JP4743226B2 - Semiconductor dynamic quantity sensor - Google Patents

Description

  The present invention relates to a semiconductor dynamic quantity sensor.

  Patent Document 1 discloses a sensor that detects acceleration acting in a direction perpendicular to the surface of a substrate.

  FIG. 27 shows a capacitive acceleration sensor using the SOI substrate described in Patent Document 1. On the support substrate 100, a movable electrode portion (weight portion) 102 is connected and supported by beams 101a, 101b, 101c, and 101d. The beams 101a, 101b, 101c, and 101d have a bowl shape, and the movable electrode portion 102 is displaced in the Z-axis direction perpendicular to the surface of the substrate. The acceleration is detected from a change in capacitance between the support substrate 100 and the movable electrode unit 102.

This sensor uses an SOI substrate (wafer), and after patterning a thin film silicon layer into a desired shape in an anisotropic dry etching process, the buried oxide film is removed with hydrofluoric acid (HF) to form a movable region. It is formed by etching.
JP-A-9-113534

  In order to detect acceleration, it is necessary to connect the movable electrode portion (weight portion) 102 and the support substrate 100. However, in the case of the SOI structure, there is a drawback that the number of steps for connecting to the support substrate 100 increases. Specifically, it is necessary to provide the pad 110 on the support substrate 100 and perform wire bonding to the pad 110.

  The present invention has been made paying attention to the above-mentioned problems, and the object thereof is to configure a semiconductor dynamic quantity sensor using a laminated substrate in which a thin film semiconductor layer is disposed on a support substrate via an insulating film. An object of the present invention is to provide a semiconductor dynamic quantity sensor capable of simplifying a wiring line.

According to the first aspect of the present invention, there is provided an SOI structure laminated substrate in which an insulating film is arranged on one side surface of a supporting substrate made of a semiconductor material and in which a potential is floating, and a thin film semiconductor layer is arranged on the insulating film. The first beam structure is defined in the thin film semiconductor layer, and the movable electrode portion of the first beam structure is disposed to face the support substrate, which is a common fixed electrode, with a gap therebetween. While the first carrier wave signal generated in synchronization with the clock signal is applied to the part, the movable electrode part is displaced in the direction perpendicular to the surface of the support substrate, which is a common fixed electrode, by the action of the mechanical quantity, and the movable electrode The first capacitor component (E1) in which the capacitance between the first substrate and the support substrate changes, and the first capacitor component (E1) together with the multilayer substrate are integrated into one chip, and the second beam structure in the thin film semiconductor layer body A first carrier wave that is formed in a divided manner and is arranged so that the movable electrode portion of the second beam structure is opposed to the support substrate, which is a common fixed electrode, via a gap, and is generated in synchronization with the clock signal on the movable electrode portion. While the second carrier wave signal having a phase opposite to that of the signal is applied, the movable electrode portion is displaced in a direction perpendicular to the surface of the support substrate, which is a common fixed electrode, by the action of the mechanical quantity, and the movable electrode portion and the support substrate The third capacitor component (E3) in which the capacitance between the first and third capacitor components changes in a state different from the capacitance due to the displacement of the movable electrode portion of the first beam structure, and the first and third capacitor components (E1, E3) is formed into a single chip on the laminated substrate, and the signal extraction counter electrode portion is defined in the thin film semiconductor layer with the insulating film below it, and the signal extraction counter electrode portion is the first and third capacitors. Fixed power of components A second capacitor component (E2) disposed opposite to the support substrate, and a switched capacitor circuit electrically connected to the counter electrode portion for signal extraction. and detecting a capacitance difference caused between the first capacitor forming portion by respective movable electrode portion is displaced (E1) and the third capacitor components (E3) by the action of a physical quantity at the time, the switch The capacitor circuit includes an operational amplifier, a feedback capacitor, and a switching element. A signal from the counter electrode portion for signal extraction is input to the inverting input terminal of the operational amplifier, and a first inverting input terminal of the operational amplifier is connected to the first operational amplifier. When the capacitance C1 of the capacitor component (E1) and the capacitance C3 of the third capacitor component (E3) are equal, the voltage level appearing at the counter electrode for signal extraction is input. The switch element is a switched capacitor circuit in which a first carrier wave signal rises and a second carrier wave signal turns on for a certain period of time by a trigger signal generated in synchronization with a clock signal. In the operation, a voltage Vcc is applied to the movable electrode portion of the first beam structure by the first carrier wave signal, and a voltage of 0 volt is applied to the movable electrode portion of the second beam structure by the second carrier wave signal. The timing at which the switch element is turned on and the output voltage Vo from the switched capacitor circuit becomes Vcc / 2, the timing T2 at which a predetermined time elapses from the timing T1 and the switch element is turned off, and the timing T2, The first carrier signal and the second carrier signal are switched, and the output voltage Vo is changed to the capacitance C1 of the first capacitor component (E1). It characterized by having a timing T3 that changes according to the difference the dynamic variation of the capacitance C3 of the capacitor components of the 3 (E3).

