sensor. The semiconductor element 100 includes a silicon substrate (semiconductor substrate) 10, a p-type diffusion layer (acoustic wave propagation layer) 1, a SiO ₂ film (acoustic wave reflection layer) 2, an n-well 3, a contact 4, and a wiring 5. And.

  On the surface of the silicon substrate 10, for example, an n-well 3 doped with phosphorus or arsenic as an impurity is formed. A p-type diffusion layer 1 doped with, for example, boron as an impurity is formed inside the n-well 3. The shape of the p-type diffusion layer 1 as viewed from above is a substantially rectangular shape having a short side and a long side.

A groove 6 is formed in the silicon substrate 10 so as to surround the p-type diffusion layer 1 inside the n-well 3, and the SiO ₂ film 2 is embedded therein. The SiO ₂ film 2 has a so-called STI (Shallow Trench Isolation) structure, and electrically isolates the p-type diffusion layer 1 from other elements formed on the silicon substrate 10. The contact 4 is formed on the p-type diffusion layer 1 and electrically connects the p-type diffusion layer 1 and the wiring 5. The wiring 5 is connected to other elements (not shown).

  Since the semiconductor element 100 of FIGS. 1 to 3 has a simple structure, it can be formed by a normal CMOS process.

Generally, in a semiconductor having carriers, it is known that the volume changes when the charge density changes, and the charge density changes when the volume changes, that is, the interaction between electricity and mechanical vibration. More specifically, the following equation (1) is established, where ρ is a charge density, Φ is a variable proportional to the volume change, and c is the speed of sound in the semiconductor.

  The left side of the above equation (1) is an equation representing the propagation of acoustic waves. When there is a change in the charge density ρ (right side), it indicates that an acoustic wave of sound velocity c propagates (left side).

This applies to the semiconductor device 100 of FIGS. In the semiconductor element 100, holes exist as carriers in the p-type diffusion layer 1. When electric input is applied from the contact 4, the charge density of the p-type diffusion layer 1 changes, and as a result, the p-type diffusion layer 1 becomes an acoustic wave propagation layer and an acoustic wave propagates. On the other hand, the SiO ₂ film 2 functions as an acoustic wave reflection layer. That is, the acoustic wave is reflected at the interface between the p-type diffusion layer 1 and the SiO ₂ film 2, and an acoustic standing wave is generated in the p-type diffusion layer 1. The frequency of the acoustic standing wave is determined according to the length of the long side of the p-type diffusion layer 1 and the sound velocity c in the p-type diffusion layer 1.

  It is known that the speed of sound c varies with acceleration or pressure (hereinafter collectively referred to as external force). For example, when the external force changes, the sound speed c also changes due to the deformation potential effect.

  Therefore, the external force can be detected based on the frequency of the acoustic standing wave.

  1 to 3 shows an example having one contact 4, the semiconductor element 100 is formed on the other end side in addition to the contact 4 a formed on one end side of the p-type diffusion layer 1. You may have the contact 4b (not shown).

  FIG. 4 is a block diagram illustrating a schematic configuration of the sensor 50 according to the first embodiment. The sensor 50 includes a semiconductor element 100 and a detection unit 200. The contact 4 of the semiconductor element 100 is connected to the input terminal of the detection unit 200. When an external force P is applied to the semiconductor element 100, the semiconductor element 100 outputs a voltage V (P) or a current I (P) whose frequency depends on the external force P from the contact 4. Based on this, the detection unit 200 generates a sensor value corresponding to the external force P.

  Since the detection unit 200 amplifies the electric signal, it can be formed on the same silicon substrate as the semiconductor element 100, and the sensor 50 can be downsized. Hereinafter, a specific configuration example of the sensor 50 will be described.

  FIG. 5 is a block diagram illustrating a schematic configuration of the sensor 51. The detection unit 201 in FIG. 1 includes an amplifier 21 and a counter 22. The contact 4 of the semiconductor element 100 is connected to the input terminal and the output terminal of the amplifier 21. The amplifier 21 amplifies the output of the semiconductor element 100 and inputs it to the semiconductor element 100 again, so that the semiconductor element 100 resonates.

