JP2010147268A - Mems sensor, and method of manufacturing mems sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MEMS sensor which hardly fractures and has superior shock resistance performance when a flexible portion deforms. <P>SOLUTION: The MEMS sensor includes: a support portion; the flexible portion which is a flexible film having one end coupled to the support portion and has a thick part and a thin part which has a gradual decrease section, a border between the thick part and the thin part being defined as an end of the section, thickness of the gradual decrease section decreasing as getting away from the thick part; and a strain detecting means formed at the thin portion to detect strain generated at the thin portion. <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.

MEMS sensors such as an acceleration sensor, an angular velocity sensor, a pressure sensor, a vibration sensor, a microphone, and a force sensor are provided with flexible portions such as beams and diaphragms. Patent Document 1 describes a MEMS sensor in which a bent portion is formed in a diaphragm.
JP-A-7-74370

  However, in the MEMS sensor described in Patent Document 1, when the diaphragm is deformed, stress concentrates on the bent portion formed in the diaphragm and is easily broken.

  The present invention was created in view of this problem, and an object of the present invention is to provide a MEMS sensor that is not easily broken when the flexible portion is deformed and has excellent impact resistance.

  (1) A MEMS sensor for achieving the above object is a flexible film in which a support part and one end are coupled to the support part, and a boundary between the thick part and the thick part is formed. A thin portion having a gradually decreasing section whose thickness gradually decreases as the end of the section is separated from the thick portion, a flexible portion that is arranged in a direction away from the one end, and a thin portion that is formed on the thin portion. Strain detection means for detecting the generated distortion.

  According to the present invention, since the thin part is formed in the flexible part, the flexible part can be made small without increasing the rigidity, so that the MEMS sensor can be downsized. In addition, since the stress due to the deformation of the flexible portion is distributed throughout the gradually decreasing section of the thin-walled portion, the flexible portion is hardly broken and the impact resistance performance is improved. In addition, when the flexible portion is deformed, the thin portion is more distorted than the thick portion. Therefore, by forming the strain detecting means in the thin portion, the detection sensitivity of the physical quantity accompanying the deformation of the flexible portion is increased. be able to.

  (2) The MEMS sensor for achieving the above object further includes a weight portion coupled to the other end of the flexible portion, wherein the thick portion and the thin portion are one end of the flexible portion and the other. It may be formed on a straight line connecting the ends.

  According to the present invention, even if the MEMS sensor includes a weight portion, the stress due to the deformation of the flexible portion is dispersed throughout the entire decreasing section, so that the flexible portion is hard to break and the impact resistance performance is improved. In addition, since the thick part and the thin part are formed on a straight line connecting one end and the other end of the flexible part, the flexible part is easily bent. Can be increased.

  (3) In the MEMS sensor for achieving the above object, the flexible portion is a beam having one end coupled to the support portion and the other end coupled to the weight portion, and the thin portion is connected to one end of the beam. You may cross two sides which connect an other end.

  According to the present invention, since the thin portion crosses between the two sides of the beam, the flexible portion is easily bent. Therefore, the detection sensitivity of the physical quantity accompanying the bending of the flexible portion can be increased.

  (4) In the MEMS sensor for achieving the above object, the flexible portion is an annular diaphragm having one end coupled to the support portion and the other end coupled to the weight portion, and the thin portion includes the diaphragm. You may go around.

  According to the present invention, since the diaphragm is easily bent when the thin-walled portion goes around, it is possible to increase the detection sensitivity of the physical quantity that accompanies the bending of the diaphragm.

  (5) In the MEMS sensor for achieving the above object, one of the principal surfaces of the flexible part may be flat and the other principal surface of the flexible part may be gently recessed in the thin part.

  According to the present invention, since it is not necessary to dent both main surfaces of the flexible part, it is possible to simplify the manufacturing process of the MEMS sensor that is difficult to break the flexible part and has excellent impact resistance, and to reduce the manufacturing cost. Moreover, since the dent of a thin part is gentle, a flexible part is hard to fracture | rupture and impact resistance performance improves. In addition, that the main surface is gently depressed means that the depression is formed by continuously changing the inclination of the main surface without bending the main surface. In this specification, the main surface of the flexible portion is a surface that spreads in the direction in which the film constituting the flexible portion spreads, and a plurality of films included in the laminated structure constituting the die of the MEMS sensor are laminated. A surface extending in a direction perpendicular to the direction in which it is formed.

  (6) A MEMS sensor for achieving the above object has a support part and a flexible film with one end coupled to the support part, and has a waveform section that gently swells in a direction away from the one end. A flexible portion; and strain detection means for detecting a strain formed in the waveform section and occurring in the waveform section.

  According to the present invention, since the flexible part has a corrugated section, the flexible part can be made small without increasing the rigidity, and thus the MEMS sensor can be downsized. Further, since the waviness of the corrugated section in the flexible portion is gentle, the flexible portion is hardly broken and the impact resistance performance is improved. In addition, when the flexible part is deformed, the waveform section is more strained than sections other than the waveform section in the flexible section. Therefore, forming the strain detection means in the waveform section causes deformation of the flexible section. The detection sensitivity of the physical quantity can be increased. In addition, the wavy wave section gently means that the two main surfaces in the waveform section are not bent and the inclination of the two main surfaces continuously changes while keeping the distance between each other basically constant. means.

