JP2010156591A - Mems sensor and method for manufacturing mems sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MEMS sensor which has a high designing flexibility for attaining further miniaturization or relaxation of a stress of a beam part, without increasing the rigidity of the beam part, while maintaining sensitivity. <P>SOLUTION: The MEMS sensor is provided with: a frame-shaped support part; a plurality of beam parts extending inside the support part; weight parts disposed inside the support part and opposed to the beam parts with a space between; a plurality of coupling parts each of which is connected with the tip portion of the beam part and with a connecting area of the weight part differing each from others and couples the weight part with each of the beam parts in a plurality; and detecting means which are provided in the beam parts and detect deformation of the beam parts, due to the movement of the weight parts. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a MEMS (Micro Electro Mechanical Systems) sensor and a method for manufacturing the MEMS sensor.

Conventionally, MEMS sensors, such as an acceleration sensor, a vibration gyroscope, a pressure sensor, a vibration sensor, a microphone, and a force sensor, which convert a displacement of a beam portion to which a weight portion is connected into an electric signal are known (Patent Document 1). To 6). In Patent Documents 1 to 4, when a structure in which a beam part and a weight part are opposed to each other with a gap between them is adopted for a MEMS sensor, the beam part is compared with a case where the structure described in Patent Documents 5 and 6 is adopted. The size can be reduced while maintaining the sensitivity without increasing the rigidity.
JP-A-8-274349 JP-A-8-248061 Japanese Patent Laid-Open No. 9-15257 JP-A-6-342006 JP 2000-199714 A Japanese Patent No. 3303379

  However, as described in Patent Documents 1 to 4, in the structure in which the beam part is connected to one part of the weight part, the beam part is further reduced in size while maintaining the sensitivity without increasing the rigidity of the beam part, or the stress of the beam part is reduced. Even when trying to relax, the degree of freedom in design is low.

  It is an object of the present invention to provide a MEMS sensor having a high degree of freedom in designing for further downsizing or relaxing the stress of the beam part while maintaining the sensitivity without increasing the rigidity of the beam part.

  (1) A MEMS sensor for achieving the above object includes a frame-shaped support portion, a plurality of beam portions extending from the support portion to the inside of the support portion, and a gap disposed inside the support portion. A plurality of weight portions facing the plurality of beam portions, and a tip portion of the beam portion and a coupling region different from each other, and the weight portions are coupled to the plurality of beam portions. A plurality of connecting portions, and detection means for detecting deformation of the beam portions accompanying movement of the weight portions provided on the beam portions.

  According to the present invention, the MEMS sensor can be miniaturized while maintaining the sensitivity without increasing the rigidity of the beam portion by making the weight portion and the beam portion face each other with the gap interposed therebetween. In addition, according to the present invention, since a plurality of beam portions are connected to different coupling regions of the weight portion, a design for further downsizing or relaxing the stress of the beam portion while maintaining sensitivity without increasing rigidity. The degree of freedom increases.

(2) The MEMS sensor for achieving the above object may include one or more sets of the beam portions extending from the support portion so as to cross each other.
A pair of beams connected to different coupling regions of the weight can extend from the support until they cross each other. Extending the beam part from the support part until it crosses each other makes the MEMS sensor even smaller, while maintaining the sensitivity without increasing the rigidity of the beam part, compared to a configuration in which multiple beam parts are connected to one part of the weight part. Can be

(3) In the MEMS sensor for achieving the above object, the plurality of beam portions may extend straight from the support portion in different directions at equal angular intervals on the same plane.
When this configuration is adopted, when the beam portion expands and contracts due to the thermal stress, the weight portion is rotated to relieve the thermal stress.

  (4) In the MEMS sensor for achieving the above object, the plurality of beam portions may have the same length and may be arranged at intervals of 90 degrees.

(5) In the MEMS sensor for achieving the above object, the coupling region may be in a peripheral region of the weight portion.
In the case of adopting this configuration, even if the position of the coupling region with respect to the center of gravity of the weight portion is shifted, the influence on the motion characteristics of the weight portion is suppressed.

(6) In the MEMS sensor for achieving the above object, the plurality of beam portions may be bent on the same plane and arranged in a spiral shape.
When this configuration is adopted, the MEMS sensor can be further miniaturized while maintaining the sensitivity without increasing the rigidity of the beam portion as compared with the configuration in which the beam portion is straight. Further, in this case, when the beam portion is expanded and contracted by the thermal stress, the weight portion is rotated, so that the thermal stress is relieved.

(7) In the MEMS sensor for achieving the above object, the plurality of beam portions may be each spirally bent on the same plane.
When this configuration is adopted, the MEMS sensor can be further miniaturized while maintaining the sensitivity without increasing the rigidity of the beam portion as compared with the configuration in which the beam portion is straight.