  Here, since the sound velocity c in the semiconductor element 100 depends on the external force P as described above, the resonance frequency also depends on the external force P. In this way, the amplifier 21 generates an oscillation signal that oscillates at a frequency f (P) that depends on the external force P. The counter 22 counts the number of pulses of the oscillation signal based on a predetermined reference clock CLK. Since the count value is substantially proportional to the frequency f (P), this count value becomes a sensor value corresponding to the external force P.

  By counting the frequency f (P) for a sufficiently long time, for example, about 1 ms for the oscillation frequency of 100 MHz, the signal component is amplified and the noise component is canceled, so the S / N ratio is improved. To do.

  FIG. 6 is a block diagram showing a schematic configuration of the sensor 52 when the semiconductor element 100 is provided with two contacts. In the sensor 52 shown in the figure, one contact of the semiconductor element 100 is connected to the input terminal of the amplifier 21, and the other contact is connected to the output terminal of the amplifier 21. The amplifier 21 amplifies a signal output from one contact of the semiconductor element 100 and inputs it to the other contact of the semiconductor element 100. As a result, the semiconductor element 100 resonates. Other operations are the same as those in FIG. In the configuration of FIG. 6, the restriction of connecting one contact of the device 100 to the ground terminal GND can be eliminated.

  Thus, in the first embodiment, a voltage or current whose frequency depends on the external force P is generated using the semiconductor element 100 having a simple structure. Therefore, the sensor can be formed on the semiconductor substrate without using a special process, and the external force P can be detected. Further, the sensors 51 and 52 can easily generate a sensor value by amplifying the output of the semiconductor element 100 and generating an oscillation signal having a frequency f (P) depending on the external force P.

The structure of the semiconductor element 100 is not limited to FIGS. In order to efficiently confine the acoustic wave in the p-type diffusion layer 1, it is desirable to provide an acoustic wave reflection layer so as to surround the acoustic wave propagation layer as shown in FIGS. The acoustic wave reflection layer should just be formed in the both ends of the long side direction of an area | region. For example, the SiO ₂ film 2 may be formed only at both ends of the p-type diffusion layer 1 in the long side direction, and the n well 3 may be formed on the side surface in the short side direction. The material of the acoustic wave reflection layer is desirably larger in difference with the acoustic impedance of the material of the silicon substrate 10 on which the p-type diffusion layer 1 is formed, and may be SiN, for example. 1 to 3 has the n well 3 and the p-type diffusion layer 1 formed therein, but the conductivity type is reversed to form the p well 3 'and the n-type diffusion layer 1'. Also good.

(Second Embodiment)
In the second embodiment described below, the external force P is detected with higher accuracy using two semiconductor elements 100.

  FIG. 7 is a block diagram illustrating a schematic configuration of the sensor 53 according to the second embodiment. In FIG. 7, the same components as those in FIG. 5 are denoted by the same reference numerals, and different points will be mainly described below.

  The sensor 53 includes a semiconductor element 100b, an amplifier 21b, and a counter 22b in addition to the sensor 51 of FIG. The detection unit 203 of the sensor 53 includes an amplifier 21 a, a counter 22 a, and a comparator (CMP) 23. The sensor 53 is preferably formed on the same silicon substrate 10.

  The semiconductor element 100b, the amplifier 21b, and the counter 22b have the same configuration as the semiconductor element 100a, the amplifier 21a, and the counter 22a, respectively. However, an external force P to be detected is applied to the semiconductor element 100a, and a constant reference external force P0 is applied to the semiconductor element 100b. The comparator 23 compares the count value of the counter 22a with the count value of the counter 22b.