The invention described in claim 2 is characterized in that a silicon nitride film is formed in a portion of the support substrate facing the movable electrode portion of the second beam structure.

The invention described in claim 3 has a shield layer to which a constant voltage is applied surrounding the first beam structure, the second beam structure, and the signal extraction counter electrode portion.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.

  In this embodiment, the semiconductor acceleration sensor is embodied. FIG. 1 shows a plan view of a semiconductor acceleration sensor. FIG. 2 shows a longitudinal section taken along line AA in FIG. FIG. 3 shows a longitudinal section taken along line BB in FIG. This sensor is a sensor that detects acceleration applied in a direction perpendicular to the surface of the substrate (a direction perpendicular to the substrate).

  As shown in FIG. 2, an SOI substrate 1 is used as a sensor chip, and a thin film silicon layer (single crystal silicon layer) is formed on a support substrate 2 made of a single crystal silicon substrate via an insulating film 3 made of a silicon oxide film. ) 4 is arranged. In a broad sense, the SOI substrate 1 is a laminated substrate, the support substrate 2 is made of a semiconductor material, and the thin film silicon layer 4 is made of a thin film semiconductor layer. The thin film silicon layer 4 is formed by disposing a single crystal silicon substrate on the support substrate 2 with an insulating film 3 interposed therebetween and then reducing the film thickness. The laminated body of the support substrate 2 and the insulating film 3 has a square plate shape.

  The SOI substrate 1 constitutes a first capacitor component E1 and a second capacitor component E2 (one-chip configuration). Hereinafter, the first and second capacitor components E1 and E2 will be described.

  A through hole 5 is formed in the thin film silicon layer 4, and the thin film silicon layer 4 is partitioned and formed in a predetermined shape by the through hole 5. That is, as shown in FIG. 1, the through hole 5 partitions the beam structure 10, the signal extraction counter electrode portion 20, and the frame portion 40 around these members (10, 20). A first capacitor component E1 is configured using the beam structure 10, and a second capacitor component E2 is configured using the signal extraction counter electrode unit 20.

  The beam structure 10 includes anchor portions 11a, 11b, 11c, and 11d, beam portions 12a, 12b, 12c, and 12d, and a movable electrode portion (weight portion) 13. The anchor portions 11a, 11b, 11c, and 11d are fixed on the insulating film 3. The beam portions 12a, 12b, 12c, and 12d and the movable electrode portion (weight portion) 13 are disposed on the insulating film 3 with a gap 14 as shown in FIGS. That is, the beam portions 12a, 12b, 12c, and 12d extend from the anchor portions 11a, 11b, 11c, and 11d, and the movable electrode portion (weight portion) 13 is connected and supported at the distal ends of the beam portions 12a, 12b, 12c, and 12d. Yes. In this way, the four beam-shaped beams (12a, 12b, 12c, 12d) are provided, and the movable electrode portion (weight portion) 13 is supported by the beam portions 12a, 12b, 12c, 12d. Part) 13 is disposed opposite to the support substrate 2 with a gap 14 therebetween.

  Further, as shown in FIG. 1, the weight portion 13 is formed with a through hole 15 to reduce the weight. The movable electrode portion (weight portion) 13 is movable in a direction (vertical direction) orthogonal to the surface of the support substrate 2. A capacitance (capacitor capacitance) C1 is formed between the movable electrode portion (weight portion) 13 and the support substrate 2 as shown in FIG. That is, the movable electrode part (weight part) 13 and the support substrate 2 form a counter electrode, and the capacitor C1 is formed between the two counter electrodes.

  Here, the beam portions 12a to 12d displace the movable electrode portion (weight portion) 13 in the direction when receiving acceleration in a direction (vertical direction) orthogonal to the surface of the support substrate 2 and also disappear the acceleration. Accordingly, it has a spring function of restoring it to its original state.

  In FIG. 1, an electrode pad (aluminum pad) 16 for wire bonding is formed on the upper surface of an anchor portion 11c made of a thin film silicon layer.

  The counter electrode portion 20 for signal extraction shown in FIG. 1 includes a rectangular portion 21 and a strip-shaped portion 22, and the strip-shaped portion 22 for pad formation extends from the rectangular portion 21. As shown in FIG. 2, the signal extraction counter electrode portion 20 is partitioned with the insulating film 3 thereunder, and as shown in FIG. 4, the signal extraction counter electrode portion 20 is between the support substrate 2 and the signal extraction counter electrode portion 20. A capacitance (capacitor capacitance) C2 is formed. An electrode pad (aluminum pad) 23 for wire bonding is formed on the upper surface of the strip portion 22 made of the thin film silicon layer of FIG. Then, as shown in FIG. 4, the change in capacitance due to the displacement of the movable electrode portion 13 of the first capacitor component E <b> 1 is taken out from the signal extraction counter electrode portion 20 through the support substrate 2.

