WO2010104064A1

WO2010104064A1 - Mems sensor

Info

Publication number: WO2010104064A1
Application number: PCT/JP2010/053864
Authority: WO
Inventors: 亨宮武; 佐藤　清; 菊入　勝也; 小林　潔; 尚信大川
Original assignee: アルプス電気株式会社
Priority date: 2009-03-13
Filing date: 2010-03-09
Publication date: 2010-09-16
Also published as: JPWO2010104064A1

Abstract

Provided is an MEMS sensor having a stable and high detection accuracy specifically with a correct relationship with the thickness of a substrate. The MEMS sensor has: a supporting substrate (first substrate) (1); a function layer (2) having a sensor section (4) and anchor sections (5, 10) which are integrally formed with the sensor section (4); a first bonding layer (3) formed of an insulating material which bonds together the anchor sections (5, 10) and the supporting substrate (1). The sensor section (4) is disposed on the supporting substrate (1) with a space therebetween. The thickness (H1) of the supporting substrate (1) is formed within the range of 10-30 times the thickness (H2) of the function layer (2).

Description

MEMS sensor

The present invention relates to a MEMS sensor formed by bonding an insulating layer between a support substrate and a functional layer having a sensor portion and an anchor portion.

Patent Document 1 below discloses a capacitive dynamic quantity sensor device having a support substrate, a semiconductor layer (functional layer), and a circuit chip.

This patent document defines the relationship between the gap distance between the movable electrode and the support substrate constituting the semiconductor layer, the gap distance between the movable electrode and the circuit chip, and the thickness of the movable electrode.

According to Patent Document 1, the relationship between the gap distance and the thickness of the movable electrode is defined to prevent the movable electrode from running on the fixed electrode.

JP, 2006-084327, A

However, in the invention described in Patent Document 1, the relationship between the thickness of the support substrate and the semiconductor layer (functional layer) and the thickness relationship between the support substrate and the circuit chip are not specified. It was found by experiments described later that these thickness relationships affect the amount of warpage, the stress acting on the anchor portion, and the amount of deformation of the anchor portion in the plane direction. When the amount of warpage of the MEMS sensor is increased or the amount of deformation of the anchor portion in the planar direction is increased, there is a problem that the detection accuracy is lowered.

Therefore, the present invention is intended to solve the above-described conventional problems, and in particular, it is an object of the present invention to provide a MEMS sensor in which stable and highly accurate detection accuracy can be obtained by optimizing the relationship between substrate thicknesses. And

The MEMS sensor according to the present invention is formed of a first substrate, a sensor layer, and a functional layer having an anchor portion integrally formed with the sensor portion, and an insulating material for bonding the anchor portion and the first substrate. A first bonding layer, and the sensor unit is spaced apart from the first substrate,
The thickness of the first substrate may be in the range of 10 times to 30 times the thickness of the functional layer.

As a result, the warp amount of the MEMS sensor can be reduced, and stable and highly accurate detection characteristics can be obtained.

In the present invention, the semiconductor device further includes a second substrate opposed to the first substrate via the functional layer,
The sensor unit may be spaced apart from the first substrate and the second substrate, and the anchor unit may be fixed and supported via the second substrate and the second bonding layer.

In the above invention, the upper and lower portions of the anchor portion are fixed and supported by the bonding layer. Although thermal stress, processing stress, and force based on actual use are applied to the MEMS sensor, as described above, the thickness of the first substrate is 10 times to 30 times the thickness of the functional layer. By forming in the range of, the stress which acts on an anchor part can be reduced effectively. This makes it possible to realize a MEMS sensor having high impact resistance and excellent detection characteristics.

In the above configuration, preferably, the first substrate and the second substrate are formed of the same material. Thereby, the amount of deformation in the planar direction of the anchor portion due to the thermal stress can be reduced.

In the above, it is more preferable that the first substrate and the second substrate be formed to have the same thickness.

Further, in the present invention, it is preferable that the first substrate and the second substrate be formed of silicon.

Alternatively, in the present invention, one of the first substrate and the second substrate may be formed of silicon and the other may be formed of glass, and the first substrate and the second substrate may be formed to have the same thickness. Thereby, the amount of deformation in the planar direction of the anchor portion due to the thermal stress can be reduced.

In the present invention, an insulating layer is provided on the surface of the second substrate facing the first substrate, the second bonding layer is formed of a metal bonding layer, and the second bonding layer is connected to the second bonding layer. The lead layer can be embedded in the insulating layer.