  The operating characteristics of the semiconductor elements 100a and 100b, the amplifiers 21a and 21b, and the counters 22a and 22b in the sensor 53 may fluctuate due to changes in external factors that are not related to the external force P, such as temperature and power supply voltage. For this reason, when the sensor value changes, it cannot be distinguished whether the external force P has changed or other external factors have changed, and the accuracy of the sensor is reduced.

  Therefore, in this embodiment, the comparator 23 is provided, and the resonance frequency f (0) based on the semiconductor element 100a to which the external force P to be detected is applied and the resonance frequency f (P0) based on the semiconductor element 100b to which the reference external force P0 is applied. ) To cancel the change of the external factor and detect the external force P. More specifically, the following is performed.

  As a premise, the semiconductor element 100a and the semiconductor element 100b, the amplifier 21a and the amplifier 21b, and the counter 22a and the counter 22b are formed so that their operating characteristics fluctuate similarly in response to changes in external factors other than the external force P. Then, a known and constant reference external force P0 is applied to the semiconductor element 100b so that the external force P is not affected. For this purpose, the semiconductor element 100b may be formed at a position that is not affected by the external force P as much as possible, or the semiconductor element 100b may be formed so that even if the external force P is received, the change in the sound speed c is small.

  The reference frequency f (P0) of the reference oscillation signal generated by the amplifier 21b depends on external factors other than the external force P and the reference external force P0, but does not depend on the external force P. Therefore, the count value generated by the counter 22b also depends on external factors other than the external force P and the reference external force P0, but does not depend on the external force P.

  On the other hand, the amplifier 21a generates an oscillation frequency of the frequency f (P) as in the first embodiment. The frequency f (P) depends on external factors other than the external force P and the external force P. Therefore, the count value generated by the counter 22a also depends on external factors other than the external force P and the external force P.

  Then, the comparator 23 compares the counter value of the counter 22a with the counter value of the counter 22b. By taking the difference between the two, the influence of external factors other than the external force P is canceled, and a comparison result depending on the difference between the external force P and the reference external force P0 is obtained. This comparison result is a sensor value corresponding to the external force P.

  Thus, in the second embodiment, the comparison is performed by providing the semiconductor element 100b to which a constant reference external force P0 is applied. Therefore, fluctuations in the operation characteristics of each element due to changes in external factors other than the external force P can be canceled, and the accuracy of the sensor is improved.

  Note that a temperature compensation circuit using a heater and a thermometer may be mounted around the sensor 53 to further improve accuracy.

(Third embodiment)
In the above-described second embodiment, two amplifiers and two counters are used. However, in the third embodiment described below, these are provided one by one.

  FIG. 8 is a block diagram illustrating a schematic configuration of the sensor 54 according to the third embodiment. In FIG. 8, the same components as those in FIG. 7 are denoted by the same reference numerals, and the differences will be mainly described below.

  The sensor 54 includes semiconductor elements 100 a and 100 b, a detection unit 204 having one amplifier 21, a counter 22, and a comparator 23, and a switch 300. The switch 300 connects one of the semiconductor elements 100 a and 100 b to the amplifier 21.

  In the second embodiment, it is necessary to form the amplifiers 21a and 21b so that the operating characteristics similarly change with respect to external factors other than the external force P. However, in this embodiment, only one amplifier 21 is used. no need to do that.

  In the present embodiment, so-called CDS (Co-related Double Sampling) technology is applied, and the amplifier 21 and the counter 22 are used in a time-sharing manner with the timing shifted. That is, in one period, the amplifier 21 and the semiconductor element 100b are connected by the switch 300 to generate a count value based on the reference external force P0, and in another period, the amplifier 21 and the semiconductor element 100a are connected and detected by the switch 300. A count value based on the power external force P is generated. Then, the comparator 23 compares the two to generate a sensor value corresponding to the difference between the external force P and the reference external force P0.

  The frequency for switching the switch 300 is sufficiently longer than the frequencies f (P) and f (P0). For example, if the resonance frequency is 100 MHz, the frequency for switching the switch 300 is set to about several kHz.