  (7) In the MEMS sensor for achieving the above object, the MEMS sensor further includes a weight part coupled to the other end of the flexible part, and the corrugated section is gently in a direction from one end to the other end of the flexible part. You may swell.

  According to the present invention, even if the MEMS sensor includes a weight portion, the waviness of the corrugated section in the flexible portion is gentle, so that the flexible portion is hardly broken and the impact resistance performance is improved. In addition, since the wavy section undulates in the direction from one end of the flexible portion toward the other end, the flexible portion is easily bent, so that the detection sensitivity of the physical quantity accompanying the bending of the flexible portion can be increased. Moreover, since the waveform section is wavy in the direction from the one end to the other end of the flexible portion, the flexible portion is easily bent. Therefore, the detection sensitivity of the physical quantity accompanying the bending of the flexible portion can be increased.

  (8) In the MEMS sensor for achieving the above object, the flexible portion is a beam having one end coupled to the support portion and the other end coupled to the weight portion, and the corrugated section includes one end of the beam. You may cross two sides which connect an other end.

  According to the present invention, since the flexible section is easily bent when the corrugated section crosses between the two sides of the beam, the detection sensitivity of the physical quantity accompanying the bending of the flexible section can be increased.

  (9) In the MEMS sensor for achieving the above object, the flexible portion is an annular diaphragm having one end coupled to the support portion and the other end coupled to the weight portion, and the corrugated section includes the diaphragm. You may go around.

  According to the present invention, since the diaphragm is easily bent when the waveform section goes around, it is possible to increase the detection sensitivity of the physical quantity accompanied by the bending of the diaphragm.

  (10) A MEMS sensor manufacturing method for achieving the above-described object gently swells on the surface of the second silicon layer of an SOI wafer including a first silicon layer and a second silicon layer thinner than the first silicon layer. A support part that forms a wavefront and includes the first silicon layer; and a flexible film that has one end coupled to the support part and includes the second silicon layer and does not include the first silicon layer. Forming a flexible part having the wavefront gently undulating in a direction away from the part by removing a part of the first silicon layer, and the strain detecting means for detecting the strain of the flexible part. Forming in a section corresponding to the wavefront of the flexure.

  According to the present invention, since the wavefront undulation in the flexible portion is formed gently, it is possible to manufacture a MEMS sensor that is not easily broken and has excellent impact resistance. The gentle wavefront means that the slope of the surface is continuously changing without bending the surface.

  (11) In the method of manufacturing a MEMS sensor for achieving the above object, a heat-resistant protective film having a predetermined pattern is formed on the second silicon layer, and the second silicon located under the heat-resistant protective film The wavefront may be formed by thermally oxidizing a layer and selectively removing a thermally oxidized region of the second silicon layer.

  In the present invention, the wavefront of the flexible part is formed by a LOCOS (local oxidation of silicon) process. That is, according to the present invention, a gentle wavefront is formed on the surface of the second silicon layer serving as the flexible portion by isotropically diffusing oxygen by thermal oxidation.

  (12) In the MEMS sensor manufacturing method for achieving the above object, a protective film having a predetermined three-dimensional pattern is formed on the surface of the second silicon layer, and the second silicon layer is different from the protective film. The wavefront may be formed by isotropic etching.

  According to the present invention, since the pattern of the protective film is transferred to the second silicon layer by anisotropic etching together with the protective film, a gentle wavefront region can be formed in the flexible portion. In addition, since the protective film is etched together, the manufacturing process can be simplified and the manufacturing cost can be reduced.

  (13) In the method of manufacturing a MEMS sensor for achieving the above object, the protective film may be formed by exposure and development through a multi-tone mask.

  According to the present invention, by using a multi-tone mask, a protective film having a three-dimensional pattern can be formed by one exposure and development.

  (14) According to a method of manufacturing a MEMS sensor for achieving the above object, in a SOI wafer including a first silicon layer and a second silicon layer thinner than the first silicon layer, the surface of the second silicon layer gently swells. A wavefront region is formed, an epitaxial crystal silicon layer is epitaxially grown on a surface of the second silicon layer on which the wavefront region is formed, and a support portion including the first silicon layer and one end are coupled to the support portion. A flexible film that includes the epitaxial crystalline silicon layer and does not include the first silicon layer, and that gently undulates in a direction away from the support section and includes a corrugated section corresponding to the wavefront region; To detect distortion of the flexible part formed by selectively removing a part of the first silicon layer and a part of the second silicon layer The distortion detecting means is formed on the waveform segment comprises.

  According to the present invention, since the waviness of the corrugated section in the flexible portion is gently formed, a MEMS sensor that is hard to break and excellent in impact resistance can be manufactured. In addition, the wavy wave section gently means that the two main surfaces in the waveform section are not bent and the inclination of the two main surfaces continuously changes while keeping the distance between each other basically constant. means.