(8) In the MEMS sensor for achieving the above object, the support portion, the beam portion, and the connection portion include a thick silicon layer and a thin silicon layer facing the thick silicon layer with a gap interposed therebetween. Formed in a laminated structure including a stopper layer that is different from silicon oxide through the thin silicon layer and in contact with the thick silicon layer, the weight portion includes the thick silicon layer,
The beam portion includes the thin silicon layer, the support portion includes the thick silicon layer, the stopper layer, and the thin silicon layer, and at least a surface layer of the connection portion includes the stopper layer.
When this configuration is adopted, a gap between the beam portion and the weight portion can be formed by selectively etching a layer made of silicon oxide between the thick silicon layer and the thin silicon layer, and the connecting portion. Since the etching end point can be controlled by this, variation in characteristics of the MEMS sensor can be suppressed. Here, the term “heterogeneity” refers to a property in which silicon oxide can be selectively removed at a low rate of removal with respect to at least silicon oxide in the step of etching silicon oxide.

(9) A MEMS sensor manufacturing method for achieving the above object includes a thick silicon layer, a thin silicon layer, and a silicon oxide layer sandwiched between the thick silicon layer and the thin silicon layer. A plurality of first holes as through holes and a second hole as a through hole are formed in the thin silicon layer and the silicon oxide layer of the wafer, and the silicon oxide is formed inside the first hole and the second hole. A layer different from the layer is laminated, and a first continuous region in contact with the stopper layer exposed from a plurality of the first holes and an annular shape in contact with the stopper layer exposed from the second holes and surrounding the first continuous region The thick silicon layer is etched in an annular region between the second continuous region and a weight portion is formed in the first continuous region, and the weight portion is opposed to the weight portion with the silicon oxide layer interposed therebetween. In one hole Wherein forming the beam portion in each of a plurality of regions of the thin silicon layer is removed by etching the silicon oxide layer from between the weight portion and the beam portion while leaving the stopper layer that includes.
According to the present invention, by removing the silicon oxide layer by etching, the weight portion and the beam portion can be opposed to each other with the gap therebetween. Therefore, the MEMS sensor can be reduced in size while maintaining the sensitivity without increasing the rigidity of the beam portion. Further, according to the present invention, when the silicon oxide layer is removed by etching, the end point can be controlled by the stopper layer, so that variations in characteristics of the MEMS sensor can be suppressed. In addition, according to the present invention, since a plurality of beam portions are connected to different regions of the weight portion, the degree of freedom in designing for further downsizing and relaxing the stress of the beam portion while maintaining the sensitivity without increasing the rigidity. Becomes higher.

  The order of the operations described in the claims is not limited to the order of description as long as there is no technical obstruction factor, and may be executed at the same time, may be executed in the reverse order of the description order, or may be continuous. It does not have to be executed in order. In particular, the expression that “a beam portion is formed in each of the plurality of regions of the thin silicon layer facing the weight portion and sandwiching the silicon oxide layer” is formed after the weight portion is formed. This is an expression that includes forming a beam portion in a region that faces the weight portion when the weight portion is formed. That is, forming the weight portion after forming the beam portion is also possible by “forming the beam portion in each of the plurality of regions of the thin silicon layer facing the weight portion and reaching the through hole with the silicon oxide layer interposed therebetween. To be included.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the corresponding component in each figure, and the overlapping description is abbreviate | omitted.
1. 1st Embodiment The angular velocity sensor which is 1st embodiment of the MEMS sensor of this invention is shown to FIG. 1A, FIG. 1B, and FIG. 1C. 1B and 1C are cross-sectional views showing the angular velocity sensor 1, and are cross-sectional views taken along the lines BB and CC shown in FIG. 1A, respectively. In FIG. 1B and FIG. 1C, the interface of the layer which comprises the angular velocity sensor 1 is shown with the broken line, and the boundary of the functional element which comprises the angular velocity sensor 1 is shown with the continuous line.

The angular velocity sensor 1 is a vibrating gyroscope for detecting three-axis angular velocity components orthogonal to each other. The angular velocity sensor 1 includes the laminated structure shown in FIG. 1 including a thick silicon layer 11, a thin silicon layer 13, an insulating layer 20, a stopper layer 30, electrode layers 81 and 83, and a piezoelectric layer 82. Yes. The stacked structure shown in FIG. 1 is accommodated in a package (not shown). Both the thick silicon layer 11 and the thin silicon layer 13 are made of single crystal silicon. The thickness of the thick silicon layer 11 is 625 μm. The thickness of the thin silicon layer 13 is 10 μm. A gap G is formed between the thick silicon layer 11 and the thin silicon layer 13. The insulating layer 20 is made of silicon oxide (SiO ₂ ). The thickness of the insulating layer 20 is 0.5 μm. The stopper layer 30 penetrates the thin silicon layer 13. The stopper layer 30 is made of polycrystalline silicon. The electrode layers 81 and 83 are made of platinum (Pt). The electrode layers 81 and 83 have a thickness of 0.1 μm. The piezoelectric layer 82 is made of PZT (lead zirconate titanate). The thickness of the piezoelectric layer 82 is 3 μm.