  As described above, in the third embodiment, since the amplifier 21 and the counter 22 are used one by one in a time division manner, the circuit area can be reduced. In addition, since only one amplifier 21 is used, the operational characteristics of the amplifier 21 work in the same way for both count values, further improving the accuracy of the sensor.

(Fourth embodiment)
In the fourth embodiment, an angular velocity that is a kind of acceleration is detected as an external force.

  FIG. 9 is a perspective view of a semiconductor element 150 used in the sensor according to the fourth embodiment. Hereinafter, the difference from FIGS. 1 to 3 will be mainly described.

The semiconductor element 150 includes contacts 4 i 1, 4 i 2, 4 o 1, 4 o 2 formed on the p-type diffusion layer 1 surrounded by the SiO ₂ film 2. The contacts 4i1 and 4i2 have a rectangular shape extending in the vertical direction and are formed to face each other in the horizontal direction. On the other hand, the contacts 4o1 and 4o2 have a rectangular shape extending in the horizontal direction and are formed to face each other in the vertical direction. A line connecting the centers of the contacts 4i1 and 4i2 is orthogonal to a line connecting the centers of the contacts 4o1 and 4o2.

  In this embodiment, the p-type diffusion layer 1 has the same length in the horizontal direction and the vertical direction. Therefore, the semiconductor element 150 has substantially the same configuration as the semiconductor element 100, but an acoustic standing wave can be generated not only in the horizontal direction but also in the vertical direction of the semiconductor element 150.

  The semiconductor element 150 also has a simple configuration and can be formed by a normal CMOS process.

In the present embodiment, the angular velocity ω is detected using the semiconductor element 150 as follows. First, an acoustic standing wave is excited in the horizontal direction of the semiconductor element 150. For this purpose, the resonance phenomenon of the semiconductor element 150 may be used, or a periodic electrical signal such as a sine wave or a rectangular wave may be input to the contacts 4i1 and 4i2 from the outside. Due to this acoustic standing wave, a potential difference Vin is generated between the contacts 4i1 and 4i2. The frequency of the potential difference Vin is a frequency f determined by the shape of the semiconductor element 150 or the frequency of the electric signal. When the amplitude of the potential difference Vin is Ain, the potential difference Vin is expressed by the following equation (2).
Vin = Ain * sin2πft (2)

Here, when the angular velocity ω is given to the semiconductor element 150, Coriolis force is generated. The direction is a direction orthogonal to the acoustic standing wave, that is, a vertical direction. Therefore, a potential difference Vout is generated between the contacts 4o1 and 4o2. The frequency of this potential difference Vout is equal to the resonance frequency f of the semiconductor element 150. If the amplitude of the potential difference Vout is Aout, the potential difference Vout is expressed by the following equation (3).
Vout = Aout * sin2πft (3)

  Here, the amplitude Aout is proportional to the angular velocity ω. Therefore, the angular velocity ω can be known by detecting the amplitude Aout.

  FIG. 10 is a block diagram illustrating a schematic configuration of a sensor 55 according to the fourth embodiment. The sensor 55 includes a semiconductor element 150 and a detection unit 205 having the amplifier 21 and the mixer 24.

The amplifier 21 generates a potential difference Vin between the contacts 4i1 and 4i2. The mixer 24 multiplies the potential difference Vin and the potential difference Vout. The output OUT of the mixer 24 is expressed by the following equation (4).
OUT = Vin * Vout = (Ain * sin2πft) * (Aout * sin2πft)
= Ain * Aout / 2 * (1-cos4πft) (4)

  Therefore, the DC component of the output OUT is proportional to the amplitude Aout. Since the amplitude Aout is proportional to the angular velocity ω, the DC component of the output OUT becomes a sensor value corresponding to the angular velocity ω.

  If the shape of the p-type diffusion layer 1 of the semiconductor element 150 is a square having the same length in the vertical direction and the length in the horizontal direction, the potential difference Vout due to the Coriolis force can be extracted efficiently, and the amplitude Aout increases. The accuracy of the sensor is improved.