Hereinafter, embodiments of the present invention will be described in the following order 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. First embodiment (Configuration)
A six-axis motion sensor die 1A according to a first embodiment of the present invention is shown in FIGS. 1A, 1B, and 1C. The motion sensor 1 includes a package 1B shown in FIG. 2 and a die 1A accommodated in the package 1B, and detects a three-axis acceleration component orthogonal to each other and a three-axis angular velocity component orthogonal to each other. In FIG. 1B and FIG. 1C showing the BB line cross section and CC line cross section shown in FIG. 1A, the interface of the layers constituting the die 1A of the motion sensor 1 is indicated by broken lines, and the mechanical configuration constituting the die 1A of the motion sensor 1 Element boundaries are indicated by solid lines.

As shown in FIGS. 1B and 1C, the die 1A of the motion sensor 1 includes a thick silicon layer 101 as a first silicon layer, an etching stopper layer 102, a thin silicon layer 104 as a second silicon layer, and an insulating layer. 106, an electrode layer 108, 112, a piezoelectric layer 110, a surface insulating layer 114, and a surface wiring layer 115. The thickness of the thick silicon layer 101 made of single crystal silicon (Si) is 625 μm. The etching stopper layer 102 is made of a silicon oxide film (SiO ₂ ). The thickness of the etching stopper layer 102 is 1 μm. The thickness of the thin silicon layer 104 made of single crystal silicon is 10 μm. The insulating layer 106 is made of a silicon oxide film. The thickness of the insulating layer 106 is 300 nm. The electrode layers 108 and 112 are both made of platinum (Pt). The electrode layers 108 and 112 both have a thickness of 0.1 μm. The piezoelectric layer 110 is made of PZT (lead zirconate titanate). The thickness of the piezoelectric layer 110 is 3 μm. The surface insulating layer 114 is made of photosensitive polyimide. The surface insulating layer 114 has a thickness of 10 μm. The surface wiring layer 115 is made of aluminum (Al). The thickness of the surface wiring layer 115 is 0.5 μm.

  The die 1A of the motion sensor 1 includes a support portion S having a rectangular frame shape, four flexible portions F having one end coupled to the support portion S and arranged in a cross shape inside the support portion S, and four A weight part M coupled to the flexible part F, a piezoresistive element 40 as a strain detecting means, and a piezoelectric element P as a strain detecting means or a driving means are provided and accommodated in the package 1B.

  The support S includes a thick silicon layer 101, an etching stopper layer 102, a thin silicon layer 104, and an insulating layer 106. Since the support portion S includes a silicon layer 101 that is sufficiently thicker than the flexible portion F and is fixed to the package 1B, the support portion S behaves as a substantially rigid body that is stationary in a coordinate system fixed to the motion sensor.

  The flexible part F includes a thin silicon layer 104 and an insulating layer 106. The flexible portion F has one end coupled to the support portion S and the other end coupled to the weight portion M. Since the flexible portion F does not include the thick silicon layer 101, the flexible portion F behaves as a flexible film. The upper surface which is one of the main surfaces of the flexible portion F is gently undulating. That is, the upper surface of the flexible part F is gently recessed in the thin part 202. On the other hand, the lower surface which is the other main surface of the flexible part F is flat. Therefore, the thickness of the flexible part F is not constant in the direction from the support part S to the weight part M. That is, the flexible part F has a thick part 201 and a thin part 202 thinner than the thick part 201. By forming the thin portion 202 in the flexible portion F, the flexible portion F can be reduced without increasing the rigidity of the flexible portion F. The thin-walled portion 202 has a gradually decreasing section where the boundary with the thick-walled portion 201 is the section end and the thickness gradually decreases as the distance from the thick-walled portion 201 increases. Although the stress due to the deformation of the flexible portion F concentrates on the thin portion 202, it is distributed over the entire gradually decreasing section of the thin portion 202. As a result, the flexible part F is hard to break, and the impact resistance performance of the flexible part F is improved. Moreover, since it is not necessary to form the lower surface of the flexible part F in a curved surface, the manufacturing process can be simplified and the manufacturing cost can be reduced.

  The thick portion 201 and the thin portion 202 are formed on a straight line connecting one end coupled to the support portion S of the flexible portion F and the other end coupled to the weight portion M of the flexible portion F. Yes. That is, the thick part 201 and the thin part 202 are arranged in a direction away from the support part S in the flexible part F. The thin portion 201 extends over the entire width of the flexible portion F. That is, the thin part 201 crosses between two sides connecting the fixed end and the free end of the flexible part F. Such an arrangement of the thick part 201 and the thin part 202 makes the flexible part F easily bent. Therefore, the detection sensitivity of the piezoresistive element 40 and the piezoelectric element P can be increased.

  The weight portion M includes a thick silicon layer 101, an etching stopper layer 102, a thin silicon layer 104, and an insulating layer 106. Since the weight part M includes the thick silicon layer 101 and is coupled only to the flexible part F and floats from the bottom surface 90a of the package 1B, the weight part M behaves as a substantially rigid body that moves in a coordinate system fixed to the motion sensor 1.