Alternatively, in the present invention, an insulating layer is provided on the surface opposite to the surface facing the first substrate of the second substrate, and the second bonding layer is formed of a metal bonding layer, and the second bonding is performed. A lead layer connected via the layer and the second substrate may be embedded in the insulating layer.

In the present invention, it is preferable that both the first substrate and the functional layer be formed of silicon.

According to the MEMS sensor of the present invention, by optimizing the relationship of the substrate thickness, it is possible to obtain stable and highly accurate detection accuracy as compared with the prior art.

1 (a) is a plan view of the MEMS sensor (acceleration sensor) in the first embodiment, and FIG. 1 (b) is a longitudinal sectional view of the MEMS sensor cut from line AA of FIG. 1 (a) and viewed from the arrow direction. Front view. Fig.2 (a) is a top view of the MEMS sensor (acceleration sensor) in 2nd Embodiment, FIG.2 (b) is a longitudinal cross-section of the MEMS sensor cut | disconnected from the BB line of Fig.2 (a) and seen from the arrow direction. Front view. The partially expanded longitudinal cross-sectional view which expands and shows a part of FIG.2 (b). FIG. 4 is a partially enlarged vertical cross-sectional view of a MEMS sensor showing a cross-sectional shape different from FIG. 3. The schematic diagram for demonstrating curvature amount (lambda) of a MEMS sensor. The graph which shows the relationship of the thickness ratio with respect to the functional layer of a support substrate, and curvature amount. The schematic diagram of the laminated substrate (1/2 model) used by experiment. FIG. 8 is a plan view of the functional layer of FIG. 7; The enlarged schematic diagram of the lamination substrate for explaining an experiment position. The graph which shows the relation between the position of an anchor part, and the maximum stress which acts on an anchor part. The graph which shows the relationship between the thickness ratio to a functional layer of a support substrate, and the maximum stress which acts on an anchor part. The schematic diagram of the laminated substrate used by experiment. The schematic diagram which expanded and showed a part of FIG. 12 for demonstrating the height position of an anchor part, and the position to a X direction. The graph which shows the relationship between the position to the X direction of an anchor part, and a height position (we experimented respectively using the material and thickness of a cap board | substrate which differ). The graph which shows the relationship between the thickness of a cap board | substrate (silicon or glass), and the deformation amount of an anchor part. The graph which shows the relation between the thickness of a cap board (glass), and the position to the direction of X of an anchor part. The graph which shows the relation between the thickness of a cap board (silicon), and the position to the direction of X of an anchor part.

1 (a) is a plan view of the MEMS sensor (acceleration sensor) in the first embodiment, and FIG. 1 (b) is a longitudinal sectional view of the MEMS sensor cut from line AA of FIG. 1 (a) and viewed from the arrow direction. It is a face view.

The MEMS sensor shown in FIG. 1 is formed in a laminated structure having a support substrate (first substrate) 1, a functional layer 2, and a first bonding layer 3. The MEMS sensor is formed, for example, by micromachining an SOI substrate. The support substrate 1 and the functional layer 2 are preferably formed of silicon, and the first bonding layer 3 is preferably formed of silicon oxide. The thickness of the first bonding layer 3 is preferably in the range of 0.5 to 2.0 μm. The width dimension and the length dimension (longitudinal dimension in the XY plane) of the support substrate 1 and the functional layer 2 are about 0.5 to 2.5 mm.

As shown in FIG. 1A, in the functional layer 2, the sensor portion 4,

anchor portions

5 and 10, support beams 6 and the like are formed by fine processing. Furthermore, the sensor unit 4 is configured to have a weight 7, a movable electrode 8 and a fixed electrode 9. As shown in FIG. 1A, the comb-like movable electrode 8 and the comb-like fixed electrode 9 are alternately arranged. The movable electrode 8, the weight 7, the support beam 6 and the anchor 5 are integrally formed. On the other hand, the fixed electrode 9 is formed integrally with the anchor portion 10 in a state of being separated from the movable electrode 8 and the weight portion 7.

As shown in FIG. 1, the

anchor portions

5 and 10 are fixedly supported on the support substrate 1 via the first bonding layer 3. A space is formed between the sensor unit 4 and the support substrate 1.

In the embodiment of FIG. 1, the weight portion 7 is displaced by receiving a force (inertial force) accompanying the acceleration, and based on a change in capacitance between the movable electrode 8 and the fixed electrode 9, the change in acceleration or the magnitude of the acceleration Can be detected.