  Further, regarding the frame portion 40 around the beam structure 10 and the signal extraction counter electrode portion 20 in FIG. 1, wire bonding is performed on the upper surface of the thin film silicon layer 4 around the beam structure 10 and the signal extraction counter electrode portion 20. An electrode pad (aluminum pad) 41 is formed. The electrode pad (aluminum pad) 41 fixes the thin-film silicon layer 4 at the periphery of the beam structure 10 and the signal extraction counter electrode portion 20 to a constant potential, whereby the beam structure 10 and the signal extraction counter electrode portion 20 are fixed. Will be shielded.

  The semiconductor acceleration sensor (sensor chip) is manufactured as follows. The manufacturing process will be described with reference to FIG. FIG. 5 is a cross section taken along line BB in FIG.

  First, as shown in FIG. 5A, a wafer-like SOI substrate 1 is prepared. Then, electrode pads 16, 23, and 41 (see FIG. 1) are formed on the thin film silicon layer 4 by using a photolithography technique and an etching technique.

  Subsequently, as shown in FIG. 5B, the mask material 7 is patterned, and anisotropic dry etching is performed by a dry etching apparatus to form an insulating film (embedded oxide film) 3 on the thin film silicon layer 4. The reaching through hole 5 and the through hole 15 are formed (patterned). Furthermore, isotropic dry etching is performed from the surface side of the SOI substrate (wafer) 1 where the insulating film (buried oxide film) 3 is exposed with the mask material 7 left, as shown in FIG. As such, the portion of the thin film silicon layer 4 in contact with the insulating film (buried oxide film) 3 is removed. Thereby, the movable electrode portion (weight portion) 13 and the beam portions 12a, 12b, 12c, and 12d of the beam structure 10 become movable. Then, by removing the mask material 7 and dicing, the sensor chip shown in FIG. 1 and the like is completed.

  In the semiconductor acceleration sensor configured as described above, when an acceleration including a component in a direction (vertical direction) orthogonal to the surface of the substrate 2 is applied, the movable electrode portion (weight portion) 13 moves in the direction. It will be displaced. The amount of displacement corresponding to the acceleration is proportional to the mass of the movable electrode portion (weight portion) 13 and the restoring force of the beam portions 12a, 12b, 12c, and 12d. In this case, a capacitor C <b> 1 is formed between the movable electrode portion 13 and the support substrate 2. Further, as shown in FIG. 4, the potential of the support substrate 2 is in a floating state, and a change in capacitance appears on the substrate 2.

  FIG. 6 shows a circuit configuration of a capacitance change detection circuit (CV conversion circuit) for detecting the change in capacitance as described above. However, in FIG. 6, the semiconductor acceleration sensor is represented by an equivalent circuit.

  A carrier wave signal (frequency; for example, 100 kHz, voltage level Vcc is, for example, 5 volts) composed of a rectangular wave as shown in FIG. 7 is applied to the electrode pad 16 in the beam structure 10. Although not specifically shown, the carrier signal is formed in synchronization with the clock signal from the oscillation circuit.

  In this way, in the first capacitor component E1, the movable electrode portion 13 is displaced in the direction perpendicular to the surface of the support substrate 2 by the action of acceleration while the carrier voltage is applied to the movable electrode portion 13, and the movable electrode portion The capacitance C1 between 13 and the support substrate 2 changes. At this time, the capacitor C1 is taken out from the support substrate 2.

  In FIG. 6, a switched capacitor circuit 50 as a CV conversion circuit is connected to the pad 23. The switched capacitor circuit 50 is formed on a chip different from the sensor chip shown in FIG. In the state in which the carrier wave signal is applied as described above, the potential level of the electrode pad 23 in the counter electrode portion 20 for signal extraction is a level corresponding to the capacitance C1, and the potential level is switched to the switched capacitor circuit. 50 is detected.

  Specifically, the switched capacitor circuit 50 is connected by combining an operational amplifier 51, a feedback capacitor 52, and a switch element 53 as illustrated. The operational amplifier 51 is configured such that a signal from the electrode pad 23 is input to the inverting input terminal and a voltage signal of Vcc is applied to the non-inverting input terminal. The switch element 53 is turned on / off by a trigger signal generated in synchronization with a clock signal from the oscillation circuit (not shown), and is constant at the rising timing of the carrier signal as shown in FIG. It is set to turn on only for a time (a time shorter than a half cycle of the carrier signal).

