JP5531806B2 - Capacitive inertial force sensor - Google Patents

Description

  The present invention is a capacitive inertial force sensor that includes a movable electrode that is displaced according to an inertial force, and a fixed electrode that is disposed opposite to the movable electrode, and that outputs a detection signal according to a change in capacitance between the movable electrode and the fixed electrode. About.

  Conventionally, as a capacitive inertial force sensor that includes a movable electrode that is displaced according to an inertial force, and a fixed electrode that is disposed opposite to the movable electrode, and that outputs a detection signal according to a capacitance change between the movable electrode and the fixed electrode, For example, as shown in Patent Document 1, there is known one for the purpose of detecting inertial force in a wide range.

  In Patent Document 1, a movable member having a weight action is mounted on a substrate surface in a doubly supported beam form by a support member so that the movable member can be displaced in a direction parallel to the substrate surface. An electrode is provided so as to protrude parallel to the substrate surface. Further, a fixed electrode is provided on the surface of the substrate so as to form a capacitance so as to face the lower surface of each movable electrode when the input acceleration is zero. That is, when the acceleration acts on the movable member and the movable electrode is displaced together with the movable member, the facing area of the movable electrode and the fixed electrode changes, and the change in capacitance accompanying this is detected as an acceleration signal. Yes.

  In the plurality of capacitance detection units including the movable electrode and the fixed electrode, the detection area is expanded by making the opposing areas of the movable electrode and the fixed electrode different when the input acceleration is zero.

JP 2004-286736 A

  However, in Patent Document 1, an electrode size for securing a capacitance change amount is required for each capacitance detection unit (movable electrode and fixed electrode) having different facing areas. Therefore, the sensor size increases in the direction along the lower surface (or upper surface) of the movable electrode.

  Another possible method is to widen the inertial force detection range by changing the gain in the processing circuit. However, in this case, noise is also amplified when a small capacitance change is amplified, and the inertial force detection accuracy deteriorates.

  In view of the above-described problems, the present invention provides a capacitive inertial force sensor that can detect a wide range of inertial forces while suppressing an increase in physique in a direction along the lower surface (or upper surface) of the movable electrode, while suppressing deterioration in detection accuracy. The purpose is to provide.

In order to achieve the above object, the invention described in claim 1
A capacitive inertial force sensor that includes a movable electrode that is displaced in a predetermined direction in accordance with an inertial force, and a fixed electrode that is disposed opposite the movable electrode, and that outputs a detection signal in accordance with a change in capacitance between the movable electrode and the fixed electrode. There,
As a fixed electrode,
A first fixed electrode disposed opposite to a side surface of the movable electrode perpendicular to the displacement direction so that a distance between the movable electrode and the movable electrode changes according to the displacement of the movable electrode;
A second fixed electrode disposed opposite to at least one of the upper surface and the lower surface of the movable electrode facing the first fixed electrode so that the area facing the movable electrode changes with the displacement of the movable electrode ,
The detection signal according to the capacitance change between the movable electrode and the first fixed electrode and the detection signal according to the capacitance change between the movable electrode and the second fixed electrode are for detecting an inertial force acting in the same direction. Of
The detection signal corresponding to the capacitance change between the movable electrode and the first fixed electrode is used as a low inertia force detection signal for detecting a relatively low inertia force, and the detection signal between the movable electrode and the second fixed electrode is used. The detection signal corresponding to the capacitance change is used as a high inertia force detection signal for detecting a relatively high inertia force .

  In the present invention, the capacitance of the capacitor configured between the movable electrode and the first fixed electrode changes as the opposing distance changes, and the capacitance of the capacitor configured between the movable electrode and the second fixed electrode is It changes as the facing area changes. As described above, since there are the capacitor whose facing distance changes and the capacitor whose facing area changes according to the displacement of the movable electrode, a wide range of inertial force can be detected.

  In addition, in a capacitor in which the facing area changes, the electrode size increases in order to ensure the amount of capacitance change. In the present invention, the plurality of second fixed electrodes are not arranged in parallel so as to face each other in the direction along the lower surface (or upper surface) of the movable electrode when the inertial force does not act, but opposed to the movable electrode. The first fixed electrode is provided so that the distance changes. Therefore, an increase in sensor size in the direction along the lower surface of the movable electrode can be suppressed as compared with a configuration having a plurality of capacitors having different facing areas.

  Further, since the gain in the detection circuit (processing circuit) is not changed, it is possible to suppress deterioration in detection accuracy of inertial force due to noise amplification.

  As described above, according to the present invention, the capacitive inertial force sensor capable of detecting a wide range of inertial force can suppress an increase in physique in a direction along the lower surface (or upper surface) of the movable electrode, and can suppress deterioration in detection accuracy. Can be provided.

As claimed in claim 2,
A through-hole extending in the thickness direction of the support substrate is formed in the semiconductor layer disposed on one surface of the support substrate via the insulating layer, and the movable electrode and the first fixed electrode are partitioned,
Between the one surface of the support substrate and the semiconductor layer, the second fixed electrode is disposed at a portion facing the lower surface of the movable electrode on the support substrate side,
It is preferable that the cavity portion connected to the through hole is formed by removing the insulating layer immediately below the movable electrode and the first fixed electrode and immediately above the second fixed electrode.