  Thus, in the fourth embodiment, the angular velocity can be detected using the semiconductor element 150 having a simple structure.

(Fifth embodiment)
In the fifth embodiment, the accuracy of a sensor is improved by using two semiconductor elements having different shapes.

  FIG. 11 is a top view of the semiconductor elements 100a and 100b used in the fifth embodiment. Since the structure is the same as that of FIG.

  Since the semiconductor elements 100a and 100b have the same length in the long side direction (horizontal direction) of the p-type diffusion layers 1a and 1b, the resonant frequencies of the excited acoustic standing waves are equal. As the external force P increases, the amplitude of the acoustic standing wave increases. However, since the lengths of the p-type diffusion layers 1a and 1b in the short side direction are different, the voltage that is output even when the same external force P is applied. Or the amplitude of the current is different. Therefore, the amplitude of the acoustic standing wave excited by the semiconductor element 100a is different from the amplitude of the acoustic standing wave excited by the semiconductor element 100a.

  More specifically, since the p-type diffusion layer 1b has a relatively short length w2 in the short side direction, an acoustic standing wave hardly occurs even when an external force P is applied, and the amplitude is small. On the other hand, since the p-type diffusion layer 1a has a relatively short length w1 in the short side direction, the amplitude of the acoustic standing wave excited when the same external force P is applied is large.

  In the present embodiment, the external force P is detected by utilizing the fact that the amplitude of the acoustic standing wave differs according to the external force P. Furthermore, the influence of an external factor is canceled using the p-type diffusion layers 1a and 1b having different shapes.

  FIG. 12 is a block diagram illustrating a schematic configuration of the sensor 56 according to the fifth embodiment. The sensor 56 includes semiconductor devices 100a and 100b having different shapes shown in FIG. 11, a detection unit 206 having an amplifier 21a and a comparator 25, and an amplifier 21b.

  The semiconductor device 100a, 100b is given an external force P to be detected.

The amplifier 21a amplifies the output of the semiconductor device 100a and generates a first oscillation signal. On the other hand, the amplifier 21b amplifies the output of the semiconductor device 100b and generates a second oscillation signal. As described above, since the resonance frequencies of the acoustic standing waves are equal in both the semiconductor devices 100a and 100b, the frequencies of the first and second oscillation signals are equal. However, the amplitude A ₁ (P) of the first oscillation signal is different from the amplitude A ₂ (P) of the _second oscillation signal.

The comparator 25 compares the amplitude A ₁ (P) with the amplitude A ₂ (P) and obtains a difference. Since the difference between the two also depends on the external force P, this difference becomes a sensor value corresponding to the external force P.

  As described in the second embodiment, the operation characteristics of the sensor may fluctuate due to changes in external factors other than the external force P. However, since the operating characteristics of the semiconductor elements 100a and 100b similarly change with respect to changes in external factors other than the external force P, the comparator 25 performs comparison to obtain a difference, thereby operating characteristics due to changes in external factors. Fluctuations can be canceled and the accuracy of the sensor is improved. In the present embodiment, it is not necessary to apply a constant reference external force P0.

  Thus, in the fifth embodiment, a plurality of semiconductor elements having different shapes are provided, and the amplitudes of the oscillation signals based on the outputs of both are compared, so that the accuracy of the sensor is improved.

(Sixth embodiment)
The sixth embodiment is a modification of the fifth embodiment, and the semiconductor elements 100a and 100b in FIG. 11 are common, but the sensor configuration is different. Hereinafter, the difference from the fifth embodiment will be mainly described.

  FIG. 13 is a block diagram showing a schematic configuration of a sensor 57 according to the sixth embodiment. The sensor 57 includes semiconductor devices 100a and 100b having different shapes shown in FIG. 11, a detection unit 207 having an amplifier 21a and a comparator 26, and an amplifier 21b.