  The laminated structure of the angular velocity sensor 1 includes a frame-shaped support portion S, four beam portions F having fixed ends coupled to the inside of the support portion S, a weight portion M, and a weight portion M on the beam portion F. The connecting portion 31 that suspends the rod, the detecting piezoelectric element 80a and the driving piezoelectric element 80b provided on the beam portion F are formed as functional elements.

  The support part S has a form of a frame whose inner periphery is a square. The support S includes a thick silicon layer 11, a thin silicon layer 13, a stopper layer 30 and an insulating layer 20. Since the support portion S is fixed to a package (not shown), it substantially behaves as a rigid body. In the support portion S, the stopper layer 30 penetrates the thin silicon layer 13 and is in contact with the thick silicon layer 11 and the insulating layer 20. That is, in the support portion S, the stopper layer 30 connects the thin silicon layer 13 and the insulating layer 20 to the thick silicon layer 11. A region of the stopper layer 30 that connects the thin silicon layer 13 and the insulating layer 20 to the thick silicon layer 11 is referred to as a stopper portion 32. As shown in FIG. 1A, the pattern of the stopper portion 32 may be an annular shape that circulates around the support portion S, or may include a plurality of portions that are scattered on the support portion S. In FIG. 1A, the pattern of the stopper portion 32 is indicated by broken line hatching.

  Each of the four beam portions F has the same configuration (the same length, the same width, the same thickness, and the same contour) extending from the support portion S to the inside of the support portion S. Here, the orthogonal coordinate axis xyz is determined so that the xy plane is parallel to the plane on which the four beam portions F are arranged. The four beam portions F extend from the support portion S in four directions (x-axis positive direction, y-axis negative direction, x-axis negative direction, and y-axis positive direction) at an interval of 90 degrees, and face the weight M and the z-axis direction. is doing. A gap G having a constant height is formed between the beam portion F and the weight portion M. The beam portion F behaves as a cantilever beam having flexibility. Since the support portion S behaves as a rigid body, the end of the beam portion F connected to the support portion S becomes a fixed end in the coordinate system fixed to the angular velocity sensor 1.

The beam portions F ₁ and F ₃ extend straight from the support portion S in a direction parallel to the x-axis. The beam portions F ₁ and F ₃ extend from the support portion S until they cross each other. More specifically, the beam portions F ₁ and F ₃ extend in opposite directions (x-axis positive direction and x-axis negative direction) from two sides of the beam portion F facing in the x-axis direction. Each of the beam portions F ₁ and F ₃ has a length in which each tip exceeds the center of the weight portion M in the x-axis direction. The lengths of the beam portions F ₁ and F ₃ are longer than one half of the length of the weight portion M in the x-axis direction. The tip of the beam portion F ₁ is opposed to the beam portion F ₃ in the direction of the y-axis shown in FIG. 1, the distal end of the beam portion F ₃ faces the beam portion F ₁ in the direction of the y-axis shown in FIG.

The beam portions F ₂ and F ₄ extend straight from the support portion S in a direction parallel to the y-axis. The beam portions F ₂ and F ₄ extend from the support portion S until they cross each other. More specifically, the beam portions F ₂ and F ₄ extend in opposite directions (y-axis positive direction and y-axis negative direction) from two sides of the beam portion F facing in the y-axis direction. Each of the beam portions F ₂ and F ₄ has a length in which each tip exceeds the center of the weight portion M in the y-axis direction. The lengths of the beam portions F ₂ and F ₄ are longer than one half of the length of the weight portion M in the y-axis direction. The tip of the beam portion F ₂ is opposed to the beam portion F ₄ in the direction of the x-axis, the tip of the beam portion F ₄ faces the beam portion F ₂ in the direction of the x-axis.

  Each beam portion F includes a thin silicon layer 13 and an insulating layer 20. The thickness of the beam portion F is the sum of the thickness of the thin silicon layer 13 and the thickness of the insulating layer 20. The stopper layer 30 penetrates the thin silicon layer 13 at the tip of each beam portion F. A portion of the stopper layer 30 that penetrates the thin silicon layer 13 at the tip of the beam portion F constitutes a connecting portion 31. In FIG. 1A, the pattern of the connecting portion 31 is indicated by broken line hatching.