As shown in FIG. 1 (b), the thickness of the support substrate 1 is H1, and the thickness of the functional layer 2 is H2. In this embodiment, the thickness H2 of the functional layer 2 is constant, but in the embodiment in which the thickness is different depending on the location of the functional layer 2, the thickness H2 of the functional layer 2 is the thickness of the

anchor portions

5 and 10. It is defined. The same applies to the embodiment shown in FIG.

In the present embodiment, the thickness H1 of the support substrate 1 is formed in a range of 10 times to 30 times the thickness H2 of the functional layer 2. The thickness H1 of the support substrate 1 is preferably in the range of 200 to 900 μm, and the thickness H2 of the functional layer 2 is preferably in the range of 20 to 30 μm. As an example, the thickness H2 of the functional layer 2 is about 20 μm, and the thickness H1 of the support substrate 1 is adjusted in the range of 200 μm to 600 μm.

According to experiments described later, it is known that the warpage amount of the MEMS sensor can be effectively reduced by defining the thickness ratio between the support substrate 1 and the functional layer 2 as described above.

Further, as described above, although it has been described that the support substrate 1 and the functional layer 2 are preferably formed of silicon, the present invention is not limited to silicon as long as the support substrate 1 and the functional layer 2 are the same material. The term "same material" as used herein means that mechanical properties (here, Poisson's ratio, Young's modulus, and thermal expansion coefficient) are substantially equal. If each mechanical property is a difference within 10% between the support substrate 1 and the functional layer 2 (a ratio obtained by dividing the difference of the mechanical property by the mechanical property of the larger value), "the same material" Define as Therefore, different materials can be used for the support substrate 1 and the functional layer 2 as long as the mechanical properties are substantially the same.

Fig.2 (a) is a top view of the MEMS sensor (acceleration sensor) in 2nd Embodiment, FIG.2 (b) is a longitudinal cross section of the MEMS sensor cut | disconnected from the BB line of Fig.2 (a), and was seen from the arrow direction. It is a face view. The plan view of FIG. 2A is shown through the support substrate 1.

The MEMS sensor illustrated in FIG. 2 has, for example, a rectangular shape in which the X direction is a long side and the Y direction is a short side.

The MEMS sensor shown in FIG. 2B includes a sensor unit 20 including the support substrate 1, the first bonding layer 3 and the functional layer 2, and the sensor unit facing the sensor unit 20 and formed in the sensor unit 20. A cap member 12 for sealing is stacked. The width dimension and the length dimension (longitudinal dimension in the XY plane) of the sensor unit 20 and the cap member 12 are about 0.5 to 2.5 mm.

The cap member 12 is configured of a cap substrate (second substrate) 13, an insulating layer 14 formed on the surface thereof, and a second bonding layer 15. The insulating layer 14 is preferably formed of silicon oxide. The insulating layer 14 is preferably formed to a thickness of about 0.5 to 2.0 μm. The second bonding layer 15 is preferably formed to a thickness of about 0.5 to 1.5 μm. The material of the second bonding layer 15 will be described later.

FIG. 3 is a partially enlarged longitudinal sectional view showing a part of FIG. 2 (b) in an enlarged manner. However, in FIG. 3, unlike the case of FIG. 2B, the cap member 12 is formed so as to protrude from the sensor unit 20.

As shown in FIG. 3, a conductor pattern is embedded in the insulating layer 14 to form a lead layer 35. The lead layer 35 is separately conducted to the movable electrode and the fixed electrode of the detection portion formed on the functional layer 2 and is conducted to the external connection pads 50 provided outside the MEMS sensor.

As shown in FIG. 2A, a frame layer 11 is formed in the peripheral region of the functional layer 2, and the inside of the frame layer 11 is a forming area of the sensor portion. In FIG. 2A, the frame layer 11 is indicated by oblique lines.

As shown in FIG. 2A, in the functional layer 2, a first hole 26, a second hole 27, and a third hole 28 for defining the outer shape of the sensor portion are formed inside the frame layer 11. The

respective holes

26, 27, 28 pass through the frame layer 11 in the thickness direction.
A frame-shaped first bonding layer 3 is formed in the facing portion of the support substrate 1 and the frame layer 11.