  A total of twelve piezoresistive elements 40 are provided in the proximity region of the flexible portion F with the support portion S and the proximity region with the weight portion M. The piezoresistive element 40 includes a resistance portion 42 having a relatively low impurity concentration and a connection resistance reducing portion 41 having a high impurity concentration. All of these piezoresistive elements 40 straddle the boundary between the flexible portion F and the support portion S or the boundary between the flexible portion F and the weight portion M. The piezoresistive element 40 is formed on a thin silicon layer 104. The direction of the stress generated by the deformation of the flexible portion F is reversed between the upper surface and the lower surface of the flexible portion F. For this reason, the piezoresistive element 40 is formed thin near the interface of the thin silicon layer 104. The piezoresistive elements 40 form a bridge circuit with a set of four, and are wired so that output signals corresponding to three-axis acceleration components orthogonal to each other can be extracted from each bridge circuit.

  The resistance portion 42 of the piezoresistive element 40 is formed in the thin portion 202. When the flexible portion F bends, the thin portion 202 is more distorted than the thick portion 201. Therefore, by forming the resistance portion 42 in the thin portion 202, the detection sensitivity of the deflection of the flexible portion F due to acceleration. Can be increased. That is, by forming the resistance portion 42 in the thin portion 202, the detection sensitivity of acceleration accompanied by the bending of the flexible portion F is increased.

  The piezoelectric element P includes an electrode layer 108, a piezoelectric layer 110, and an electrode layer 112. The piezoelectric element P has a structure in which the piezoelectric layer 110 is sandwiched between the electrode layer 108 and the electrode layer 112. A part of the plurality of piezoelectric elements P functions as a driving unit that circulates the weight part M by distorting the flexible part F, and the remaining part detects the distortion of the flexible part F caused by the Coriolis force accompanying the angular velocity. It functions as a detection means.

  The piezoelectric element P is provided on the surface of the insulating layer 106 in the thin portion 202. When the flexible portion F bends, the thin portion 202 is more distorted than the thick portion 201. Therefore, by providing the piezoelectric portion P in the thin portion 202, the detection sensitivity of the deflection of the flexible portion F due to the angular velocity is increased. be able to. That is, by providing the piezoelectric element P in the thin portion, the detection sensitivity of the angular velocity accompanied by the bending of the flexible portion F is increased.

  A package 1 </ b> B shown in FIG. 2 includes a lidless box-type base 90 and a cover 94 that closes the internal space of the base 90. The base 90 and the cover 94 are joined via an adhesive layer 93. The base 90 is provided with a plurality of through electrodes 91. One end of the wire 95 is bonded to the surface wiring layer 50 of the die 1A, and the other end is bonded to the through electrode 91 of the package 1B. The support portion S of the die 1 </ b> A is bonded to the inner bottom surface 90 a of the base 90 with an adhesive layer 92. The height of the gap between the weight portion M of the die 1A and the bottom surface 90a inside the base 90 is set according to the depth of the recess formed in the bottom surface 90a and the thickness of the adhesive layer 92. Note that an LSI die connected to the die 1A may be accommodated in the package 1B.

(Production method)
Hereinafter, an example of a method for manufacturing the die 1A of the motion sensor 1 will be described with reference to FIGS. 3, 4A, 5 to 9, 11A, 12A, and 13 are cross-sectional views corresponding to the line BB shown in FIG. 1A. 10, FIG. 11B and FIG. 12B are cross-sectional views corresponding to the CC line shown in FIG. 1A.

First, as shown in FIG. 3, a laminated structure in which a thick silicon layer 101, an etching stopper layer 102, a thin silicon layer 104, a silicon oxide layer 105, and a silicon nitride layer 107 are laminated in this order is formed. Specifically, first, an SOI (Silicon On Insulator) wafer 100 including a thick silicon layer 101, an etching stopper layer 102, and a thin silicon layer 104 is prepared. Next, the surface of the thin silicon layer 104 is thermally oxidized to form a silicon oxide layer 105 made of silicon dioxide (SiO ₂ ). The thickness of the silicon oxide layer 105 at this stage is 30 nm. Next, a silicon nitride layer 107 made of silicon nitride (Si _x N _y ) is formed on the surface of the silicon oxide layer 105 by CVD or the like. The thickness of the silicon nitride layer 107 is 140 nm.

Next, as shown in FIG. 4A, the silicon nitride layer 107 is patterned into a predetermined shape by etching using a protective film R1 made of a photoresist. Specifically, patterning is performed by reactive ion etching using CHF ₃ gas as an etching gas. The protective film R1 has a slit RS for exposing the silicon oxide layer 105. FIG. 4B is a view of the protective film R1 as viewed from above, and a region corresponding to the flexible portion F is indicated by a broken line. A plurality of slits RS are arranged in a direction from one end to the other end of the flexible portion F in four regions where the flexible portions F are formed. Each slit RS crosses each of the four regions where the flexible portion F is formed. By forming the slit RS in this way, the thick portion 201 and the thin portion 202 are arranged on a straight line connecting one end and the other end of the flexible portion F, and the one end and the other end of the flexible portion F are connected to each other. A thin portion 202 that crosses between the sides can be formed. Next, as shown in FIG. 5, the protective film R1 is removed.