  Since the capacitive inertial force sensor having the first fixed electrode facing the side surface of the movable electrode and the second fixed electrode facing the lower surface of the movable electrode can be configured with one chip, the sensor configuration is simplified. can do.

  According to a third aspect of the present invention, the insulating layer is disposed on the support substrate side of the first insulating layer adjacent to the semiconductor layer, and serves as a stopper when removing the first insulating layer. It is preferable that the second fixed electrode is formed on the second insulating layer, including the second insulating layer.

  According to this, the area made into the cavity part to remove among the insulating layers can be limited only to the first insulating layer by the second insulating layer.

  According to a fourth aspect of the present invention, the second fixed electrode is preferably made of the same material as that of the lower wiring disposed between the support substrate and the semiconductor layer and disposed in the same layer as the lower wiring.

  The lower wiring is a function of electrically connecting a plurality of regions partitioned into semiconductor layers by through holes, a function of cross wiring, that is, a three-dimensional wiring arrangement, and a function of electrically connecting the semiconductor layer and the semiconductor substrate. Etc. In this invention, since a 2nd fixed electrode can be formed with such a lower wiring, a sensor structure and a manufacturing process can be simplified.

As claimed in claim 5,
A through-hole extending in the thickness direction of the support substrate is formed in the semiconductor layer disposed on one surface of the support substrate via the insulating layer, and the movable electrode and the first fixed electrode are partitioned,
In the opposing region between the support substrate and the semiconductor layer, a cavity portion connected to the through hole is formed by removing the insulating layer immediately below the movable electrode and the first fixed electrode,
A fixing member is fixed to the surface of the semiconductor layer opposite to the insulating layer with a gap between the movable electrode and the first fixed electrode, and the fixed member is second fixed to a portion facing the upper surface of the movable electrode. It is good also as a structure which has an electrode.

  According to this, since it can be comprised by the fixed member provided with the chip | tip provided with the 1st fixed electrode facing the movable electrode and the side surface of this movable electrode at least, and the 2nd fixed electrode facing the upper surface of a movable electrode. The sensor configuration can be simplified.

  Preferably, a cap for sealing the movable electrode and the fixed electrode is preferably used as the fixed member.

  In a capacitive inertial force sensor having a movable electrode that is displaced in accordance with an inertial force, a sealing cap is provided on the surface of the semiconductor layer in order to suppress the biting of foreign matter. By providing the fixed electrode, it is possible to configure a capacitive inertial force sensor including a second fixed electrode facing the upper surface of the movable electrode without increasing the number of parts.

  As described in claim 7, it is preferable that the second fixed electrode has the same shape and size as the movable electrode. According to this, in the positional relationship in which the second fixed electrode is projected onto the movable electrode forming surface, when the movable electrode and the second fixed electrode completely coincide with each other, the opposing area becomes the largest, and the deviation from the completely coincidence state ( The larger the (displacement), the smaller the facing area. Therefore, it is possible to increase the capacitance while suppressing an increase in the sensor size in the direction along the lower surface of the movable electrode.

  In addition, if a comb-tooth shape is employ | adopted as an electrode shape of a movable electrode as described in Claim 8, the opposing area with a 1st fixed electrode can be increased, and this can improve the detection precision of inertial force.

It is a top view showing a schematic structure of a capacity type inertial force sensor concerning a 1st embodiment. It is sectional drawing which follows the II-II line | wire of FIG. It is the figure which modeled the characteristic part of the capacitive inertial force sensor shown in FIG. FIG. 2 is a diagram showing an example of a detection circuit of the capacitive inertial force sensor shown in FIG. It is a top view which shows a modification. It is sectional drawing which shows schematic structure of the capacitive inertial force sensor which concerns on 2nd Embodiment. It is sectional drawing which shows schematic structure of the capacitive inertial force sensor which concerns on 3rd Embodiment. It is the figure which modeled the characteristic part of the capacitive inertial force sensor shown in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
In the following embodiments and modifications, the same reference numerals are given to common or related elements. For convenience, the thickness direction of the substrate (or support substrate) is the vertical direction, and the direction perpendicular to the thickness direction is the horizontal direction.

  In the present embodiment, an example of a capacitive acceleration sensor that detects acceleration as inertial force is shown as a capacitive inertial force sensor. In addition to the capacitive acceleration sensor, a capacitive angular velocity sensor can be employed.

  As shown in FIGS. 1 and 2, the capacitive inertial force sensor 10 according to the present embodiment is configured on a substrate 20 (one chip) in which a semiconductor layer 23 is disposed on a support substrate 21 via an insulating layer 22. ing. Then, as a main part, a movable part 30 configured to be displaceable in a predetermined direction in response to application of inertial force (acceleration), and fixed parts 40 and 60 for detecting inertial force paired with the movable part 30. And have.