  The capacitance change detection circuit (CV conversion circuit) shown in FIG. 6 operates as follows.

  That is, at timing T1 in the timing chart of FIG. 7, a voltage of Vcc (for example, 5 volts) is applied to the electrodes in the beam structure 10. At this time, since the switch element 53 is turned on, the output voltage Vo from the switched capacitor circuit 50 becomes Vcc.

  When the switch element 53 is turned off at a timing T2 at which a predetermined time has elapsed from the timing T1, the voltage applied to the electrodes does not change, so the output voltage Vo remains at Vcc. Next, when the carrier voltage is switched, the applied voltage to each electrode changes.

  Here, since the level of the output voltage Vo changes according to the magnitude of the acceleration acting on the capacitor C1, that is, the electrode part (weight part) 13, the magnitude of the acceleration is obtained using the output voltage Vo. Can be detected.

That is, with respect to the capacitance C1 and the fixed capacitance C2 between the movable electrode and the fixed electrode, the output of the sensor when acceleration is applied is due to the change in the capacitance between the movable electrode and the fixed electrode, and the change in the capacitance between them. appear. Specifically, the sensor output voltage Vo is
Vo = C1 · C2 · Vcc / (C1 + C2) / Cf
It becomes. Where Cf is the feedback capacitance of the switched capacitor circuit.

Here, if the C1 value is sufficiently smaller than the C2 value, the sensor output voltage Vo is
Vo = C1 · Vcc / Cf
It becomes.

  Therefore, an output proportional to the capacitance C1 that changes with acceleration is obtained.

  As described above, the present embodiment has the following features.

  The first capacitor component E1 and the second capacitor component E2 are made into one chip using the SOI substrate 1, and the movable electrode portion 13 of the beam structure 10 in the first capacitor component E1 is accelerated. Due to the action, the capacitance between the movable electrode portion 13 and the support substrate 2 is changed by being displaced in a direction perpendicular to the surface of the support substrate 2. On the other hand, in the second capacitor component E2, the counter electrode portion 20 for signal extraction in the thin film silicon layer 4 is partitioned and formed with the insulating film 3 underneath. Then, a change in capacitance due to the displacement of the movable electrode portion 13 of the first capacitor component E1 is taken out from the signal extraction counter electrode portion 20. Therefore, since it is not necessary to connect to the support substrate 2 in order to detect acceleration, for example, an increase in the number of steps for connecting to the support substrate 2 is avoided. In this way, when a semiconductor acceleration sensor is configured using the SOI substrate 1, the potential of the support substrate 2 can be made floating to simplify the wiring line.

  Since the shield layer is formed by applying a constant voltage to a portion (frame portion 40) around the beam structure 10 and the signal extraction counter electrode portion 20 in the thin film silicon layer 4, it is resistant to noise.

  Next, another example will be described.

  As shown in FIGS. 8, 9, and 10, the entire outer periphery of the beam structure 10 in the thin film silicon layer 4 may be used as the signal extraction counter electrode portion 20. That is, the signal extraction counter electrode portion 20 may be formed around the beam structure 10 in the thin film silicon layer 4 in one chip.

  Also, a differential capacitance type semiconductor acceleration sensor shown in FIGS. In other words, the sensor shown in FIG. 1 includes the movable capacitor type first capacitor component E1 and the fixed capacitor type second capacitor component E2, but the sensor shown in FIGS. In addition to the first capacitor component E1 of the formula and the second capacitor component E2 of the fixed capacitance type, the third capacitor component E3 of the movable capacitance type is provided. And the difference of the capacity | capacitance in the 1st capacitor | condenser structure part E1 and the capacity | capacitance in the 3rd capacitor | condenser structure part E3 is detected.

  Hereinafter, this sensor will be described in detail.

  The SOI substrate 1 constitutes a first capacitor component E1, a second capacitor component E2, and a third capacitor component E3 (made in one chip). As shown in FIG. 11, the left and right first and second beam structures 10 and 30, the signal extraction counter electrode portion 20 disposed therebetween, and these members (through the through-hole 5 formed in the thin film silicon layer 4) 10, 20, 30) surrounding frame 40 is defined. A first capacitor component E1 is configured using the first beam structure 10, and a third capacitor component E3 is configured using the second beam structure 30. A second capacitor component E <b> 2 is configured using the electrode unit 20.