  Next, as shown in FIG. 6, a part of the thin silicon layer 104 is thermally oxidized using the silicon nitride layer 107 as a heat-resistant protective film. Specifically, the thin silicon layer 104 is heat-treated at 1050 ° C. By this treatment, the exposed region of the silicon oxide layer 105 grows and the thin silicon layer 104 shrinks. In the thermal oxidation, oxygen is diffused isotropically, so that the interface between the thin silicon layer 104 and the silicon oxide layer 105 is gently recessed downward immediately below the exposed region of the silicon oxide layer 105. The thin silicon layer 104 is thermally oxidized until the thickness of the thickest portion of the silicon oxide layer 105 becomes, for example, 1 μm.

  Next, as shown in FIG. 7, the silicon nitride layer 107 and the silicon oxide layer 105 are removed. At this time, since the region thermally oxidized in the previous process of the thin silicon layer 104 is removed as a part of the silicon oxide layer 105, a wave surface gently undulating is formed on the surface of the thin silicon layer 104 where the flexible portion F is formed. Is done. Specifically, the silicon nitride layer 107 and the silicon oxide layer 105 are removed by wet etching or the like using buffered hydrofluoric acid.

  Next, an insulating layer 106 is formed on the entire surface of the thin silicon layer 104 as shown in FIG. Specifically, the insulating layer 106 made of silicon oxide is formed by thermally oxidizing the entire surface of the thin silicon layer 104.

  Next, the laminated structure W shown in FIG. 9 in which a three-dimensional mechanical structure is not formed is formed by a known method such as laminating a thin film on the surface of the insulating layer 106, modifying it, or etching. For example, impurity ions are implanted from the surface of the thin silicon layer 104 through the insulating layer 106 and activated to form the piezoresistive element 40 in the thin silicon layer 104. The piezoresistive element 40 is formed in a section corresponding to the wavefront of the thin silicon layer 104 that becomes the flexible portion F. Next, an electrode layer 108 made of platinum is formed on the surface of the insulating layer 106, and the electrode layer 108 and the piezoresistive element 40 are connected through a contact hole. Next, a piezoelectric layer 110 made of PZT is formed on the entire surface of the electrode layer 108 by a sputtering method or a sol-gel method. Next, an electrode layer 112 made of platinum is formed on the entire surface of the piezoelectric layer 110. Then, the piezoelectric layer P is formed by etching the electrode layer 112, the piezoelectric layer 110, and the electrode layer 108 using a protective film made of a photoresist. The piezoelectric element P is formed in a section corresponding to the wavefront of the thin silicon layer 104 that becomes the flexible portion F. Next, a surface insulating layer 114 made of photosensitive polyimide is formed, and a contact hole and an opening for etching the flexible portion F are formed by exposure and development. Next, a surface wiring layer 115 made of aluminum connected to the electrode layers 108 and 112 exposed from the contact holes is formed. Next, when the surface wiring layer 115 is patterned by etching, a laminated structure W shown in FIG. 9 is obtained.

Next, as shown in FIG. 10, the insulating layer 106 and the thin silicon layer 104 are etched using the surface insulating layer 114 as a protective film to form a pattern of the flexible portion F and a part of the etching stopper layer 102 is exposed. Let Specifically, the insulating layer 106 made of silicon dioxide is etched by reactive ion etching using CHF ₃ gas. Subsequently, a thin silicon layer made of polycrystalline silicon is etched by reactive ion etching using CF ₄ gas.

  Next, as shown in FIGS. 11A and 11B, the laminated structure W is temporarily adhered to the sacrificial substrate 99, and a protective film R2 made of a photoresist is formed on the back surface of the thick silicon layer 101. The sacrificial substrate 99 and the laminated structure W can be temporarily bonded using the bonding means B made of wax, photoresist, double-sided pressure-sensitive adhesive sheet, or the like.

Next, as shown in FIGS. 12A and 12B, etching is performed until the thick silicon layer 101 exposed from the protective film R2 is penetrated to expose the etching stopper layer 102. Specifically, the thick silicon layer 101 is etched by Deep-RIE (Reactive Ion Etching), which is a Bosch process in which passivation using C ₄ F ₈ plasma and etching using SF ₆ plasma are alternately repeated at short intervals. . Thereafter, the protective film R2 is removed.

  Next, as shown in FIG. 13, the exposed region of the etching stopper layer 102 is etched using the thick silicon layer 101 as a mask. Specifically, the etching stopper layer 102 is removed from below the flexible portion F by wet etching using buffered hydrofluoric acid. Subsequently, when steps such as removal of the sacrificial substrate 99, dicing, and packaging are performed, the die 1A of the motion sensor is completed.

  According to the manufacturing method described above, since the wavefront undulation in the flexible portion F is gently formed, a MEMS sensor that is hard to break and excellent in impact resistance is manufactured.

2. Second Embodiment FIG. 14 shows a die 2A of a motion sensor according to a second embodiment of the present invention. In FIG. 14, the interface of the layers constituting the motion sensor die 2A is indicated by a broken line, and the boundary of the mechanical components constituting the motion sensor die 2A is indicated by a solid line. The motion sensor according to the second embodiment is different from the die 1A described in the first embodiment only in the cross-sectional structure of the die 2A, and other configurations are substantially the same as those of the motion sensor 1 described in the first embodiment.