  As the substrate 20, a so-called SOI (Silicon On Insulator) substrate or SIMOX (Silicon IMplanted Oxide) substrate can be used. In this embodiment, two insulating layers 24 and 25 are laminated between a support substrate 21 made of single crystal silicon and a semiconductor layer 23 made of single crystal silicon whose impurity concentration is adjusted to a high concentration. A substrate 20 with a layer 22 interposed is employed. In the present embodiment, the first insulating layer 24 disposed on the support substrate 21 and the second insulating layer 25 disposed on the first insulating layer 24 are both made of a silicon oxide film.

  As the semiconductor layer 23, polycrystalline silicon deposited on the insulating layer 22 by a CVD method or the like can be employed instead of single crystal silicon. The insulating layer 22 is not limited to a silicon oxide film, and a silicon nitride film or a multilayer film of a silicon oxide film and a silicon nitride film can be employed.

  The substrate 20 has been subjected to well-known micromachining, and the semiconductor layer 23 and the insulating layer 22 are formed with through holes 26 extending in the vertical direction and penetrating the semiconductor layer 23. The movable portion 30, the first fixed portion 40, and the peripheral portion 50 surrounding the movable portion 30 and the first fixed portion 40 are partitioned into a plurality of regions.

  The movable portion 30 is a beam structure formed by dividing the semiconductor layer 23 by the through-holes 26 and made up of beams (beams) extending in the lateral direction. The movable electrode 31, the weight portion 32, and the spring portion 33. have. Moreover, the width of each beam which comprises each component 31, 32, 33 of the movable part 30 is uniform.

  As shown in FIG. 1, the weight portion 32 serving as a mass on which acceleration acts has an outer periphery (outer frame) having a planar rectangle, and the insulating layer 22 immediately below the weight portion 32 is removed by etching. It has a mesh structure (lattice shape). That is, the weight part 32 has a lattice-like beam structure. The movable electrode 31 is formed in a cantilever shape so as to protrude from one surface of the weight portion 32 along the longitudinal direction so as to be orthogonal to the longitudinal direction of the weight portion 32. In the example shown in FIG. Is provided. Further, spring portions 33 having a rectangular frame-shaped beam structure are respectively connected to both ends of the weight portion 32 on the long side, and each spring portion 33 is movable on the support substrate 21 via the insulating layer 22. It is connected to an anchor 34 as a support portion for supporting 30.

  Immediately below the movable electrode 31, the weight part 32, and the spring part 33 (each beam constituting the spring part 33), the cavity part 27 is formed by removing the insulating layer 22 by selective etching so that the movable part 30 is movable. Is formed. The spring portion 33 connected to the weight portion 32 has a spring function of being displaced in a direction orthogonal to the longitudinal direction. For this reason, when the weight portion 32 receives an acceleration including a component in the longitudinal direction, the weight portion 32 and the movable electrode 31 are displaced along the longitudinal direction of the weight portion 32 and return to the original position due to the disappearance of the acceleration. It has become. In FIG. 1, the displacement direction is indicated by a white arrow.

  The semiconductor layer 23 has a surface 23a opposite to the insulating layer 22 (hereinafter, simply referred to as the surface 23a), and one side of the anchor 34 has a movable electrode pad 35 formed by patterning a metal layer such as aluminum. Is formed.

  Thus, the movable part 30 is a beam structure in which the beam constituting the movable electrode 31, the beam constituting the weight part 32, and the beam constituting the spring part 33 are connected to each other. Both ends of the beam structure are fixed to the anchor 34.

  The first fixed portion 40 includes a first fixed electrode 41, a fixed electrode wiring portion 42, and a fixed electrode pad 43. The fixed electrode wiring portion 42 functions as a wire that electrically connects the first fixed electrode 41 and the fixed electrode pad 43 and also functions as an anchor that supports the first fixed electrode 41. The fixed electrode wiring portion 42 is arranged in parallel with the weight portion 32, and the first fixed electrode 41 extending from the fixed electrode wiring portion 42 is in relation to the side surface 31 a of the movable electrode 31 protruding from the side surface of the weight portion 32. While having a predetermined detection interval (gap), they are arranged to face each other in parallel.

  As described above, the first fixed electrode 41 is disposed so as to face the side surface 31 a perpendicular to the displacement direction of the movable electrode 31 so that the facing distance to the movable electrode 31 changes with the displacement of the movable electrode 31. That is, the capacitance C1 of the capacitor formed between the movable electrode 31 and the first fixed electrode 41 changes due to the change in the facing distance between the movable electrode 31 and the first fixed electrode 41 as the movable electrode 31 is displaced. It is like that.

  The same number of first fixed electrodes 41 as the movable electrodes 31 are provided. In addition, a cavity 27 is formed directly under the first fixed electrode 41 by selective etching of the insulating layer 22 like the movable part 30, so that the first fixed electrode 41 is separated from the fixed electrode wiring part 42. Has been supported. That is, the first fixed electrode 41 also has a beam structure (cantilever beam). And the width of each beam which comprises the 1st fixed electrode 41 is also the same as the width of the beam which comprises each component 31,32,33 of the movable part 30. FIG. In the present embodiment, the first fixed electrode 41 has a hollow structure so that the width of the beam is constant.