  The weight part M has the form of a plate whose outer periphery is rectangular. Since the weight part M consists of the thick silicon layer 11, it behaves substantially as a rigid body.

  The four connecting portions 31 connect the tip ends of the four beam portions F and the weight portions M at four locations. That is, each of the connecting portions 31 having one end connected to the tip ends of the four beam portions F has the other end connected to a different region (joining region) of the weight M. The four coupling regions where the four connecting portions 31 are coupled to the weight portion M are all in the peripheral region of the weight portion M. More specifically, the z-axis passes through the point where the line passing through the center of the weight M in the x-axis direction and parallel to the y-axis intersects with the line passing through the center of the weight M in the y-axis direction and parallel to the x-axis. In the region closer to the side surface of the weight part M than the parallel axis (this point is referred to as the central axis of the weight part M), the four connecting parts 31 are coupled to the weight part M.

  Since the weight portion M is coupled only to the four beam portions F and is disposed away from a package (not shown), the weight portion M moves in a coordinate system fixed to the angular velocity sensor 1. The four beam portions F move together with the weight portion M in a coordinate system fixed to the angular velocity sensor 1. That is, the four beam portions F are deformed as the weight portion M moves.

  As described above, the direction in which the four beam portions F extend from the support portion S goes around the inside of the support portion S in one direction at intervals of 90 degrees. The four connecting portions 31 that connect the four beam portions F and the weight portion M are centered on the central axis of the weight portion M and are spaced from the central axis of the weight portion M at intervals of 90 degrees around the weight portion M. Arranged in the distance area. Accordingly, when the four beam portions F extend, the weight portion M rotates in the clockwise direction in FIG. 1A. When the four beam portions F contract, the weight portion M rotates in the counterclockwise direction in FIG. 1A. That is, the stress for stretching each beam portion F is reduced by the weight portion M rotating in the clockwise direction in FIG. 1A. And the stress which contracts each beam part F reduces by the weight part M rotating in the counterclockwise direction in FIG. 1A. Further, since the weight part M and the beam part F are connected to each other at a plurality of locations around the weight part M, compared to a structure in which the weight part M and the beam part F are connected at one place on the central axis of the weight part M. Even if the connecting position of the weight part M and the beam part F is shifted with respect to the center of gravity of the weight part M, the influence on the motion characteristics of the weight part M is suppressed.

  Each beam portion F is provided with a driving piezoelectric element 80b for exciting the weight portion M by bending the beam portion F. The driving piezoelectric element 80 b is provided on the surface of the beam portion F in the vicinity of the fixed end of the beam portion F. For this reason, when the driving piezoelectric element 80b expands and contracts, the distal end portion of the beam portion F vibrates. The weight part M can be moved around by applying alternating excitation voltages having different phases to the four driving piezoelectric elements 80b.

  Each beam portion F is provided with a detecting piezoelectric element 80a as a detecting means for detecting deformation of the beam portion F. The detection piezoelectric element 80 a is provided on the surface of the beam portion F in the vicinity of the free end of the beam portion F. The distortion accompanying the deformation of the beam portion F is concentrated in the vicinity of the boundary between the flexible beam portion F and the connecting portion 31 and the support portion S that behave as a substantially rigid body. For this reason, when the beam portion F is deformed with the movement of the weight portion M, the detecting piezoelectric element 80a expands and contracts. When the angular velocity sensor 1 rotates while the weight portion M is in a circular motion, AC voltage signals corresponding to the Coriolis force acting on the weight portion M are output from the four detection piezoelectric elements 80a. By removing the excitation component from this voltage signal, the angular velocity component of the xyz axis of the angular velocity sensor 1 can be obtained.

  According to the present embodiment, the ratio of the length of the beam portion F to the outer dimension of the angular velocity sensor 1 is increased by making the weight portion M and the beam portion F face each other with a gap therebetween. And the ratio of the length of the beam part F with respect to the external dimension of the support part S is further raised by connecting the beam part F and the weight part M by the some connection part 31 in a different area | region for every beam part F. FIG. More specifically, the beam portion F is extended by extending the beam portion F until a pair of beam portions F extending in opposite directions from each other on opposite sides of the support portion S cross each other. Thus, by increasing the ratio of the length of the beam portion F, the angular velocity sensor 1 can be reduced in size while maintaining the sensitivity and the dynamic range without increasing the rigidity of the beam portion F. Further, by making the beam portion F longer, it is possible to suppress variations in the characteristics of the angular velocity sensor 1 due to manufacturing tolerances.