The motion sensor die 2A includes a thick silicon layer 101, an etching stopper layer 102, a thin silicon layer 104, an epitaxial crystalline silicon layer 109, an insulating layer 106, electrode layers 108 and 112, a piezoelectric layer 110, a surface A laminated structure including an insulating layer 114 and a surface wiring layer 115. The thick silicon layer 101 having a thickness of 625 μm is made of p-type single crystal silicon (Si). The etching stopper layer 102 is made of a silicon oxide film (SiO ₂ ). The thickness of the etching stopper layer 102 is 1 μm. The thin silicon layer 104 having a thickness of 10 μm is made of n-type single crystal silicon. The thin silicon layer 104 is included in the support portion S and the weight portion M. The thin silicon layer 104 is not included in the flexible portion F. Epitaxial crystal silicon layer 109 is made of p-type single crystal silicon formed by epitaxial crystal growth of silicon. The thickness of the epitaxial crystalline silicon layer 109 is 10 μm. Epitaxial crystalline silicon layer 109 is included in support portion S, flexible portion F, and weight portion M. The reason why the thin silicon layer 104 is n-type and the epitaxial crystal layer 105 and the thick silicon layer 101 are p-type is to enable selective etching of the thin silicon layer 104. Therefore, the thin silicon layer 104 may be p-type, and the epitaxial crystal layer 105 and the thick silicon layer 101 may be n-type. The insulating layer 106 is made of a silicon oxide film. The thickness of the insulating layer 106 is 300 nm. The electrode layers 108 and 112 are both made of platinum (Pt). The electrode layers 108 and 112 both have a thickness of 0.1 μm. The piezoelectric layer 110 is made of PZT (lead zirconate titanate). The thickness of the piezoelectric layer 110 is 3 μm. The surface insulating layer 114 is made of photosensitive polyimide. The thickness of the surface insulating layer 114 is 10 μm. The surface wiring layer 115 is made of aluminum (Al). The thickness of the surface wiring layer 115 is 0.5 μm.

  Flexible portion F includes an epitaxial crystalline silicon layer 109 and an insulating layer 106. The flexible portion F has one end coupled to the support portion S and the other end coupled to the weight portion M. Since the flexible portion F does not include the thick silicon layer 101, the flexible portion F behaves as a flexible film. Each flexible part F has a corrugated section 203 that gently swells in a direction from a fixed end that is a boundary with the support part S to a free end that is a boundary with the weight part M. The corrugated section 203 extends over the entire width of the flexible portion F. That is, the waveform section 203 crosses between two sides connecting the fixed end and the free end of the flexible portion F. In the corrugated section 203, the upper surface and the lower surface of the flexible portion F are gently bent while keeping the mutual distance without bending.

  Since the corrugated section 203 is lower in rigidity than the flat section and easily bent, forming the corrugated section 203 in the flexible section F can reduce the flexible section F without increasing the rigidity of the entire flexible section F. . As a result, it is possible to reduce the size of the motion sensor without increasing the sensitivity of the motion sensor 1, expanding the dynamic range, or reducing the sensitivity. Further, since the undulation in the waveform section 203 is gentle, the stress concentration to the local area is alleviated as compared with the case where the rigidity of the flexible portion F is lowered by bending. As a result, the flexible part F becomes difficult to break, and the impact resistance performance of the motion sensor is improved. In addition, compared with the case where the flexible portion F is easily bent by forming a thin portion in the flexible portion F, the strength of the flexible portion F can be increased even if the corrugated section 203 is formed in the flexible portion F to bend easily. It wo n’t go down. Therefore, by forming the corrugated section 203 in the flexible portion F, the limit of the deformation amount of the flexible portion F can be set high and the rigidity can be set low. As a result, since the flexible portion F can be excited with a large amplitude efficiently by the piezoelectric element P, the detection sensitivity of the angular velocity can be increased. Moreover, since the limit of the deformation amount of the flexible portion F is high, a shift of the resonance frequency due to the hard spring effect can be prevented.

  The piezoresistive element 40 is formed in the epitaxial crystal silicon layer 109 in the waveform section 203 of the flexible portion F. When the flexible portion F is deformed along with the movement of the weight portion M, the waveform section 203 is more distorted than sections other than the waveform section 203 in the flexible portion F. For this reason, by forming the piezoresistive element 40 in the waveform section 203, it is possible to increase the detection sensitivity of acceleration and angular velocity accompanied by deformation of the flexible portion F.

15 to 19 are cross-sectional views showing a method of manufacturing the die 2A and correspond to the line BB shown in FIG. 1A.
First, as shown in FIG. 15, a protective film R <b> 3 made of a photoresist having a gently wavy surface is formed on the surface of the thin silicon layer 104 of the SOI wafer 100. The undulation on the surface of the protective film R3 corresponds to the undulation at the interface of the wave section 203 of the flexible portion F. Such a protective film R3 is formed as follows, for example. First, a positive photoresist having a thickness of 3 μm is applied to the surface of the thin silicon layer 104 and prebaked. Next, the photoresist may be exposed and developed through a multi-tone mask (halftone mask or graytone mask). By using a multi-tone mask, the protective film R3 having a three-dimensional pattern can be formed by one exposure and development. Note that an exposure region having a three-dimensional shape may be formed on the photoresist by a direct drawing method using laser light.