  In the fixed electrode wiring portion 42, a fixed electrode pad 43 is formed on the surface 23 a of the semiconductor layer 23.

  Further, as shown in FIG. 1, a pad 51 is also formed on the surface 23 a of the semiconductor layer 23 in the peripheral portion 50, and the peripheral portion 50 in the semiconductor layer 23 is fixed to a predetermined potential via the pad 51. Be able to.

  On the other hand, the second fixed portion 60 includes a second fixed electrode 61 and an island 63 having a fixed electrode pad 62 formed on the surface 23a. The second fixed electrode 61 and the island 63 (fixed electrode pad 62) are electrically connected by the lower wiring 70.

  The second fixed electrode 61 is formed on the surface 21 a of the support substrate 21 at a portion facing the lower surface 31 b of the movable electrode 31 with the first insulating layer 24 interposed therebetween. The same number (two) of the second fixed electrodes 61 as the movable electrodes 31 are provided. In addition, a cavity 27 is formed immediately above the second fixed electrode 61 by selective etching of the insulating layer 22 (second insulating layer 25).

  In the present embodiment, the second fixed electrode 61 is configured by patterning a polycrystalline silicon layer whose concentration is adjusted by implanting impurities so as to have the same shape and size as the movable electrode 31. The second fixed electrode 61 is configured such that the movable electrode 31 and the second fixed electrode 61 completely coincide with each other in a positional relationship projected onto the formation surface (semiconductor layer 23) of the movable electrode 31 in a state where no acceleration is applied. ing. In FIG. 1, for convenience, the second fixed electrode 61 positioned immediately below the movable electrode 31 is also illustrated.

  As described above, the second fixed electrode 61 is disposed so as to face the lower surface 31 b of the movable electrode 31 so that the facing area of the second fixed electrode 61 changes with the displacement of the movable electrode 31. That is, the capacitance C2 of the capacitor formed between the movable electrode 31 and the second fixed electrode 61 changes due to the change in the facing area between the movable electrode 31 and the second fixed electrode 61 as the movable electrode 31 is displaced. It is like that.

  Further, the lower wiring 70 is also disposed on the first insulating layer 24 and, like the second fixed electrode 61, is configured by patterning a polycrystalline silicon layer whose concentration is adjusted by implantation of impurities. The two second fixed electrodes 61 are connected to each other. Reference numeral 71 indicated by a broken line in FIG. 1 is a contact formed on the second insulating layer 25 and connecting the lower wiring 70 and the island 63.

  Next, a manufacturing method of the above-described capacitive inertial force sensor 10 will be described.

  First, a silicon oxide film as the first insulating layer 24 is formed on the surface 21a of the support substrate 21 made of single crystal silicon. Next, a polycrystalline silicon layer doped with impurities at a high concentration is formed on the first insulating layer 24 to a thickness of 0.5 to 2 μm and patterned. Thus, the second fixed electrode 61 and the lower wiring 70 are obtained. Next, a silicon oxide film as the second insulating layer 25 is formed on the first insulating layer 24 so as to cover the second fixed electrode 61 and the lower wiring 70 by CVD or the like. Then, a through hole for the contact 71 is formed at a predetermined position of the second insulating layer 25, and a polycrystalline silicon layer doped with impurities at a high concentration is formed on the second insulating layer 25 so as to fill the through hole. It is formed with a thickness of 5 to 50 μm. Thereby, the semiconductor layer 23 and the contact 71 are obtained.

  Next, after a wiring including pads 35, 43, 51, 62 and the like is formed on the surface 23a of the semiconductor layer 23, the semiconductor layer 23 is anisotropically etched (for example, RIE) using a mask to form the semiconductor layer 23. The through hole 26 described above is formed. Thereby, the semiconductor layer 23 is partitioned into a plurality of regions such as the movable portion 30, the first fixed portion 40, and the peripheral portion 50. Then, the insulating layer 22 is selectively etched through the through hole 26 using the mask. The insulating layer 22 is isotropically etched after the through hole 26 is formed.

  At this time, the insulating layer 22 is etched from a portion close to the through hole 26. Therefore, the etching is finished in a state where the second insulating layer 25 immediately above the second fixed electrode 61 and the lower wiring 70 is removed and the first insulating layer 24 immediately below the second fixed electrode 61 and the lower wiring 70 remains.

  As a result, the first insulating layer 24 and the second insulating layer 25 are both removed from the portion immediately below the through hole 26. In addition, immediately below the movable part 30 including the movable electrode 31 and the first fixed electrode 41, the second insulating layer 25 is removed in the portion where the second fixed electrode 61 and the lower wiring 70 are located, and in other portions. The first insulating layer 24 and the second insulating layer 25 are both removed. That is, the cavity 27 is formed immediately below the movable part 30 including the movable electrode 31 and the first fixed electrode 41, and the first fixed electrode 41 of the movable part 30 including the movable electrode 31 and the first fixed part 40 is It will be in the state released with respect to the support substrate 21. FIG. In addition, the second insulating layer 25 located immediately above the second fixed electrode 61 is removed, and a facing region between the second fixed electrode 61 and the semiconductor layer 23 becomes the cavity 27.