As shown in FIGS. 2A and 2B, the second bonding layer 15 seals the periphery of the sensor portion between the frame layer 11 and the insulating layer 14 formed on the facing surface of the cap member 12. doing.

As shown in FIG. 2A, the insides of the

respective holes

26, 27, 28 are

sensor portions

16, 17, 18.

The MEMS sensor shown in FIG. 2 can detect the acceleration in the Z direction of the direction orthogonal to the substrate surface of the support substrate 1 by the operation of the first movable body 41 provided in the first sensor unit 16. Further, by the operation of the second movable body 21 provided in the second sensor unit 17, acceleration in the Y direction parallel to the substrate surface of the support substrate 1 can be detected, and the third sensor unit 18 is provided with a third acceleration. The acceleration of the X direction orthogonal to the Z direction and the Y direction can be detected by the operation of the movable body 21A.

For example, in the second sensor unit 17, the second movable body 21 is provided inside the second hole 27. The second movable body 21 is supported movably mainly in the Y direction by the

anchor portions

23 and 25.

As shown in FIG. 2 (b), the

anchor portions

23 and 25 are joined via the insulating and insulating layer 14 and the second bonding layer 15.

As shown in FIG. 2 (b), the

anchor portions

23 and 25 are fixed by being sandwiched from above and below by the first bonding layer 3 and the second bonding layer 15, but the second movable body 21 is And is not bonded to the support substrate 1 nor to the insulating layer 14.

The second movable body 21 shown in FIG. 2A is provided with a plurality of movable electrodes in a comb shape.
At least one of the

anchor portions

23 and 25 is electrically connected to the lead layer 35 provided inside the insulating layer 14 via the second bonding layer 15, and the lead layer 35 is a cap member protruding to the outside of the sensor unit 20. It is conductively connected to an external connection pad 50 provided on the exposed surface of 12 (see FIG. 3).

In the second sensor unit 17 shown in FIG. 2A, the fixing

portions

31 and 32 are provided. The anchor portion 33 is integrally formed on the fixing portion 31. Further, the anchor portion 34 is integrally formed with the fixing portion 32.

The anchor portion 33 is bonded to the support substrate 1 via the first bonding layer 3. Further, the insulating layer 14 formed on the surface of the cap substrate 13 and the anchor portion 33 are bonded by the second bonding layer 15.

As shown in FIG. 2A, in the fixing portion 31, a plurality of fixed electrodes are integrally formed in a comb shape. Each fixed electrode is inserted between a plurality of movable electrodes integrally formed on the second movable body 21. The fixing portion 32 also has the same configuration as the fixing portion 31.

The

anchor portions

33 and 34 are connected to the second bonding layer 15, and the second bonding layer 15 is connected to a lead layer provided inside the insulating layer 14. The lead layer is conductively connected to an external connection pad 50 provided on the exposed surface of the cap member 12 protruding to the outside of the sensor unit 20.

The second sensor unit 17 of the MEMS sensor shown in FIG. 2 responds to the acceleration in the Y1 direction or the Y2 direction. For example, when acceleration in the Y1 direction acts on the MEMS sensor, the reaction causes the second movable body 21 to move in the Y2 direction. At this time, the capacitance changes as the facing distance between the movable electrode and the fixed electrode changes. Then, it is possible to detect the change in acceleration acting in the Y1 direction and the magnitude of the acceleration by the change in capacitance.

The structure of the third sensor unit 18 shown in FIG. 2A is exactly the same as that obtained by rotating the structure of the second sensor unit 17 by 90 degrees. The third sensor unit 18 operates in reaction to the acceleration in the X1-X2 direction. When acceleration in the X1 or X2 direction acts on the MEMS sensor, the inertial force moves the third movable body 21A in the direction opposite to the acting direction of the acceleration, and the amount of movement at that time is the movable electrode and the fixed electrode It is detected as a change in capacitance at the opposing detection unit.

Next, in the first sensor unit 16, a first movable body 41 is provided. The first movable body 41 is supported by the

anchor portions

42 and 42 so as to be movable in the Z direction. Each

anchor portion

42, 42 is bonded to the support substrate 1 by the first bonding layer 3. The

anchor portions

42 and 42 are bonded to the insulating layer 14 formed on the surface of the cap substrate 13 by the second bonding layer 15. The first movable body 41 is separated from the support substrate 1 and the insulating layer 14 so that movement in the Z direction is possible.