2. Second Embodiment As shown in FIG. 2, the beam portion F may be arranged in a spiral shape inside the support portion S. Specifically, it is as follows. In this embodiment, the inner periphery of the support part S and the outer periphery of the weight part M are circular. The four beam portions F are arranged on the same plane parallel to the xy plane. The direction in which the beam portion F extends from the support portion S is closer to the tangential direction of the inner periphery of the support portion S as it is closer to the fixed end, and away from the tangential direction of the inner periphery of the support portion S as it is closer to the free end. The four beam portions F are bent in an arc shape. The direction in which each beam portion F protrudes from the support portion S at the boundary with the support portion S (shown by a broken line in FIG. 2) circulates in one direction around the inside of the support portion S at intervals of 90 degrees. is doing. The four connecting portions 31 that connect the four beam portions F and the weight portion M are equidistant from the central axis of the weight portion M at intervals of 90 degrees around the central portion of the weight portion M. Is located in the area. For this reason, the stress which expands / contracts each beam part F reduces when the weight part M rotates.

  In addition, since the ratio of the length of the beam portion F to the outer dimension of the support portion S can be increased by bending the beam portion F, the angular velocity sensor is maintained while maintaining the sensitivity and dynamic range without increasing the rigidity of the beam portion F. 2 can be reduced in size. Also, by making the beam portion F longer, it is possible to suppress variations in the characteristics of the angular velocity sensor 2 due to manufacturing tolerances.

3. Third Embodiment As shown in FIG. 3, the beam portion F may be arranged in a spiral shape inside the support portion S. Specifically, it is as follows. In this embodiment, the inner periphery of the support part S and the outer periphery of the weight part M are square. The four beam portions F are arranged on the same plane parallel to the xy plane. The beam portion F projects in the vertical direction from the vicinity of the respective end portions of the four sides inside the support portion S, and is bent at a right angle toward the inside of the weight portion M at the intermediate portion. The direction in which each beam portion F protrudes from the support portion S at the boundary with the support portion S (shown by a broken line in FIG. 3) circulates in one direction around the inside of the support portion S at intervals of 90 degrees. is doing. The four connecting portions 31 that connect the four beam portions F and the weight portion M are equidistant from the central axis of the weight portion M at intervals of 90 degrees around the central portion of the weight portion M. Is located in the area. For this reason, the stress which expands / contracts each beam part F reduces when the weight part M rotates.

  In addition, since the ratio of the length of the beam portion F to the outer dimension of the support portion S can be increased by bending the beam portion F, the angular velocity sensor is maintained while maintaining the sensitivity and dynamic range without increasing the rigidity of the beam portion F. 3 can be reduced in size. Also, by making the beam portion F longer, it is possible to suppress variations in the characteristics of the angular velocity sensor 3 due to manufacturing tolerances.

4). Fourth Embodiment As shown in FIG. 4, the beam portions F may be bent in a spiral shape on the same plane. Specifically, it is as follows. In this embodiment, in this embodiment, the inner periphery of the support part S and the outer periphery of the weight part M are square. The four beam portions F are arranged on the same plane parallel to the xy plane. The four beam portions F are extended by two from two opposite sides inside the support portion S. That is, the beam portions F ₁ and F ₄ protrude from the vicinity of both ends of one side inside the support portion S toward the opposite side. Beam portion _F 2, _{F 3} protrudes toward the side of the beam portion _F 1, the beam portion from the opposite side of _the side _{F 4} are attached _F 1, _{F 4} is attached. The four beam portions F are each bent in a spiral shape inside the mutually exclusive regions obtained by dividing the inside of the support portion S into four. The four connecting portions 31 that connect the four beam portions F and the weight portion M are equidistant from the central axis of the weight portion M at intervals of 90 degrees around the central portion of the weight portion M. Is located in the area.

By bending the beam portion F in a spiral shape, the ratio of the length of the beam portion F to the outer dimension of the support portion S can be further increased, so that the sensitivity and dynamic range can be maintained without increasing the rigidity of the beam portion F. However, the angular velocity sensor 4 can be further reduced in size. In addition, by making the beam portion F longer, it is possible to further suppress variations in the characteristics of the angular velocity sensor 4 due to manufacturing tolerances.
A plurality of detection piezoelectric elements 80a may be arranged for one beam portion F, or a plurality of driving piezoelectric elements 80b may be arranged for one beam portion.

5). Manufacturing Method Hereinafter, a manufacturing method of the angular velocity sensors 1 to 4 will be described with reference to FIGS. The angular velocity sensors 1 to 4 can be manufactured by substantially the same method only by changing the pattern of each layer constituting the laminated structure. 5 to 9, FIG. 13A, and FIG. 14A are cross-sectional views corresponding to the line BB shown in FIG. 1A. 10 to 12, 13B, and 14B are cross-sectional views corresponding to the CC line shown in FIG. 1A.