  The second beam structure 30 has the same structure as that of the first beam structure 10, and the second beam structure 30 includes anchor portions 31a, 31b, 31c, and 31d and beam portions 32a, 32b, 32c, and 32d. And a movable electrode part (weight part) 33. As shown in FIG. 12, the beam portions 32 a to 32 d and the movable electrode portion (weight portion) 33 are arranged on the insulating film 3 via the gap 34, and the movable electrode portion (weight portion) 33 is attached to the support substrate 2. On the other hand, they are arranged to face each other via a gap 34. Further, as shown in FIG. 11, a through hole 35 is formed in the movable electrode portion (weight portion) 33. A capacitance (capacitor capacitance) C3 is formed between the movable electrode portion (weight portion) 33 and the support substrate 2 as shown in FIG. That is, the movable electrode part (weight part) 33 and the support substrate 2 form a counter electrode, and a capacitor C3 is formed between the counter electrodes.

  As described above, the second beam structure 30 and the first beam structure 10 have the same structure, but the length L1 of the beam portion in the first beam structure 10 in FIG. In comparison with the length L2 of the beam portion in the beam structure 30, the length L2 is larger than the length L1. Thereby, when acceleration is applied, the electrode portion 33 of the second beam structure 30 is displaced more greatly than the electrode portion 13 of the first beam structure 10. In this way, the first beam structure 10 and the second beam structure 30 have different capacitance changes when acceleration is applied. As shown in FIG. 14, the difference (C1−C3) between the capacitance C1 in the first capacitor component E1 and the capacitance C3 in the third capacitor component E3 is the counter electrode portion for signal extraction from the support substrate 2. 20 will be taken out.

  In FIG. 11, an electrode pad (aluminum pad) 36 for wire bonding is formed on the upper surface of an anchor portion 31d made of a thin film silicon layer.

  As shown in FIG. 14, a capacitance (capacitor capacitance) C <b> 2 is formed between the counter electrode portion 20 for signal extraction in FIG. 11 and the support substrate 2.

  In the semiconductor acceleration sensor configured as described above, when an acceleration including a component in the direction (vertical direction) orthogonal to the surface of the substrate 2 is applied, the movable electrode portions (weight portions) 13 and 33 It will be displaced in the direction. The amount of displacement corresponding to the acceleration is proportional to the mass of the movable electrode portions (weight portions) 13 and 33 and the restoring force of the beam portions 12a to 12d and 32a to 32d. In this case, a first capacitor C 1 is formed between the movable electrode portion 13 and the support substrate 2, and a third capacitor C 3 is formed between the movable electrode portion 33 and the support substrate 2.

  In the present example, the first and third capacitors C1 and C3 are set to be equal to each other when no acceleration is applied. That is, in the beam structures 10 and 30 arranged on the left and right in FIG. 11, C1 = C3.

  FIG. 15 shows a circuit configuration of a capacitance change detection circuit (CV conversion circuit) for detecting the change in capacitance as described above. However, in FIG. 15, the semiconductor acceleration sensor is expressed by an equivalent circuit.

  A first carrier wave signal (frequency; for example, 100 kHz, voltage level Vcc is, for example, 5 volts) composed of a rectangular wave as shown in FIG. 16 is applied to the electrode pad 16 in the first beam structure 10. Further, the electrode pad 36 in the second beam structure 30 has a second carrier wave signal (frequency; for example, 100 kHz, voltage level Vcc is, for example, 5 volts) formed of a rectangular wave that is 180 ° out of phase with the first carrier wave signal. Is applied. Although not specifically shown, the first and second carrier signals are formed in synchronization with a clock signal from the same oscillation circuit.

  In this way, in the first capacitor component E1, the movable electrode portion 13 is displaced in the direction perpendicular to the surface of the support substrate 2 by the action of acceleration while the carrier voltage is applied to the movable electrode portion 13, and the movable electrode portion The capacitance C1 between 13 and the support substrate 2 changes. Similarly, in the third capacitor component E3, the movable electrode portion 33 is displaced in the direction perpendicular to the surface of the support substrate 2 by the action of acceleration while the carrier voltage of the reverse phase is applied to the movable electrode portion 33, and the movable electrode portion 33 moves. The capacitance C3 between the portion 33 and the support substrate 2 changes. At this time, the capacitance C3 between the movable electrode portion 33 and the support substrate 2 changes in a state different from the capacitance C1 due to the displacement of the movable electrode portion 13 of the first beam structure 10, and the capacitance difference (C1− C3) is removed from the support substrate 2.

  In FIG. 15, a switched capacitor circuit 50 as a CV conversion circuit is connected to the pad 23. In the state where each carrier wave signal is applied as described above, the potential level of the electrode pad 23 in the counter electrode portion 20 for signal extraction becomes a level corresponding to the first and third capacitors C1 and C3. The potential level is detected by the switched capacitor circuit 50.