As shown in FIG. 2A, on the first movable body 41, a plurality of movable electrodes are integrally formed in a comb shape. Then, at least one of the

anchor portions

42 and 42 is electrically connected to the lead layer in the insulating layer 14 via the second bonding layer 15, and the lead layer is an exposed surface of the cap member 12 protruding outside the sensor unit 20. It electrically connects to the external connection pad 50 provided in.

As shown in FIG. 2, fixed

portions

51 and 53 are formed separately from the first movable body 41 inside the first movable body 41. The anchor portion 52 is integrally formed with the fixing portion 51, and the anchor portion 54 is integrally formed with the fixing portion 53.

As shown in FIG. 2 (b), the anchor portion 52 and the anchor portion 54 are respectively bonded to the support substrate 1 by the first bonding layer 3. The anchor portion 52 and the anchor portion 54 are respectively bonded to the insulating layer 14 formed on the surface of the cap substrate 13 by the second bonding layer 15. However, in the fixing

portions

51 and 53, portions other than the

anchor portions

52 and 54 are separated from the support substrate 1 and the insulating layer 14.

In the fixing

portions

51 and 53, a plurality of fixed electrodes are integrally formed in a comb shape. The fixed electrode is bonded to the lead layer in the insulating layer 14 via the

anchor portions

52 and 54 and the second bonding layer 15. The lead layer is conductively connected to an external connection pad 50 provided on the exposed surface of the cap member 12 protruding outside the sensor unit 20.

The first sensor unit 16 can respond to acceleration in the Z direction. For example, when an acceleration in the Z2 direction acts on the MENS sensor, the reaction causes the first movable body 41 to move in the Z1 direction. At this time, the capacitance changes due to the change in the facing area between the movable electrode and the fixed electrode, and the magnitude and change in acceleration can be detected based on the change in capacitance.

As shown in FIG. 3, the second bonding layer 15 is formed by eutectic bonding of a first metal layer 56 provided on the sensor unit 20 side and a second metal layer 57 provided on the cap member 12 side. It is formed by diffusion bonding. Examples of the combination of materials of the first metal layer 56 and the second metal layer 57 include aluminum-germanium, aluminum-zinc, gold-silicon, gold-indium, gold-germanium, gold-tin and the like. The combination of these metals makes it possible to perform bonding at a relatively low temperature of 450 ° C. or less, which is a temperature below the melting point of each metal.

The MEMS sensor shown in FIG. 2 constitutes a three-axis acceleration sensor. In this embodiment, the upper and lower portions of each of the

anchor portions

23, 25, 33, 34, 42, 52, 54 are fixedly supported on the side of the support substrate 1 and the cap substrate 13 by the bonding layers 3 and 15. As in the embodiment of FIG. 1, the thickness H1 of the support substrate 1 is formed in a range of 10 times to 30 times the thickness H2 of the functional layer 2.

A thermal stress, a processing stress, and a force based on the actual use are applied to the MEMS sensor, but the thickness H1 of the support substrate (first substrate) 1 is set to the thickness H2 of the functional layer 2 as described above. On the other hand, by forming in the range of 10 times to 30 times, the stress acting on each

anchor portion

23, 25, 33, 34, 42, 52, 54 can be effectively reduced. This makes it possible to realize a MEMS sensor having high impact resistance and excellent detection characteristics.

By the way, in the MEMS sensor shown in FIG. 2, a cap substrate 13 is provided in addition to the support substrate 1 and the functional layer 2. The thickness of the cap substrate 13 is H3.

It is preferable that the support substrate 1 and the cap substrate 13 be formed of the same material. As described above, "the same material" indicates that mechanical properties (here, Poisson's ratio, Young's modulus, and thermal expansion coefficient) are substantially equal. At this time, it is preferable that the support substrate 1 and the cap substrate 13 be formed of silicon.

When the support substrate 1 and the cap substrate 13 are formed of the same material, the thickness H3 of the cap substrate 13 can be defined within the range of the thickness H1 of the support substrate 1 described above. It is preferable to make H1 and the thickness H3 of the cap substrate 13 the same. The manufacturing error is in the range of the same thickness.

Alternatively, one of the support substrate 1 and the cap substrate 13 may be made of silicon and the other may be made of glass, and the thickness H1 of the support substrate 1 and the thickness H3 of the cap substrate 13 may be the same. Preferably, the support substrate 1 is formed of silicon and the cap substrate 13 is formed of glass.