  Although not shown, the capacitive inertial force sensor 10 shown in FIGS. 1 and 2 can be obtained through removal of the mask by plasma etching, dicing, and the like.

  As described above, according to the capacitive inertial force sensor 10 according to the present embodiment, when the movable electrode 31 is displaced in the arrow direction shown in FIG. 3 due to the acceleration, the movable electrode 31 and the first fixed electrode 41 Between the movable electrode 31 and the second fixed electrode 61 changes with a change in the facing area. To do. As described above, since the capacitor having the facing distance that changes with the displacement of the movable electrode 31 and the capacitor having the facing area that changes, the inertial force in a wide range can be detected. In FIG. 3, a state in which the movable electrode 31 is displaced in the right direction of the arrow and approaches the first fixed electrode 41 is indicated by a broken line.

  In the present embodiment, a capacitor configured between the movable electrode 31 and the first fixed electrode 41 whose facing distance is changed is used, for example, for vehicle attitude control and inclination angle determination, several G (about 1 to 5 G). For example, a capacitor configured between the movable electrode 31 and the second fixed electrode 61 whose facing area changes is used for detecting high acceleration of about 20 to 100 G, for example, used for an airbag.

  In the present embodiment, in the lateral direction, the plurality of second fixed electrodes 61 are not arranged side by side so that the opposing areas when the inertial force does not act are different, and the movable electrode is arranged with respect to one movable electrode 31. The first fixed electrode 41 is opposed to the side surface 31 a of the 31, and the second fixed electrode 61 is opposed to the lower surface 31 b of the movable electrode 31. The capacitance of the capacitor configured between the movable electrode 31 and the first fixed electrode 41 changes as the facing distance changes. Therefore, the increase in the sensor size in the lateral direction is suppressed compared to a configuration that requires a plurality of capacitors with different facing areas that require a large electrode size to ensure a capacitance change amount. can do.

  Further, in the present embodiment, since a wide range of inertial force can be detected without changing the gain in the processing circuit, it is possible to suppress deterioration in detection accuracy of the inertial force due to noise amplification.

  An example of the detection circuit of the capacitive inertial force sensor 10 shown in this embodiment is shown in FIG. This detection circuit includes capacitance conversion units 100a and 100b that convert a capacitance into a voltage and output a voltage signal, demodulation units 104a and 104b, and amplification units 105a and 105b.

  The capacitance conversion unit 100a includes a capacitor 101a, a switch 102a, and an operational amplifier 103a, and the capacitance conversion unit 100b includes a capacitor 101b, a switch 102b, and an operational amplifier 103b. Each operational amplifier 103a, 103b receives 1/2 (Vcc / 2) of a carrier wave Vcc described later as a reference voltage.

  In the present embodiment, a modulation signal obtained by AM-modulating a carrier wave with an amplitude Vcc is input to the movable electrode pad 35, and the switches 102a and 102b of the capacitance conversion units 100a and 100b are opened and closed at a predetermined timing. As described above, when acceleration is applied, the movable electrode 31 is displaced in accordance with the acceleration, whereby the capacitances C1 and C2 of the capacitors are changed. On the capacitor side constituted between the movable electrode 31 and the first fixed electrode 41 whose facing distance changes, the voltage conversion unit 100a converts the voltage signal into a voltage signal, and then the demodulation unit 104a demodulates and amplifies the amplification unit 105a. Are amplified and output as a detection signal Vout1. On the capacitor side constituted between the movable electrode 31 and the first fixed electrode 61 whose facing area changes, the voltage conversion unit 100b converts the voltage signal into a voltage signal, and then the demodulation unit 104b demodulates and amplifies the amplification unit 105b. Are amplified and output as a detection signal Vout2. Note that these signals may be output after being combined.

  From the above, according to the capacitive inertial force sensor 10 according to the present embodiment, a wide range of inertial force can be detected, and detection while suppressing an increase in the physique in the lateral direction (the direction along the lower surface 31b of the movable electrode 31). Accuracy degradation can be suppressed and provided.

  In the present embodiment, the capacitive inertial force sensor 10 is configured in one chip using the substrate 20 in which the semiconductor layer 23 is disposed on the support substrate 21 via the insulating layer 22. Therefore, the sensor configuration is simplified while having a capacitor whose opposing area changes and a capacitor whose opposing distance changes.

  In the present embodiment, the second fixed electrode 61 is made of the same material as the lower wiring 70 and is disposed in the same layer as the lower wiring 70. Accordingly, since the second fixed electrode 61 can be formed together with the lower wiring 70, the sensor configuration and the manufacturing process can be simplified.

  In the present embodiment, the second fixed electrode 61 has the same shape and size as the movable electrode 31. For this reason, in the positional relationship in which the second fixed electrode 61 is projected onto the formation surface (lower surface 31b) of the movable electrode 31, when the movable electrode 31 and the second fixed electrode 61 are completely coincident with each other, the facing area becomes the largest, and this perfect coincidence. The larger the deviation (displacement) from this state, the smaller the facing area. Accordingly, it is possible to take a large capacity change while suppressing an increase in the sensor size in the lateral direction.