  Specifically, in the operational amplifier 51, a signal from the electrode pad 23 is input to the inverting input terminal, and Vcc / 2 (that is, the first and third capacitors C1, C3 are equal to the non-inverting input terminal) The voltage signal is equivalent to the potential level that appears. The switch element 53 is turned on / off by a trigger signal generated in synchronization with a clock signal from the oscillation circuit (not shown). As shown in FIG. 16, the rising timing of the first carrier signal It is set to turn on only for a certain time (a time shorter than a half cycle of the first carrier signal) at the (falling timing of the second carrier signal).

  The capacitance change detection circuit (CV conversion circuit) shown in FIG. 15 operates as follows.

  That is, when the first and third capacitors C1 and C3 are equal, at the timing T1 in the timing chart of FIG. 16, Vcc (for example, 5 volts) is applied to the electrode of the first beam structure 10 and the second beam. A voltage of 0 volts is applied to the electrodes in the structure 30. At this time, since the switch element 53 is turned on, the output voltage Vo from the switched capacitor circuit 50 becomes Vcc / 2.

  When the switch element 53 is turned off at a timing T2 at which a predetermined time has elapsed from the timing T1, the applied voltage to each electrode does not change, so the output voltage Vo also remains at Vcc / 2. Next, when the carrier voltage is switched, the applied voltage to each electrode changes.

  Here, the level of the output voltage Vo changes in accordance with the differential change amount of the first and third capacitors C1 and C3, that is, the magnitude of acceleration acting on the electrode portions (weight portions) 13 and 33. Therefore, the magnitude of acceleration can be detected using the output voltage Vo.

That is, regarding the capacitances C1, C3 and the fixed capacitance C2 between the movable electrode and the fixed electrode, the output of the sensor when acceleration is applied changes the distance between the movable electrode and the fixed electrode, and changes in the capacitance (C1- Occurs when C3) occurs. Specifically, the sensor output voltage Vo is
Vo = C2 * (C1-C3) * Vcc / (C1 + C2 + C3) / Cf
It becomes. Where Cf is the feedback capacitance of the switched capacitor circuit.

Here, if the C1 and C3 values are sufficiently smaller than the C2 value, the sensor output voltage Vo is
Vo = (C1-C3) .Vcc / Cf
It becomes.

  Therefore, an output proportional to the capacitance difference (C1-C3) that changes with acceleration is obtained.

  In this way, the movable electrode portion 13 of the beam structure 10 in the first capacitor component E1 and the movable electrode portion 33 of the beam structure 30 in the third capacitor component E3 move in the same direction and are generated. The capacitance difference (C1-C3) is detected, and the capacitance difference (C1-C3) is taken out via the second capacitor component E2.

  1-3, the member disposed between the support substrate 2 and the thin film silicon layer 4, that is, the member disposed between the parallel plate electrodes is the lower electrode / silicon oxide film in FIGS. Although it is / air gap / upper electrode, it may be as follows.

  As shown in FIG. 17, the lower electrode / silicon oxide film / air gap / silicon oxide film / upper electrode may be used. Alternatively, as shown in FIG. 18, the lower electrode / air gap / silicon oxide film / upper electrode may be used. Alternatively, as shown in FIG. 19, the lower electrode / silicon oxide film / silicon nitride film / air gap / upper electrode may be used.

  In addition, as another method of giving a difference (C1−C3) between the capacitance C1 in the first capacitor configuration unit E1 and the capacitance C3 in the third capacitor configuration unit E3 in FIGS. Good. In other words, in FIG. 11, the capacity when acceleration is applied by changing the lengths L1 and L2 of the beam portions in the beam structures 10 and 30 is different (although the capacity change is different), Instead, it may be as follows.

  As shown in FIG. 20, the beam portion width W (W2> W1) in the beam structures 10 and 30 may be changed, thereby changing the spring constant k of the beam portions of the beam structures 10 and 30. .

  Alternatively, as shown in FIG. 21, the sizes of the movable electrode portions 13 and 33 in the beam structures 10 and 30 are made different (W11> W10), thereby changing the mass m of the movable electrode portions 13 and 33. May be. Alternatively, as shown in FIG. 22, the vertical and horizontal dimensions of the movable electrode portions 13 and 33 in the beam structures 10 and 30 are the same, and the through-hole 15 in the beam structure 10 and the through-hole 35 in the beam structure 30 Although the size is the same, a larger through hole 60 is formed in the beam structure 30. Thereby, the electrode areas of the movable electrode portions 13 and 33 may be varied. As shown in FIGS. 21 and 22, the first beam structure 10 and the second beam structure 30 are obtained when acceleration is applied by changing the mass or electrode area of the movable electrode portions 13 and 33. The capacity change may be made different.