Even in the configuration in which the cap substrate 13 is provided as described above, the planar direction of each

anchor portion

23, 25, 33, 34, 42, 52, 54 resulting from the thermal stress can be obtained by matching the material and thickness with the support substrate 1. The amount of deformation in the (XY plane direction) can be reduced. Therefore, it is possible to obtain more stable, highly accurate detection characteristics more effectively.

In the embodiment shown in FIGS. 2 and 3, the cap substrate 13 may be an IC substrate.
Also, it is possible to make the cross-sectional structure shown in FIG. 4 differently from FIG.

In the embodiment shown in FIG. 4, a through wiring layer 30 penetrating the cap substrate 13 is provided. The through wiring layer 30 can be formed separately from the cap substrate 13. An insulating layer 29 insulates between the through wiring layer 30 and the cap substrate 13. As shown in FIG. 4, the through wiring layer 30 and the anchor portion are joined via the second bonding layer 15 composed of the first metal layer 56 and the second metal layer 57 described in FIG. There is. In addition, the insulating layer 29 covers the surface opposite to the surface facing the functional layer 2 of the cap substrate 13 and the opposite surface 13 a side, and as shown in FIG. 4, the lead layer 37 in contact with the through wiring layer 30 is inside the insulating layer 29. It is formed. A part of the lead layer 37 is exposed from the surface of the insulating layer 29 to constitute an external connection pad.

The present embodiment is not limited to the acceleration sensor. In the above embodiment, the MEMS sensor 1 of the capacitance type is used, but the invention is not limited to the capacitance type.

(The thickness ratio of the support substrate (first substrate) to the functional layer-Experiment of the amount of warpage)
A simulation experiment was conducted using a laminated substrate in which a functional layer made of silicon is stacked on a supporting substrate made of silicon in a circular shape having a diameter of 152 mm. The Poisson's ratio of the support substrate was 0.17. Young's modulus was 150 GPa.

The thickness H2 of the functional layer was unified at 20 μm. In addition, since a first bonding layer made of an insulating material is actually present between the support substrate and the functional layer, the experiment was performed with a film stress of 10 MPa due to the presence of the first bonding layer. The film stress of 10 MPa corresponds to the case where the first bonding layer is made of silicon oxide of about 1 to 2 μm.

The warpage amount λ of the MEMS sensor can be determined by λ = 3σ (1−ν) (H2) ² L ² / (4E (H 1) ² ). Where σ is the film stress, ν is the Poisson's ratio of the support substrate, H 2 is the thickness of the functional layer, L is the length (diameter) of the support substrate, E is the Young's modulus of the support substrate, and H 1 is the thickness of the support substrate is there.

In the experiment, when the thickness H1 of the support substrate was changed at intervals of 50 μm from 100 μm to 650 μm, the warpage amount λ shown in FIG. 5 was determined. The experimental results are shown in FIG.

As shown in FIG. 6, it was found that when the thickness H1 of the support substrate is set in a range of 10 times to 30 times the thickness H2 of the functional layer, the amount of warpage can be appropriately reduced. Here, as shown in FIG. 6, the larger the thickness ratio of the support substrate to the functional layer, the smaller the amount of warpage. However, if the thickness ratio is too large, the height of the MEMS sensor is reduced ( The upper limit is set to 30 times because the size reduction is inhibited. In addition, it was set as more preferable to set the thickness H1 of the support substrate in the range of 20 times to 30 times the thickness H2 of the functional layer.

(Thickness ratio of support substrate (first substrate) to functional layer-Experiment of stress on anchor portion)
A simulation experiment was conducted using a laminated substrate in which a support substrate (first substrate) made of silicon, a functional layer made of silicon, and a cap substrate (second substrate) made of silicon shown in FIG. 7 are stacked.

The Young's modulus of silicon was 150 GPa, and the Poisson's ratio was 0.17. FIG. 8 is a plan view of the functional layer shown in FIG. The laminated substrate according to this experiment is a half model of the MEMS sensor of FIG. As shown in FIG. 8, the functional layer is composed of an anchor portion and a frame layer fixed and supported on both the support substrate side and the cap substrate side.

In the experiment, the thickness H3 of the cap substrate was fixed at 200 μm and the thickness H2 of the functional layer was fixed at 20 μm. Further, the width dimension of the supporting substrate and the cap substrate is 2.5 mm, and the length dimension orthogonal to the width dimension is 0.76 mm.