First, as shown in FIG. 5, an SOI (Silicon On Insulator) wafer 10 in which a thick silicon layer 11, a silicon oxide layer 12, and a thin silicon layer 13 are stacked is prepared, and etching is performed using a protective film R1 made of a photoresist. A first hole H1 and a second hole H2 penetrating the thin silicon layer 13 and the silicon oxide layer 12 are formed. The first hole H <b> 1 is a through hole serving as a mold for forming the connecting portion 31. The second hole H2 is a through hole serving as a mold for forming the stopper portion 32. Therefore, when forming the laminated structure (die) of the angular velocity sensor 1 exemplified in the first embodiment, four first holes H1 are formed and four second holes H2 are formed for each region cut as one die. One is formed in an annular shape surrounding the first hole H1. The SOI wafer 10 includes a thick silicon layer 11 made of single crystal silicon having a thickness of 625 μm, a silicon oxide layer 12 made of silicon dioxide (SiO ₂ ) having a thickness of 1 μm, and a thin silicon layer made of single crystal silicon having a thickness of 10 μm. Reference numeral 13 denotes wafers stacked in this order.

Next, as shown in FIG. 6, a film different from the silicon oxide layer 12 is grown on the surface of the thick silicon layer 11 and the surface of the thin silicon layer 13 exposed from the first hole H1 and the second hole H2. A stopper layer 30 that completely fills the first hole H1 and the second hole H2 is formed. As a material for the stopper layer 30, a substance capable of selectively etching the silicon oxide layer 12 while leaving the stopper layer 30 and the silicon layers 11 and 13 can be selected. That is, it is possible to select a material having a small etching selection ratio of the stopper layer 30 and the silicon layers 11 and 13 to the silicon oxide layer 12. Specifically, for example, a polycrystalline silicon film having a thickness of 15 μm is formed as the stopper layer 30 by CVD. As the stopper layer 30, single crystal silicon may be epitaxially grown, another semiconductor film such as amorphous silicon or silicon germanium (SiGe) may be formed, silicon nitride (Si _x N _y ), or nitride A nitride film such as aluminum (Al _x N _y ) or titanium nitride (Ti _x N _y ) may be formed, or aluminum oxide (Al _x O _y ), tantalum oxide (TaO _x ), titanium oxide (TiO 2). _x ) or an oxide film such as tungsten silicide (WSi _x ), molybdenum silicide (MoSi _x ), titanium silicide (TiSi _x ), or a silicide compound film may be formed. A film of a metal such as copper (Cu), nickel (Ni), platinum (Pt), or gold (Au) may be formed.

  Next, as shown in FIG. 7, a film R <b> 2 for etch back is formed on the surface of the stopper layer 30. As the material of the protective film R2, a material that can have an etching selection ratio with the stopper layer 30 of approximately 1: 1 is selected. For example, a coating R2 having a flat surface is formed by applying and baking a photoresist, SOG (Spin On Glass), and polyimide.

  Next, as shown in FIG. 8, under the condition that the etching selectivity between the coating R2 and the stopper layer 30 is approximately 1: 1, the surface layer of the stopper layer 30 is etched back together with the coating R2 until the thin silicon layer 13 is exposed. To do. As a result, the surfaces of the thin silicon layer 13 and the stopper layer 30 are continuously flat, and the connecting portion 31 and the stopper portion 32 made of the stopper layer 30 are formed. Note that after the stopper layer 30 is formed, the surfaces of the thin silicon layer 13 and the stopper layer 30 may be made flat and continuous by grinding, polishing, or CMP (Chemical Mechanical Polishing).

Next, as shown in FIG. 9, the insulating layer 20 is formed on the surfaces of the thin silicon layer 13 and the stopper layer 30. As the insulating layer 20, a silicon dioxide film having a thickness of 0.5 μm is formed by, for example, thermal oxidation or CVD. A film such as PSG (Phospho Silicate Grass), BPSG (Boro-Phospho Silicate Grass), or silicon nitride (Si _x N _y ) may be formed as the insulating layer 20.

  Next, as shown in FIG. 10, the electrode layer 81, the piezoelectric layer 82, and the electrode layer 83 are laminated on the surface of the insulating layer 20 in this order. As the electrode layer 81, a platinum film having a thickness of 0.1 μm is formed by sputtering, for example. As the piezoelectric layer 82, a film of PZT (lead zirconate titanate) having a thickness of 3 μm is formed by, for example, sputtering. As the electrode layer 83, a platinum film having a thickness of 0.1 μm is formed by sputtering, for example.