  In the present embodiment, since the movable electrode 31 has a comb shape in which a plurality of movable electrodes 31 protrude from the side surface of the weight portion 32, the movable electrode 31, the first fixed electrode 41, and the like are used. This increases the opposing area, and thereby improves the detection accuracy of the inertial force.

  In the above-described embodiment, an example in which the lower wiring 70 for electrically connecting the second fixed electrode 61 and the island 63 provided with the fixed electrode pad 62 is shown as the lower wiring. However, the lower wiring means a function of electrically connecting a plurality of regions partitioned by the through hole 26 to the semiconductor layer 23, a cross wiring, that is, a function of three-dimensional wiring arrangement, the semiconductor layer 23 and the support substrate 21 It fulfills the function of electrically connecting and the like. Therefore, a configuration in which a lower wiring other than the lower wiring 70 is provided may be employed. In the example shown in FIG. 5, the anchor 34 for the movable electrode 31 and the island 36 having the movable electrode pad 35 formed on the surface are electrically connected by a lower wiring 72 via a contact 71. Further, the anchor 44 for the first fixed electrode 41 and the island 45 having the fixed electrode pad 43 formed on the surface thereof are electrically connected by the lower wiring 73 through the contact 71. And these lower wirings 72 and 73 are comprised using the same material as the 2nd fixed electrode 61 and the lower wiring 70, and are arrange | positioned at the same layer (on the 1st insulating layer 24).

(Second Embodiment)
As shown in FIG. 6, the capacitive inertial force sensor 10 according to the present embodiment has the semiconductor layer 23 on the support substrate 21 via the insulating layer 22, like the capacitive inertial force sensor 10 shown in the first embodiment. The movable electrode 31, the first fixed electrode 41, and the second fixed electrode 61 are configured on the substrate 20 that is disposed.

  In the present embodiment, a third insulating layer 28 that functions as a stopper when the second insulating layer 25 is removed is disposed between the first insulating layer 24 and the second insulating layer 25 described in the first embodiment. It is characterized by that. The second insulating layer 25 corresponds to the first insulating layer adjacent to the semiconductor layer 23 described in the claims, and the third insulating layer 28 corresponds to the support substrate 21 side described in the claims. This corresponds to the second insulating layer. On the third insulating layer 28, the second fixed electrode 61 and the lower wiring (the lower wiring is not shown) are arranged.

  In addition, a through hole 26 is formed in the semiconductor layer 23, and the movable portion 30, the first fixed portion 40, and the peripheral portion 50 are defined in the semiconductor layer 23 by the through hole 26. In addition, a portion of the second insulating layer 25 immediately below the through hole 26, the movable portion 30, and the first fixed electrode 41 is removed, so that a cavity portion 27 that continues to the through hole 26 is configured.

  Next, a manufacturing method of the above-described capacitive inertial force sensor 10 will be described. First, the substrate 20 is prepared. In this substrate 20, a silicon oxide film as the first insulating layer 24 is formed to a thickness of 0.5 to 2 μm on the surface 21a of the support substrate 21 made of single crystal silicon by thermal oxidation or the like. Next, a silicon nitride film as the third insulating layer 28 is formed on the first insulating layer 24 to a thickness of 0.05 to 0.5 μm by LPCVD, plasma CVD, or the like. Then, a polycrystalline silicon layer whose impurity concentration is adjusted to a high concentration is formed on the third insulating layer 28 with a thickness of 0.5 to 2 μm, and is patterned, so that the second fixed electrode 61 and the lower portion are placed at predetermined positions. Form wiring. Next, a silicon oxide film as the second insulating layer 25 is formed with a thickness of about 2 to 5 μm on the third insulating layer 28 so as to cover the second fixed electrode 61 and the lower wiring by CVD or the like. . Then, a polycrystalline silicon layer whose impurity concentration is adjusted to a high concentration is formed on the second insulating layer 25 with a thickness of 5 to 50 μm. Thereby, the semiconductor layer 23 is obtained. If necessary, the surface of the semiconductor layer 23 may be planarized by CMP or the like.

  The rest is basically the same as the release of the movable portion 30 and the first fixed electrode 41 by conventional sacrificial layer etching. Briefly, after forming a wiring including pads 35, 43, 51, 62 on the surface 23a of the semiconductor layer 23, the semiconductor layer 23 is anisotropically etched (for example, RIE) using a mask. Thereby, a through hole 26 extending in the vertical direction and reaching the second insulating layer 25 is formed in the semiconductor layer 23, and the movable portion 30, the first fixed portion 40, and the peripheral portion are formed in the semiconductor layer 23 by the through hole 26. 50 etc. are sectioned.