By the way, a thermal stress, a processing stress, and a force of up to about 2 N are applied to the MEMS sensor at the time of actual use. Therefore, both sides of the laminated substrate are fixed, and the force of 1 N (upward toward the cap substrate) from the center position of the lower surface of the support substrate shown in FIG. The stress acting on the anchor portion was determined when the thickness H1 of the support substrate was changed to 100 μm, 200 μm, 400 μm, 600 μm, and 1000 μm in a state where the above was applied. The experimental results are shown in FIG.

The “position” shown in FIG. 10 refers to the bonding position of the side surface of the anchor portion shown in FIG. 9 with the supporting substrate (the substrate on which the force is directly applied) as the reference position 0, and points upward from this reference position 0 Point to the side position of the anchor part.

As shown in FIG. 10, it was found that the maximum stress acting on the anchor portion decreases as the thickness H1 of the support substrate increases. In addition, it was also found that the stress acting on the anchor portion becomes larger as the thickness H1 of the support substrate further moves upward from the reference position 0 and approaches the cap substrate.

FIG. 11 is a graph in which the maximum stress of the anchor portion at a position (corresponding to the bonding position with the cap substrate) separated upward by 20 μm from the reference position 0 is plotted for each thickness H1 of each supporting substrate. From the experimental results in FIG. 11, the ratio of the thickness H1 of the support substrate to the thickness H2 (20 μm) of the functional layer is 10 to 30 times the anchor portion by making the ratio of 10 to 30 It has been found that the maximum stress acting can be reduced. Thus, by restricting the substrate thickness of the MEMS sensor in which the upper and lower portions of the anchor portion are fixedly supported by the substrate, it is possible to suppress a defect such as breakage from the anchor portion even if a force due to an external factor or the like is applied. It has been found that stable and highly accurate detection characteristics can be obtained.

(Experiment of material and thickness of support substrate and cap substrate)
A simulation experiment was conducted using a laminated substrate in which a support substrate (first substrate) made of silicon, a functional layer made of silicon, and a cap substrate (second substrate) made of silicon shown in FIG. 12 are stacked. The functional layer has a structure of an anchor portion as shown in FIG. 12, and is fixed and supported on both the support substrate side and the cap substrate side.

Further, both the experiment in which the supporting substrate, the functional layer and the cap substrate were all formed of silicon and the experiment in which the supporting substrate and the functional layer were formed of silicon with a cap substrate were performed.

In addition, a first bonding layer (1 μm in thickness) made of silicon oxide is interposed between the support substrate and the functional layer, and an insulating oxide layer made of silicon oxide, the first layer of aluminum-germanium is formed between the functional layer and the cap substrate. The experiment was conducted on the assumption that the two bonding layers (the combined thickness of the oxide insulating layer and the second bonding layer is 1 μm) intervened (see FIGS. 2 and 3 for the structure).

Here, the linear expansion coefficient (22 ° C.) of silicon is 2.60 × 10 ⁻⁶ , the Young's modulus is 150 GPa, the Poisson's ratio is 0.17, and the linear expansion coefficient (22 ° C.) of glass is 3.25 × 10 ⁻⁶ , The Young's modulus was 63 GPa, the Poisson's ratio was 0.25, the linear expansion coefficient (22 ° C.) of silicon oxide was 0.56 × 10 ^-6 , the Young's modulus was 72 GPa, and the Poisson's ratio was 0.25.

In the experiment, the thickness H1 of the support substrate was fixed at 200 μm, and the thickness H2 of the functional layer was fixed at 20 μm. In addition, the width dimension of the supporting substrate and the cap substrate is 0.5 mm, and the length dimension orthogonal to the width dimension is 0.5 mm. Then, assuming that the strain in the initial state (25 ° C.) is 0, the thickness H 3 of the cap substrate made of silicon or glass is changed to 100 μm, 200 μm, 300 μm while giving a temperature change of ± 25 ° C. The position in the direction (plane direction) was determined.

Here, “position in the X direction” refers to the bonding position of the side surface of the anchor portion with the supporting substrate (in fact, the bonding position with the first bonding layer) as the reference position 0 as shown in FIG. It is shown by the side position to the X direction of the anchor portion at each height position from the reference position 0 toward the upper direction (direction toward the cap substrate).

FIG. 14 shows the relationship between the position in the X direction of the anchor portion and the height position. As shown in FIG. 14, it was found that when the cap substrate is made of glass, the position of the anchor portion in the X direction gradually increases as the position away from the reference position 0. In addition, it was found that when the cap substrate is made of silicon, the position of the anchor portion in the X direction slightly fluctuates, but this is not so much as when the cap substrate is made of glass.