  Next, as shown in FIG. 11, the electrode layer 83 and the piezoelectric layer 82 are patterned into a predetermined shape by etching using a protective film R3 made of a photoresist. At this time, the upper layer electrode of the driving piezoelectric element 80b and the detecting piezoelectric element 80a, its conducting wire, and the bonding pad are formed. For example, the electrode layer 83 and the piezoelectric layer 82 are anisotropically etched by a milling method using argon (Ar) ions.

  Next, as shown in FIG. 12, the electrode layer 81 is patterned into a predetermined shape by etching using a protective film R4 made of a photoresist. For example, the electrode layer 81 is anisotropically etched by a milling method using argon (Ar) ions. As a result, the driving piezoelectric element 80b and the detecting piezoelectric element 80a are formed. At this time, the lower layer electrodes of the driving piezoelectric element 80b and the detecting piezoelectric element 80a, the lead wires, and the bonding pads are formed.

Next, as shown in FIGS. 13A and 13B, the pattern of the beam portion F is formed by etching the insulating layer 20, the thin silicon layer 13 and the silicon oxide layer 12 using the protective film R5 made of photoresist. The pattern of the beam F is obtained by etching the insulating layer 20 by reactive ion etching using, for example, CHF ₃ gas, and then etching the thin silicon layer 13 by reactive ion etching using CF ₄ gas and O ₂ gas. Subsequently, the silicon oxide layer 12 is formed by etching by reactive ion etching using CHF ₃ gas. The insulating film 20 is wet etched using hydrofluoric acid or buffered hydrofluoric acid, the thin silicon layer 1 is wet etched using tetramethylammonium hydroxide (TMAH) or potassium hydroxide (KOH), and hydrofluoric acid or buffered hydrofluoric acid is further removed. Alternatively, the silicon oxide layer 12 may be wet etched.

Next, as shown in FIG. 14, the thick portion M is formed by etching the thick silicon layer 11. That is, first, as shown in FIG. 14A, the surface on which the insulating layer 20 is formed is temporarily bonded to the sacrificial substrate 99. As the adhesive layer 98, for example, a wax, a photoresist, a double-sided pressure-sensitive adhesive sheet, or the like is used. Next, a protective film R6 made of photoresist is formed on the surface of the thick silicon layer 11, and an annular groove 11t is formed by anisotropic etching using the protective film R6, thereby forming the weight portion M inside the annular groove 11t. To do. The annular groove 11t is formed in an annular region that surrounds the four connecting portions 31 so that the weight portion M contacts all of the four connecting portions 31. More specifically, the thick silicon layer 11 is anisotropically formed by Deep-RIE (so-called Bosch process) in which the steps of passivation using C ₄ F ₈ plasma and etching using SF ₆ plasma are alternately repeated at short time intervals. Is etched. Note that this step of forming the weight portion M may be performed as the first step of processing the SOI wafer 10 or may be performed immediately after the insulating layer 20 is formed.

  Next, the workpiece is peeled from the sacrificial substrate 99, the silicon oxide layer 12 is selectively removed by isotropic etching, and dicing is performed to complete the laminated structure of the angular velocity sensor 1 shown in FIG. By removing the silicon oxide layer 12 by isotropic etching, a gap G between the thick silicon layer 11 and the thin silicon layer 13 is formed, and the weight part M and the beam part F face each other with the gap G interposed therebetween. . At this time, since the connecting portion 31 made of the stopper layer 30 different from the silicon oxide layer 12 and the stopper portion 32 itself act as an etching stopper, the etching end point of the silicon oxide layer 12 is accurately controlled. Therefore, since the shapes of the weight part M, the connecting part 31, and the beam part F are accurately formed, the angular velocity sensor 1 with small variations in characteristics can be manufactured.

6). Other Embodiments The technical scope of the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the scope of the present invention. For example, a piezoresistive element may be used as a means for detecting the deformation of the beam portion F. The piezoresistive element is formed, for example, by doping a thin silicon layer 13 with impurity ions. Further, the present invention can be applied to a motion sensor that includes a piezoresistive element and a piezoelectric element as means for detecting deformation of the beam portion F and detects angular velocity and acceleration.

  In the present invention, since the stopper layer is used, the shape of the beam portion F can be freely designed. For this reason, the form of the beam part F is not limited to the above embodiment, and can be changed to various forms such as arranging all the beam parts F in a straight line or having three or four beam parts F. is there.