Next, the surface shape of the protective film R3 is transferred to the thin silicon layer 104 by anisotropically etching the thin silicon layer 104 together with the protective film R3. As a result, a wavefront region 104a corresponding to the wavefront of the flexible portion F is formed on the surface of the thin silicon layer 104 as shown in FIG. For example, the surface shape of the protective film R3 is transferred to the thin silicon layer 104 by reactive ion etching using CF ₄ —O ₂ as an etching gas. At this time, by setting the selection ratio of the thin silicon layer 104 and the protective film R3 to 1: 1, the wavefront of the protective film R3 can be transferred to the thin silicon layer 104 as it is. When the selection ratio is not 1: 1, a wavefront having an amplitude different from that of the protective film R3 is formed in the thin silicon layer 104.

Next, an epitaxial crystal silicon layer 109 is epitaxially grown on the surface of the thin silicon layer 104 as shown in FIG. As a result, an epitaxial crystalline silicon layer 109 having a portion that becomes the waveform section 203 of the flexible portion F is formed. The P-type epitaxial crystal silicon layer 109 can be grown by causing a reaction of SiH ₂ Cl ₂ → Si + 2HCl by supplying SiH ₂ Cl ₂ gas at a reaction temperature of 1050 ° C. to 1150 ° C.

  Thereafter, as in the first embodiment, the insulating layer 106, the electrode layers 108 and 112, the piezoelectric layer 110, the surface insulating layer 114, and the surface wiring layer 115 are formed, and these are modified or patterned. At this time, the piezoresistive element 40 and the piezoelectric element P are formed in the waveform section 203 of the epitaxial crystal layer 105 to be the flexible portion F.

  Further, as in the first embodiment, the thick silicon layer 101 and the etching stopper layer 102 are etched as shown in FIG.

  Next, the thin silicon layer 104 is etched as shown in FIG. 19 using the thick silicon layer 101 and the etching stopper layer 102 as protective films. As a result, thin silicon layer 104 is removed from the surface of the portion corresponding to flexible portion F of epitaxial crystalline silicon layer 109. The n-type thin silicon layer 104 is selectively etched by electrochemical etching. At this time, the p-type thick silicon layer 101 is not etched, and the p-type epitaxial crystal silicon layer 109 serves as an etching stopper.

  After that, when steps such as removal of the sacrificial substrate 99, dicing, and packaging are performed, the motion sensor die 2A is completed.

3. 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 thin portion 202 and a thick portion 201 may be formed in a diaphragm-type flexible portion F as shown in FIG. When the flexible portion F is an annular diaphragm type, the thin portion 202 is preferably formed so as to go around the flexible portion F once. Further, as shown in FIG. 20B, the entire thin portion 202 may be a gradually decreasing section. FIG. 20A is a top view showing a diaphragm-type flexible portion F. FIG. In FIG. 20A, the area of the thin portion 202 is hatched. 20B is a cross-sectional view corresponding to the line BB shown in FIG. 20A. Further, for example, a corrugated section may be formed in the diaphragm-type flexible portion F. When the corrugated section is formed in the diaphragm-type flexible portion F, it is preferable that the area shown by hatching in FIG. In addition, for example, as shown in FIG. 21, the thickness of the flexible portion F may decrease linearly as the distance from the thick portion 201 increases in the gradually decreasing section 202 a of the thin portion 202. FIG. 21A is a top view showing a beam-shaped flexible portion F. FIG. In FIG. 21A, the area of the thin portion 202 is hatched. FIG. 21B is a cross-sectional view corresponding to the line BB shown in FIG. 21A.

  Further, the present invention is naturally applicable to other MEMS sensors such as an acceleration sensor, an angular velocity sensor, an attitude sensor, a vibration sensor, a microphone, and a pressure sensor. In addition, the materials, dimensions, film forming methods, and pattern transfer methods shown in the above embodiment are merely examples, and descriptions of addition and deletion of processes and replacement of the process order that are obvious to those skilled in the art are omitted. Yes. For example, in the above-described manufacturing process, the film composition, film forming method, film contour forming method, process sequence, etc. are combinations of film materials having physical properties that can constitute a condenser microphone, film thickness, and required contour. It is appropriately selected according to the shape accuracy and the like and is not particularly limited.

FIG. 1A is a plan view according to the first embodiment of the present invention. 1B is a cross-sectional view taken along line BB shown in FIG. 1A. 1C is a cross-sectional view taken along line CC shown in FIG. 1A. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. FIG. 4A is a sectional view according to the first embodiment of the present invention. FIG. 4B is a plan view according to the 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. FIG. 11A is a sectional view according to the first embodiment of the present invention. FIG. 11B is a cross-sectional view according to the first embodiment of the present invention. FIG. 12A is a sectional view according to the first embodiment of the present invention. FIG. 12B is a cross-sectional view according to the first embodiment of the present invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 2nd embodiment of this invention. Sectional drawing concerning 2nd embodiment of this invention. Sectional drawing concerning 2nd embodiment of this invention. Sectional drawing concerning 2nd embodiment of this invention. Sectional drawing concerning 2nd embodiment of this invention. Sectional drawing concerning 2nd embodiment of this invention. FIG. 20A is a plan view according to another embodiment of the present invention. FIG. 20B is a cross-sectional view according to another embodiment of the present invention. FIG. 21A is a plan view according to another embodiment of the present invention. FIG. 21B is a sectional view according to another embodiment of the present invention.