  The amplifiers 21a and 21b each have an amplitude control terminal. Amplitude control signals CNTa and CNTb are input to the amplitude control terminals of the amplifiers 21a and 21b, respectively, and the amplitude of the oscillation signal can be controlled accordingly. More specifically, the amplitude of the oscillation signal can be increased as the amount of current flowing into the amplifiers 21a and 21b by the amplitude control signals CNTa and CNTb is increased.

In the present embodiment, the amplitude of the first oscillation signal generated by amplifying the output of the semiconductor element 100a and the amplitude of the second oscillation signal generated by amplifying the output of the semiconductor element 100b are both in advance. constant amplitude _{a 0} which defines the amplitude control signal CNTa, sets the CNTb. For example, the amplitude of the first and second oscillation signal is feedback controlled so as to approach the constant amplitude A _0, it is possible to set the amplitude control signal CNTa, the CNTb automatically.

As described above, the amplitude of the acoustic standing wave excited by the semiconductor elements 100a and 100b depends on the external force P. Thus, the amplitude control signal CNTa for the amplitude of the first and second oscillation signal to a constant amplitude _{A 0,} CNTb also depends on the external force P.

That is, since the amplitude of the acoustic standing wave excited in the semiconductor device 100a is large, the amplitude control signal CNTa can be not so large an amplitude of the first oscillation signal constant amplitude A _0. Meanwhile, since the amplitude of the acoustic standing wave excited in the semiconductor device 100b is small, in order to the amplitude of the second oscillation signal to a constant amplitude A _0, it is necessary to increase the amplitude control signal CNTb some extent.

  The comparator 26 compares the amplitude control signal CNTa and the amplitude control signal CNTb and takes a difference. Since the difference between the two also depends on the external force P, this difference becomes a sensor value corresponding to the external force P. By taking the difference, it is possible to cancel the fluctuation of the operating characteristics due to the change of the external factor, and the accuracy of the sensor is improved. In this embodiment, it is not necessary to apply a constant reference external force P0.

  As described above, in the sixth embodiment, a plurality of semiconductor elements having different shapes are provided, and the amplitude control signal for making the amplitude of the oscillation signal based on the outputs of the two constants is compared, so that the accuracy of the sensor is improved. To do.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

1, 1a, 1b p-type diffusion layer 2 SiO ₂ film 3 n well 4, 4i1, 4i2, 4o1, 4o2, 4a, 4b contact 5 wiring 10 silicon substrate 21, 21a, 21b amplifier 22, 22a, 22b counter 23, 25 , 26 Comparator 24 Mixer 50-57 Sensor 100, 100a, 100b, 150 Semiconductor element 200-207 Detector 300 Switch

Claims (9)