  Next, using the mask, the second insulating layer 25 is etched with hydrofluoric acid in a gas phase or liquid phase through the through hole 26, and the second hole located immediately below the through hole 26, the movable portion 30, and the first fixed electrode 41. The insulating layer 25 is removed. At this time, since the second fixed electrode 41, the lower wiring, and the third insulating layer 28 function as stoppers, the through hole 26, the movable portion 30, and the second insulating layer 25 located immediately below the first fixed electrode 41 are removed. Thus, the movable part 30 becomes movable. The capacitive inertial force sensor 10 shown in FIG. 6 can be obtained by removing the mask, dicing, and the like.

  Thus, according to the present embodiment, the area of the insulating layer 22 that is removed by etching, that is, the area that forms the cavity 27 can be limited to the second insulating layer 25 by the third insulating layer 28. it can. Further, since the first insulating layer 24 and the third insulating layer 28 remain almost unetched, the second fixed electrode 61 and the lower wiring can be stably disposed on the support substrate 21.

(Third embodiment)
As shown in FIG. 7, the capacitive inertial force sensor 10 according to the present embodiment has a movable electrode 31 (movable part 30) on the surface 23 a of the semiconductor layer 23 compared to the capacitive inertial force sensor 10 shown in the above embodiment. ) And the first fixed electrode 41 (first fixing portion 40), and a fixing member fixed with a gap between the first fixing electrode 41 and the first fixing electrode 41 (second fixing portion 40). A feature is that an electrode 81 is formed.

  In particular, in the example shown in FIG. 7, as the fixed member 80, a sensing cap including a movable electrode 31 is employed as a sealing cap for being positioned in a hermetically sealed space. Specifically, the fixing member 80 (cap) is made of single crystal silicon, and has a protrusion 82 provided in an annular shape at the edge of the surface facing the surface 23 a of the semiconductor layer 23. The protruding portion 82 is fixed to the surface 23a of the semiconductor layer 23 by direct bonding or low-melting glass bonding, and the movable portion 30 is sealed.

  In the example illustrated in FIG. 7, the fixing member 80 is bonded to the semiconductor layer 23 by performing direct bonding at room temperature (room temperature to about 200 ° C.). In addition, the second fixed electrode 81 is formed in a portion 83 of the fixed member 80 facing the surface 23 a, which is surrounded by the protruding portion 82 and facing the upper surface 31 c of the movable electrode 31. Has been. In the present embodiment, the second fixed electrode 81 is formed via the insulating layer 84. Further, it has the same shape and size as the movable electrode 31, and the projection position of the second fixed electrode 81 coincides with the movable electrode 31 in a state where no acceleration is applied.

  As described above, the sensing unit including the movable electrode 31, the first fixed electrode 41, and the second fixed electrodes 61 and 81 is disposed in a hermetically sealed space. In addition, this airtight space can be made into predetermined | prescribed pressure and atmosphere according to the use of a sensor. For example, a vacuum atmosphere is preferable for the angular velocity sensor, and an atmosphere of 1 to several atmospheres or a nitrogen gas atmosphere is preferable for the acceleration sensor.

  As shown in FIG. 7, each of the electrodes 31, 41, 61 has a corresponding lower wiring 70, 72, 73 (only the lower wiring 73 is shown in FIG. 7), and the sensing unit including the movable unit 30 is It is electrically connected to pads 35, 43, 62 located outside the hermetically sealed space. Further, reference numeral 85 shown in FIG. 7 is a through electrode formed in the fixing member 80 that penetrates the opposing surface 83 and the back surface of the opposing surface 83, and reference numeral 86 is a pad connected to the through electrode 85. The through electrode 85 is disposed in the through hole via an insulating film.

  As described above, according to the capacitive inertial force sensor 10 according to the present embodiment, when the movable electrode 31 is displaced in the arrow direction shown in FIG. 8 due to the acceleration, the gap between the movable electrode 31 and the first fixed electrode 41 is obtained. The capacitance C1 of the configured capacitor changes with the change in the facing distance. On the other hand, the capacitance C2 of the capacitor formed between the movable electrode 31 and the second fixed electrodes 61 and 81 changes as the facing area changes. As described above, since the capacitor having the facing distance that changes with the displacement of the movable electrode 31 and the capacitor having the facing area that changes, the inertial force in a wide range can be detected.

  In the present embodiment, there are two second fixed electrodes 61 and 81 whose facing areas change with the displacement of the movable electrode 31. And the capacity | capacitance of the capacitor | condenser respectively comprised by the movable electrode 31 and the 2nd fixed electrode 61 and the movable electrode 31 and the 2nd fixed electrode 81 is synthesize | combined. Therefore, the amount of change in the capacitance of the capacitor configured between the movable electrode 31 and the second fixed electrodes 61 and 81 is increased while suppressing the lateral sensor size and increasing the area of the second fixed electrode facing the movable electrode 31. Can be made larger than a configuration having only one second fixed electrode (for example, the second fixed electrode 61). Further, if the amount of change in capacity is the same, the physique can be reduced in size.

  In the present embodiment, a chip including the movable electrode 31, a first fixed electrode 41 facing the side surface 31a of the movable electrode 31, and a second fixed electrode 61 facing the lower surface 31b of the movable electrode 31, and the movable electrode It is comprised by the fixing member 80 provided with the 2nd fixed electrode 81 facing the upper surface 31c of 31. As shown in FIG. Therefore, the sensor configuration can be simplified.