Explanation of symbols

1: Motion sensor, 1A: Die, 1B: Package, 2A: Die, 40: Piezoresistive element, 41: Connection resistance reduction part, 42: Resistance part, 50: Surface wiring layer, 90: Base, 90a: Bottom, 91 : Through electrode, 92: adhesive layer, 93: adhesive layer, 94: cover, 95: wire, 99: sacrificial substrate, 100: wafer, 101: thick silicon layer, 102: etching stopper layer, 104: thin silicon layer, 104a : Wavefront region, 105: silicon oxide layer, 109: epitaxial crystal silicon layer, 106: insulating layer, 107: silicon nitride layer, 108: electrode layer, 110: piezoelectric layer, 112: electrode layer, 114: surface insulating layer, 115 : Surface wiring layer, 115: surface insulating layer, 201: thick part, 202: thin part, 203: corrugated section, B: adhesive means, F: flexible part, M: weight part, : Piezoelectric elements, R1: protective film, R2: protective film, R3: protective film, RS: slit, S: supporting unit, W: laminated structure

Claims (14)

A support part;
One end is a flexible membrane bonded to the support part, and the boundary between the thick part and the thick part is a section end, and the thickness gradually decreases as the distance from the thick part increases. A flexible portion in which a thin portion having a section is arranged in a direction away from the one end;
A strain detecting means for detecting a strain formed in the thin portion and formed in the thin portion;
A MEMS sensor comprising: A weight portion coupled to the other end of the flexible portion;
The thick part and the thin part are formed on a straight line connecting one end and the other end of the flexible part,
The MEMS sensor according to claim 1. The flexible portion is a beam having one end coupled to the support portion and the other end coupled to the weight portion,
The thin portion crosses between two sides connecting one end and the other end of the beam,
The MEMS sensor according to claim 2. The flexible portion is an annular diaphragm having one end coupled to the support portion and the other end coupled to the weight portion,
The thin-walled portion goes around the diaphragm,
The MEMS sensor according to claim 2. One of the main surfaces of the flexible portion is flat and the other of the main surfaces of the flexible portion is gently recessed in the thin portion,
The MEMS sensor as described in any one of Claim 1 to 4. A support part;
A flexible part having one end connected to the support part and having a corrugated section gently undulating in a direction away from the one end;
Distortion detecting means for detecting distortion generated in the waveform section formed in the waveform section;
A MEMS sensor comprising: A weight portion coupled to the other end of the flexible portion;
The corrugated section gently undulates in the direction from one end of the flexible portion to the other end,
The MEMS sensor according to claim 6. The flexible portion is a beam having one end coupled to the support portion and the other end coupled to the weight portion,
The corrugated section crosses between two sides connecting one end and the other end of the beam,
The MEMS sensor according to claim 7. The flexible portion is an annular diaphragm having one end coupled to the support portion and the other end coupled to the weight portion,
The waveform section goes around the diaphragm,
The MEMS sensor according to claim 7. Forming a gently wave front on the surface of the second silicon layer of an SOI wafer including a first silicon layer and a second silicon layer thinner than the first silicon layer;
A support part including the first silicon layer, and a flexible film having one end coupled to the support part and including the second silicon layer and not including the first silicon layer, in a direction away from the support part; Forming a gently wavy flexible part having the wavefront by removing a portion of the first silicon layer;
Forming strain detection means for detecting strain of the flexible part in a section corresponding to the wavefront of the flexible part;
A method for manufacturing a MEMS sensor. Forming a heat-resistant protective film having a predetermined pattern on the second silicon layer;
Thermally oxidizing the second silicon layer located under the heat-resistant protective film;
Forming the wavefront by selectively removing thermally oxidized regions of the second silicon layer;
The manufacturing method of the MEMS sensor of Claim 10. Forming a protective film having a predetermined three-dimensional pattern on the surface of the second silicon layer;
The wavefront is formed by anisotropically etching the second silicon layer together with the protective film.
The manufacturing method of the MEMS sensor of Claim 10. Forming the protective film by exposure and development through a multi-tone mask;
A method for manufacturing the MEMS sensor according to claim 12. Forming a wavefront region that gently undulates on the surface of the second silicon layer in an SOI wafer including a first silicon layer and a second silicon layer that is thinner than the first silicon layer;
Epitaxially growing an epitaxial crystal silicon layer on the surface of the second silicon layer in which the wavefront region is formed;
A supporting portion including the first silicon layer, and a flexible film having one end coupled to the supporting portion and including the epitaxial crystalline silicon layer and not including the first silicon layer, in a direction away from the supporting portion. Forming a flexible portion including a wavy section corresponding to the wavefront region by selectively removing a part of the first silicon layer and a part of the second silicon layer;
Forming a strain detection means in the waveform section for detecting the strain of the flexible portion;
A method for manufacturing a MEMS sensor.

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