  Since the stopper layer only needs to be used for controlling the end point of etching, for example, the first hole H1 and the second hole H2 formed in the thin silicon layer 13 and the silicon oxide layer 12 are filled with two or more layers to form the connecting portion. Only the surface layer 31 may be configured as the stopper layer 30, and the connecting portion 31 that connects the weight portion M and the beam portion F may have a multilayer structure. In this case, the step coverage of the layer filling the first hole H1 and the second hole H2 may be improved by using a side spacer, and the generation of voids may be prevented.

  Of course, various constituent elements illustrated in different embodiments can be combined. In addition, the materials, dimensions, film forming methods, pattern transfer methods, and process orders shown in the above embodiment are merely examples, and those skilled in the art will understand the addition and deletion of processes and the replacement of process orders. It is omitted.

FIG. 1A is a top view according to the first embodiment of the present invention. FIG. 1B is a cross-sectional view according to the first embodiment of the present invention. FIG. 1C is a cross-sectional view according to the first embodiment of the present invention. The top view concerning a second embodiment of the present invention. The top view concerning a third embodiment of the present invention. The top view concerning 4th embodiment of the present invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. FIG. 13A is a cross-sectional view according to an embodiment of the present invention. FIG. 13B is a cross-sectional view according to an embodiment of the present invention. FIG. 14A is a cross-sectional view according to an embodiment of the present invention. FIG. 14B is a cross-sectional view according to an embodiment of the present invention.

Explanation of symbols

1: angular velocity sensor, 2: angular velocity sensor, 3: angular velocity sensor, 4: angular velocity sensor, 10: SOI wafer, 11: silicon layer, 11t: annular groove, 12: silicon oxide layer, 13: silicon layer, 20: insulating layer 30: stopper layer, 31: connecting portion, 32: stopper portion, 80a: piezoelectric element for detection, 80b: piezoelectric element for driving, 81: electrode layer, 82: piezoelectric layer, 83: electrode layer, 98: adhesive layer, 99: sacrificial substrate, F: beam portion, F ₁ : beam portion, F ₂ : beam portion, F ₃ : beam portion, F ₄ : beam portion, G: gap, H1: first hole, H2: second hole, M: weight part, R1: protective film, R2: coating, R2: protective film, R3: protective film, R4: protective film, R5: protective film, R6: protective film, S: support part

Claims (9)

A frame-shaped support,
A plurality of beam portions extending from the support portion to the inside of the support portion;
A weight portion disposed inside the support portion and opposed to the plurality of beam portions across a gap;
A plurality of connecting portions each coupled to a plurality of the beam portions coupled to the tip portions of the beam portions and the coupling portions different from each other;
Detecting means provided on the beam portion for detecting deformation of the beam portion accompanying the movement of the weight portion;
A MEMS sensor comprising: Comprising one or more sets of beam portions extending from the support portion until they cross each other;
The MEMS sensor according to claim 1. The plurality of beam portions extend straight from the support portion in different directions at equal angular intervals on the same plane.
The MEMS sensor according to claim 2. The plurality of beam portions have the same length and are arranged at intervals of 90 degrees.
The MEMS sensor according to claim 3. The coupling region is in a peripheral region of the weight portion;
The MEMS sensor as described in any one of Claim 1 to 4. The plurality of beam portions bend on the same plane and are arranged in a spiral shape,
The MEMS sensor according to claim 1. The plurality of beam portions are each spirally bent on the same plane,
The MEMS sensor according to claim 1. The support portion, the beam portion, and the connecting portion are formed by passing through a thin silicon layer facing the thick silicon layer with a gap between the thick silicon layer and the gap, and through the thin silicon layer and in contact with the thick silicon layer. Formed in a laminated structure including a stopper layer that is different from the object,
The weight portion includes the thick silicon layer,
The beam includes the thin silicon layer;
The support portion includes the thick silicon layer, the stopper layer, and the thin silicon layer,
At least the surface layer of the connecting portion is composed of the stopper layer.
The MEMS sensor according to any one of claims 1 to 7. A plurality of through holes in the thin silicon layer and the silicon oxide layer of the wafer including a thick silicon layer, a thin silicon layer, and a silicon oxide layer sandwiched between the thick silicon layer and the thin silicon layer Forming a first hole that is and a second hole that is a through hole,
Laminating a stopper layer different from the silicon oxide layer inside the first hole and the second hole,
An annular shape between a first continuous region in contact with the stopper layer exposed from the plurality of first holes and an annular second continuous region in contact with the stopper layer exposed from the second holes and surrounding the first continuous region Forming a weight portion in the first continuous region by etching the thick silicon layer in a region;
Forming a beam portion in each of the plurality of regions of the thin silicon layer facing the weight portion across the silicon oxide layer and reaching the first hole,
Removing the silicon oxide layer by etching from between the weight portion and the beam portion while leaving the stopper layer;
A method for manufacturing a MEMS sensor.

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