  In particular, in this embodiment, a cap is employed as the fixing member 80. Therefore, it can be set as the structure provided with the 2nd fixed electrode 81 which opposes the upper surface 31c of the movable electrode 31, suppressing the foreign material biting etc. of the movable electrode 31, and without increasing a number of parts.

  In the present embodiment, the example in which the second fixed electrodes 61 and 81 are provided together with the first fixed electrode 41 as the fixed electrode is shown, but the first fixed electrode 41 and the second fixed electrode 81 are provided (second fixed electrode). The electrode 61 may be omitted).

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  The configurations of the movable unit 30 and the first fixed unit 40 configured in the semiconductor layer 23 are not limited to the examples shown in the above embodiment. For example, the number of movable electrodes 31 is not limited to two. The movable electrode 31 may be provided so as to protrude from both side surfaces of the weight portion 32.

  In the above embodiment, an example of the support substrate 21 made of single crystal silicon has been shown, but the constituent material of the support substrate 21 is not limited to the above example. For example, when made of an insulating material, the second fixed electrode 61 and the lower wiring can be formed on the surface 21 a of the support substrate 21. In this case, when an insulating material that can selectively etch the second insulating layer 25 is selected as the constituent material of the support substrate 21, the insulating layer 22 can include only the second insulating layer 25.

DESCRIPTION OF SYMBOLS 10 ... Capacitive inertial force sensor 22 ... Insulating layer 23 ... Semiconductor layer 25 ... 2nd insulating layer 26 ... Through-hole 27 ... Cavity 28 ... 3rd insulating layer 31 ... Moveable electrode 41 ... First fixed electrode 61 ... Second fixed electrode 80 ... Fixing member (cap)
81 ... Second fixed electrode

Claims (8)

A capacitive inertial force that includes a movable electrode that is displaced in a predetermined direction according to an inertial force, and a fixed electrode that is disposed opposite to the movable electrode, and that outputs a detection signal according to a change in capacitance between the movable electrode and the fixed electrode. A sensor,
As the fixed electrode,
A first fixed electrode disposed opposite to a side surface of the movable electrode that is perpendicular to the displacement direction so that a distance to the movable electrode changes as the movable electrode is displaced;
A second fixed electrode disposed opposite to at least one of an upper surface and a lower surface of the movable electrode facing the first fixed electrode so that an area facing the movable electrode changes with displacement of the movable electrode. ,
The detection signal according to the capacitance change between the movable electrode and the first fixed electrode and the detection signal according to the capacitance change between the movable electrode and the second fixed electrode detect the inertial force acting in the same direction. To do,
A detection signal corresponding to a change in capacitance between the movable electrode and the first fixed electrode is used as a low inertia force detection signal for detecting a relatively low inertia force, and the movable electrode and the second fixed electrode are used. A capacitive inertial force sensor characterized in that a detection signal corresponding to a change in capacitance is used as a high inertial force detection signal for detecting a relatively high inertial force . A through-hole extending in the thickness direction of the support substrate is formed in a semiconductor layer disposed on one surface of the support substrate via an insulating layer, and the movable electrode and the first fixed electrode are partitioned,
Between the one surface of the support substrate and the semiconductor layer, the second fixed electrode is disposed at a portion facing the lower surface of the movable electrode,
2. The cavity portion connected to the through hole is formed by removing the insulating layer immediately below the movable electrode and the first fixed electrode and immediately above the second fixed electrode. Capacitive inertial force sensor. The insulating layer includes a first insulating layer adjacent to the semiconductor layer, and a second insulating layer that is disposed closer to the support substrate than the first insulating layer and serves as a stopper when the first insulating layer is removed. Including
The capacitive inertial force sensor according to claim 2, wherein the second fixed electrode is formed on the second insulating layer.   The second fixed electrode is made of the same material as the lower wiring disposed between the support substrate and the semiconductor layer, and is disposed in the same layer as the lower wiring. The capacitive inertial force sensor according to claim 3. A through-hole extending in the thickness direction of the support substrate is formed in a semiconductor layer disposed on one surface of the support substrate via an insulating layer, and the movable electrode and the first fixed electrode are partitioned,
In the opposing region between the support substrate and the semiconductor layer, a cavity portion that is continuous with the through hole is formed by removing the insulating layer immediately below the movable electrode and the first fixed electrode,
A fixing member is fixed on the surface of the semiconductor layer opposite to the insulating layer, with a gap between the movable electrode and the first fixed electrode,
5. The capacitive inertial force sensor according to claim 1, wherein the fixed member has the second fixed electrode at a portion facing the upper surface of the movable electrode.   The capacitive inertial force sensor according to claim 5, wherein the fixed member is a cap for sealing the movable electrode and the fixed electrode.   The capacitive inertial force sensor according to claim 1, wherein the second fixed electrode has the same shape and size as the movable electrode.   The capacitive inertial force sensor according to claim 1, wherein the movable electrode has a comb shape.

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