Subsequently, from the above experimental results, the position of the anchor portion in the X direction at the height position separated from the reference position 0 at each thickness of the cap substrate by 20 μm (the bonding position with the cap substrate) Position in the X direction, that is, the maximum amount of deformation of the anchor portion in the X direction was determined. The experimental results are shown in FIG.

Further, FIG. 16 shows the reference position 0, the height position separated by 10 μm from the reference position 0, and the height position separated by 20 μm from the reference position 0 with respect to the thickness H3 of each cap substrate when the cap substrate is glass. It is the graph which plotted the position to the X direction in.

Further, FIG. 17 shows the reference position 0, the height position separated by 10 μm from the reference position 0, and the height position separated by 20 μm from the reference position 0 with respect to the thickness H3 of each cap substrate when the cap substrate is silicon It is the graph which plotted the position to the X direction in.

From the above experimental results, it was found that when the cap substrate is formed of the same silicon as the support substrate, the amount of deformation of the anchor portion in the X direction becomes very small. On the other hand, when the cap substrate is made of glass, the amount of deformation of the anchor portion in the X direction is larger than when the cap substrate is made of silicon, but when the cap substrate is 200 μm the same as the support substrate, the anchor portion is most It was found that the amount of deformation of can be reduced.

From the above experiment, it was found that it is preferable to form the cap substrate and the support substrate of the same material. At this time, the film thickness difference between the cap substrate and the support substrate is preferably within 100 μm, and the thickness of the cap substrate and the thickness of the support substrate are preferably set to be the same. Preferably, the cap substrate and the support substrate are formed of silicon.

It has also been found that the cap substrate may be formed of glass, the support substrate may be formed of silicon, and the cap substrate and the support substrate may be set to the same thickness.

As described above, the amount of deformation of the anchor portion due to the thermal stress can be reduced, and stable and highly accurate detection accuracy can be obtained.

H1 thickness of supporting substrate (first substrate) H2 thickness of functional layer H3 thickness of cap substrate (second substrate) 1 supporting substrate 2 functional layer 3

first bonding layer

4, 16, 17, 18 sensor unit 5 10, 23, 25, 33, 33, 42, 42, 52, 54 Anchor portion 11 Frame layer 12 Cap member 13 Cap substrate 14 Insulating layer 15 Second bonding layer 20 Sensor unit 35 Lead layer 50 External connection pad 56 First Metal layer 57 second metal layer

Claims

A functional layer having a first substrate, a sensor portion, and an anchor portion integrally formed with the sensor portion, and a first bonding layer formed of an insulating material for bonding between the anchor portion and the first substrate , And the sensor unit is spaced apart from the first substrate,
A MEMS sensor, wherein a thickness of the first substrate is formed in a range of 10 times to 30 times a thickness of the functional layer.
It has a second substrate opposed to the first substrate via the functional layer,
The sensor unit according to claim 1, wherein the sensor unit is disposed at a distance from the first substrate and the second substrate, and the anchor unit is fixed and supported via the second substrate and the second bonding layer. MEMS sensor.
The MEMS sensor according to claim 2, wherein the first substrate and the second substrate are formed of the same material.
The MEMS sensor according to claim 3, wherein the first substrate and the second substrate are formed to have the same thickness.
The MEMS sensor according to claim 3, wherein the first substrate and the second substrate are formed of silicon.
The MEMS sensor according to claim 2, wherein one of the first substrate and the second substrate is formed of silicon and the other is formed of glass, and the first substrate and the second substrate are formed to have the same thickness.
An insulating layer is provided on the surface of the second substrate facing the first substrate, the second bonding layer is formed of a metal bonding layer, and the lead layer connected to the second bonding layer is The MEMS sensor according to any one of claims 2 to 6, wherein the MEMS sensor is embedded in the insulating layer.
An insulating layer is provided on the surface opposite to the surface facing the first substrate of the second substrate, the second bonding layer is formed of a bonding layer of metal, and the second bonding layer and the second bonding layer are formed. The MEMS sensor according to any one of claims 2 to 6, wherein a lead layer connected via a through wiring layer formed separately from the substrate is embedded in the insulating layer.
The MEMS sensor according to any one of claims 1 to 8, wherein the first substrate and the functional layer are both formed of silicon.