  Alternatively, as shown in FIGS. 23, 24, and 25, the first capacitor component is formed by forming a silicon nitride film 70 in a portion of the support substrate 2 facing the movable electrode portion 33 of the second beam structure 30. The dielectric constant ε is made different between E1 and the third capacitor component E3. Examples of dielectric materials other than the dioxide film include SiN and SiON. The relative dielectric constant of SiO is “3.9”, but the relative dielectric constant of SiN is “9”. In a broad sense, the first beam structure 10 and the second beam structure 30 are obtained when acceleration is applied by changing the material or thickness of the insulating film between the support substrate 2 and the thin film silicon layer 4. Different capacity changes.

  In addition, as shown in FIG. 26 as an alternative configuration to FIG. 11, the entire outer periphery of the beam structures 10 and 30 in the thin film silicon layer 4 may be used as the signal extraction counter electrode portion 20.

  In addition to the semiconductor acceleration sensor, the present invention may be applied to other mechanical quantities such as a semiconductor yaw rate sensor.

Next, the technical idea that can be grasped from the above-mentioned another example will be described below.
(A) In the semiconductor dynamic quantity sensor according to claim 1,
The movable electrode portion (13) of the first capacitor component (E1) is displaced in a direction perpendicular to the surface of the support substrate (2) by the action of a mechanical quantity while a carrier voltage is applied,
A single chip is formed on the multilayer substrate (1) together with the first and second capacitor components (E1, E2), and a beam structure (30) is defined in the thin film semiconductor layer (4). The movable electrode portion (33) of (30) is arranged to face the support substrate (2) via the gap (34), and the movable electrode portion (33) is applied while a carrier voltage is applied to the movable electrode portion (33). ) Is displaced in the direction orthogonal to the surface of the support substrate (2) by the action of the mechanical quantity, and the capacitance between the movable electrode portion (33) and the support substrate (2) is the first capacitor component. A third capacitor component (E3) that changes in a state different from the capacitance due to the displacement of the movable electrode portion (13) of (E1), and the capacitance difference is taken out from the support substrate (2);
With
The semiconductor dynamic quantity sensor characterized in that the capacitance difference is taken out from the support substrate (2) to the signal take-out counter electrode (20) of the second capacitor constituting part (E2).

With this configuration, a differential capacitance type is obtained, and a structure that can cancel disturbance (noise) and is resistant to noise.
(B) In the semiconductor dynamic quantity sensor described in (a) above, the first beam structure (10) and the second beam structure (30) change the length (L1, L2) of the beam portion. A semiconductor mechanical quantity sensor characterized in that the change in capacitance when the mechanical quantity acts is made different.
(C) In the semiconductor dynamic quantity sensor described in (a) above, the first beam structure (10) and the second beam structure (30) change the width (W1, W2) of the beam portion. A semiconductor mechanical quantity sensor characterized in that the change in capacitance when the mechanical quantity is applied is made different.
(D) In the semiconductor dynamic quantity sensor described in (a) above, the first beam structure (10) and the second beam structure (30) are the mass or electrode of the movable electrode part (13, 33). A semiconductor dynamic quantity sensor characterized in that a change in capacitance when a dynamic quantity is applied is varied by changing an area.
(E) In the semiconductor dynamic quantity sensor according to (a), the first beam structure (10) and the second beam structure (30) include a support substrate (2) and a thin film semiconductor layer (4). A semiconductor dynamic quantity sensor characterized in that a change in capacitance when a dynamic quantity acts is made different by changing a material or a thickness of an insulating film between them.

The top view of the semiconductor acceleration sensor in embodiment. The longitudinal cross-sectional view in the AA line in FIG. The longitudinal cross-sectional view in the BB line in FIG. The conceptual diagram for demonstrating an electrical structure. (A)-(c) is sectional drawing for demonstrating the manufacturing process of a semiconductor acceleration sensor. The circuit block diagram of a capacity | capacitance change detection circuit. Various waveform diagrams. The top view of the semiconductor acceleration sensor of another example. The longitudinal cross-sectional view in the CC line in FIG. The longitudinal cross-sectional view in the DD line in FIG. The top view of the semiconductor acceleration sensor in another example. The longitudinal cross-sectional view in the FF line in FIG. The longitudinal cross-sectional view in the GG line in FIG. The conceptual diagram for demonstrating an electrical structure. The circuit block diagram of a capacity | capacitance change detection circuit. Various waveform diagrams. The longitudinal cross-sectional view of the semiconductor acceleration sensor of another example. The longitudinal cross-sectional view of the semiconductor acceleration sensor of another example. The longitudinal cross-sectional view of the semiconductor acceleration sensor of another example. The top view of the semiconductor acceleration sensor of another example. The top view of the semiconductor acceleration sensor of another example. The top view of the semiconductor acceleration sensor of another example. The top view of the semiconductor acceleration sensor of another example. The longitudinal cross-sectional view in the HH line in FIG. The longitudinal cross-sectional view in the JJ line | wire in FIG. The top view of the semiconductor acceleration sensor of another example. The perspective view of the sensor for demonstrating background art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... SOI substrate, 2 ... Support substrate, 3 ... Insulating film, 4 ... Thin film silicon layer, 10 ... Beam structure, 11a, 11b, 11c, 11d ... Anchor part, 12a, 12b, 12c, 12d ... Beam part, 13 ... movable electrode part, 14 ... gap, 20 ... counter electrode part for signal extraction, 30 ... beam structure, 31a, 31b, 31c, 31d ... anchor part, 32a, 32b, 32c, 32d ... beam part, 33 ... movable electrode 34, a gap, 40, a frame, E1, a first capacitor component, E2, a second capacitor component, E3, a third capacitor component.