A sensor for detecting acceleration or pressure,
A first semiconductor element which receives the acceleration or pressure and outputs a voltage or current having a frequency corresponding to the acceleration or pressure;
A detection unit that generates a sensor value corresponding to the acceleration or pressure based on the output of the first semiconductor element;
The first semiconductor element is:
A first acoustic wave propagation layer formed on a semiconductor substrate;
A first acoustic wave reflection layer formed to confine an acoustic wave in the first acoustic wave propagation layer;
A sensor comprising: a first contact formed on the first acoustic wave propagation layer and connected to the detection unit. The detector is
A first amplifier for amplifying an output of the first semiconductor element and generating a first oscillation signal having a frequency corresponding to the acceleration or pressure;
The sensor according to claim 1, further comprising: a first counter that counts the number of pulses of the first oscillation signal and generates a first count value corresponding to the acceleration or pressure. A second semiconductor element which is supplied with a constant reference acceleration or a reference pressure and outputs a voltage or a current having a frequency corresponding to the reference acceleration or the reference pressure;
A second amplifier for amplifying an output of the second semiconductor element and generating a second oscillation signal having a frequency corresponding to the reference acceleration or the reference pressure;
A second counter that counts the number of pulses of the second oscillation signal and generates a second count value corresponding to the reference acceleration or the reference pressure,
The detection unit includes a comparator that compares the first count value with the second count value and generates a comparison result according to the acceleration or pressure,
The second semiconductor element is:
A second acoustic wave propagation layer formed on the semiconductor substrate;
A second acoustic wave reflection layer formed to confine an acoustic wave in the second acoustic wave propagation layer;
The sensor according to claim 2, further comprising: a second contact formed in the second acoustic wave propagation layer and connected to the second amplifier. A second semiconductor element which is supplied with a constant reference acceleration or a reference pressure and outputs a voltage or a current having a frequency corresponding to the reference acceleration or the reference pressure;
A switch for supplying an output of the first semiconductor element or the second semiconductor element to the detection unit at a predetermined timing;
The first amplifier generates the first oscillation signal obtained by amplifying the output of the first semiconductor element or the second oscillation signal obtained by amplifying the output of the second semiconductor element at the predetermined timing,
The first counter generates the first count value obtained by counting the number of pulses of the first oscillation signal or the second count value obtained by counting the number of pulses of the second oscillation signal at the predetermined timing. And
The detection unit includes a comparator that compares the first count value with the second count value and generates a comparison result according to the acceleration or pressure,
The second semiconductor element is:
A second acoustic wave propagation layer formed on the semiconductor substrate;
A second acoustic wave reflection layer formed to confine an acoustic wave in the second acoustic wave propagation layer;
The sensor according to claim 2, further comprising: a second contact formed in the second acoustic wave propagation layer and connected to the first amplifier via the switch. A second semiconductor element that is supplied with the acceleration or pressure, and that outputs a voltage or current having the same frequency and different amplitude as the voltage or current output from the first semiconductor element in accordance with the acceleration or pressure; ,
A second amplifier that amplifies the output of the second semiconductor element and generates a second oscillation signal having a second amplitude according to the acceleration or pressure;
The detector is
A first amplifier for amplifying an output of the first semiconductor element and generating a first oscillation signal having a first amplitude according to the acceleration or pressure;
A comparator that compares the first amplitude with the second amplitude and generates a comparison result according to the acceleration or pressure;
The second semiconductor element is:
A second acoustic wave propagation layer formed on the semiconductor substrate;
A second acoustic wave reflection layer formed to confine an acoustic wave in the second acoustic wave propagation layer;
The sensor according to claim 1, further comprising: a second contact formed in the second acoustic wave propagation layer and connected to the second amplifier. A second semiconductor element that is supplied with the acceleration or pressure, and that outputs a voltage or current having the same frequency and different amplitude as the voltage or current output from the first semiconductor element in accordance with the acceleration or pressure; ,
A second detection unit that amplifies the output of the second semiconductor element and generates a second oscillation signal having a predetermined amplitude based on a second amplitude control signal;
The detector is
A first detector for amplifying an output of the first semiconductor element and generating a first oscillation signal having an amplitude determined in advance based on a first amplitude control signal;
A comparator that compares the first amplitude control signal with the second amplitude control signal and generates a comparison result according to the acceleration or pressure;
The second semiconductor element is:
A second acoustic wave propagation layer formed on the semiconductor substrate;
A second acoustic wave reflection layer formed to confine an acoustic wave in the second acoustic wave propagation layer;
The sensor according to claim 1, further comprising: a second contact formed in the second acoustic wave propagation layer and connected to the second amplifier. The first semiconductor element is:
A second contact formed on the first acoustic wave propagating layer so as to face the first contact in a first direction;
The first acoustic wave propagation layer has third and fourth contacts formed opposite to each other in a second direction substantially orthogonal to the first direction,
The detector is
An amplifier for generating a first potential difference between the first and second contacts;
A mixer that generates a sensor value corresponding to the acceleration based on the first potential difference and a second potential difference that occurs between the third and fourth contacts and whose amplitude corresponds to the acceleration; The sensor according to claim 1, comprising:   The sensor according to claim 7, wherein the first acoustic wave propagation layer has a substantially square shape.   The sensor according to claim 1, wherein the detection unit is formed on the semiconductor substrate.

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