Claims (3)

A laminated substrate having an SOI structure in which an insulating film (3) is disposed on one side surface of a support substrate (2) in which a potential made of a semiconductor material is in a floating state, and a thin-film semiconductor layer (4) is disposed on the insulating film (3). (1)
In the thin film semiconductor layer (4), the first beam structure (10) is partitioned and the movable substrate (13) of the first beam structure (10) is a common fixed electrode. ) With the first carrier wave signal generated in synchronization with the clock signal being applied to the movable electrode portion (13) through the air gap (14). A first capacitor in which the capacitance between the movable electrode portion (13) and the support substrate (2) is changed by a displacement in a direction orthogonal to the surface of the support substrate (2), which is a common fixed electrode. A component (E1);
A single chip is formed on the multilayer substrate (1) together with the first capacitor component (E1), and a second beam structure (30) is defined in the thin film semiconductor layer (4). The movable electrode portion (33) of the body (30) is disposed to face the support substrate (2), which is a common fixed electrode, via a gap (34), and the movable electrode portion (33) is synchronized with the clock signal. The surface of the support substrate (2) in which the movable carrier part (33) is a common fixed electrode by the action of a mechanical quantity while the second carrier wave signal having a phase opposite to that of the first carrier wave signal generated is applied. The capacitance between the movable electrode portion (33) and the support substrate (2) displaced in the direction orthogonal to the capacitance is a capacitance due to the displacement of the movable electrode portion (13) of the first beam structure (10). The third capacitor component (E A),
The laminated substrate (1) is integrated into one chip together with the first and third capacitor components (E1, E3), and the signal extraction counter electrode portion (20) is disposed below the thin film semiconductor layer (4). A partition is formed in the presence of the insulating film (3), and the counter electrode portion for signal extraction (20) is disposed opposite to the support substrate (2) which is a fixed electrode of the first and third capacitor components. A second capacitor component (E2),
A switched capacitor circuit (50) electrically connected to the counter electrode portion (20) for signal extraction;
In the switched capacitor circuit (50), the first and second capacitor components (E1) and the third capacitor are displaced by the displacement of the movable electrode portions (13, 33) due to the action of the mechanical quantity when detecting the mechanical quantity. the capacitance difference caused between the components (E3) has been detected,
The switched capacitor circuit (50) includes an operational amplifier (51), a feedback capacitor (52), and a switch element (53).
A signal from the counter electrode portion for signal extraction (20) is input to the inverting input terminal of the operational amplifier (51), and the capacitance of the first capacitor component (E1) is input to the non-inverting input terminal of the operational amplifier. The voltage level appearing in the counter electrode part for signal extraction (20) in a state where C1 and the capacitance C3 of the third capacitor component (E3) are equal is input,
The switch element (53) is turned on for a predetermined time at a timing when the first carrier signal rises and the second carrier signal falls by a trigger signal generated in synchronization with the clock signal,
The operation of the switched capacitor circuit (50) is as follows.
Vcc is applied to the movable electrode part (13) of the first beam structure (10) by the first carrier wave signal, and the movable electrode part (33) of the second beam structure (30) by the second carrier wave signal. ) Is applied with a voltage of 0 volts, the switch element (53) is turned on, and the timing T1 at which the output voltage Vo from the switched capacitor circuit (50) becomes Vcc / 2,
A timing T2 at which a predetermined time elapses from the timing T1 and the switch element (53) is turned off;
After the timing T2, the first carrier signal and the second carrier signal are switched, and the output voltage Vo is changed between the capacitance C1 of the first capacitor component (E1) and the third capacitor component (E3). And a timing T3 that changes in accordance with a differential change amount of the capacitor C3 . The silicon nitride film (70) is formed on a portion of the support substrate (2) facing the movable electrode portion (33) of the second beam structure (30) . Semiconductor dynamic quantity sensor. It has a shield layer to which a constant voltage is applied to surround the first beam structure (10), the second beam structure (30), and the signal extraction counter electrode portion (20). The semiconductor dynamic quantity sensor according to claim 1 or 2.

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