JP2006064532A - Semiconductor acceleration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shock-resistant semiconductor acceleration sensor which reduces a breakage of a stopper piece which limits the amount of displacement of a weight part in a direction perpendicular to one surface of a flame part. <P>SOLUTION: In a sensor chip 1, the weight part 12 placed in a window of the rectangular flame part 11 is oscillatably supported by the flame part 11 through a deformation part 13 on the one surface of the flame part 11. The weight part 12 includes a core part 12a and an attached part 12b which is integral with the core part 12a and is placed in the space between the core part 12a and the flame part 11. The flame part 11 departs from the attached part 12b in a direction perpendicular to the one surface. The thin-walled stopper piece 15 for limiting the amount of displacement of the attached part 12b toward the one surface is integrally protruded from each corner part 11a. A reinforcement part 16 for reinforcing the stopper piece 15 on a surface facing the attached part 12b on the stopper piece 15 is integrally protruded. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor acceleration sensor, and more particularly to a semiconductor acceleration sensor excellent in impact resistance.

  As this type of semiconductor acceleration sensor, for example, as shown in FIGS. 10A and 10B, a sensor chip 1 ′ formed using a silicon substrate and a glass chip fixed to the back side of the sensor chip 1 ′ are used. A pedestal 2 'is proposed.

  The sensor chip 1 ′ includes a rectangular frame-shaped frame portion 11 ′, and a weight portion 12 ′ disposed in a rectangular opening window of the frame portion 11 ′ is on one surface side of the frame portion 11 ′ (sensor chip 1 ′ Is supported by the frame portion 11 ′ in a swingable manner through four thin flexible portions 13 ′ having flexibility. In the pedestal 2 ′, a recess 2 a ′ is formed on the surface of the pedestal 2 ′ facing the weight portion 12 ′ so that the weight portion 12 ′ can be displaced in the thickness direction of the weight portion 12 ′.

  The weight portion 12 ′ is formed integrally with the core portion 12a ′ supported by the frame portion 11 ′ via the above-described four bent portions 13 ′ and the core portion 12a ′, and the back surface side of each bent portion 13 ′. In FIG. 4, the auxiliary portion 12b ′ is disposed in the space between the frame portion 11 ′ and the core portion 12a ′, and a slit 14 ′ is formed between the frame portion 11 ′ and the auxiliary portion 12b ′. ing.

  As shown on the left side of each of FIGS. 10A and 10B, the sensor chip 1 ′ described above has a rectangular frame shape on the plane orthogonal to the z-axis direction and the z-axis direction in the thickness direction of the sensor chip 1 ′. If the direction along one side of the frame portion 11 ′ is defined as the x-axis direction, and the direction along the side perpendicular to the one side is defined as the y-axis direction, the sensor chip 1 ′ has two longitudinal directions in the x-axis direction. Two piezoresistors (not shown) for detecting acceleration in the x-axis direction are formed in the vicinity of the core portion 12a ′ in the bent portions 13 ′ and 13 ′, and the two bent portions have a longitudinal direction in the y-axis direction. Two piezoresistors (not shown) for detecting acceleration in the y-axis direction are formed in the vicinity of the core portion 12a ′ in 13 ′ and 13 ′, and the frame portion 11 in the longitudinal direction of each of the four bent portions 13 ′. 'Detect the acceleration in the z-axis direction in the vicinity One piezoresistor (not shown) is formed, and four piezoresistors are connected by wiring (not shown) such as diffusion layer wiring so that each piezoresistor forms a bridge circuit for each axial direction. A pad (not shown) connected to each bridge circuit is formed on the one surface side of the frame portion 11 '.

  Therefore, when an acceleration acts on the sensor chip 1 ′, the weight portion 12 ′ is displaced relative to the frame portion 11 ′ according to the direction and magnitude of the acceleration, and as a result, the bending portion 13 ′ is bent and the piezoelectric element is bent. The resistance value of the resistor will change. That is, by detecting a change in the resistance value of the piezoresistor, it is possible to detect accelerations in the x-axis direction, the y-axis direction, and the z-axis direction that act on the sensor chip 1 '.

  By the way, the sensor chip 1 ′ is separated from the associated portion 12b ′ in the direction orthogonal to the one surface of the frame portion 11 ′ (that is, the z-axis direction) and restricts the amount of displacement of the associated portion 12b ′ toward the one surface side. A thin stopper piece 15 ′ is integrally projected from each of the four corner portions of the frame portion 11 ′. Here, each stopper piece 15 'has a triangular shape in a plane parallel to the one surface.

Thus, in the semiconductor acceleration sensor shown in FIG. 10, the amount of displacement of the weight portion 12 ′ in the z-axis direction is limited by the stopper piece 15 ′ and the base 2 ′ (the weight in the upward direction in FIG. 10B). The displacement amount of the portion 12 ′ is limited by the stopper piece 15 ′, and the displacement amount of the weight portion 12 ′ in the downward direction in FIG. 10B is limited by the pedestal 2 ′). It is possible to suppress the bending portion 13 ′ from being damaged when the is applied.
JP-A-8-327656

  However, in the semiconductor acceleration sensor having the configuration shown in FIG. 10, the impact when the associated portion 12b ′ of the weight portion 12 ′ collides with the stopper piece 15 ′ is locally concentrated and the stopper piece 15 ′ is destroyed. Since there is a fear, realization of a semiconductor acceleration sensor having further improved shock resistance is expected.

  The present invention has been made in view of the above-mentioned reasons, and the purpose thereof is to prevent the stopper piece from limiting the amount of displacement of the weight portion in the direction perpendicular to one surface of the frame portion, and to be excellent in impact resistance. Another object of the present invention is to provide a semiconductor acceleration sensor.

  In order to achieve the above object, the invention according to claim 1 is a thin flexible portion in which the weight portion disposed in the rectangular opening window of the frame-like frame portion is flexible on one surface side of the frame portion. The semiconductor acceleration sensor is supported by the frame part through the frame, and the weight part is a core in which one end part is connected to the inner side surface of the frame part and the other end part of the bending part is connected to the outer side surface. And an associated part formed integrally with the core part and disposed in a space between the core part and the frame part. The frame part is spaced apart from the associated part in a direction perpendicular to the one surface, and A thin stopper piece that limits the amount of displacement of the accompanying part to the surface side is projected integrally from the corner part, and a reinforcing part that reinforces the stopper piece is integrally projected on the side of the stopper piece facing the accompanying part. It is characterized by.

  According to the present invention, since the reinforcing portion that reinforces the stopper piece is integrally provided on the frame portion, the stopper piece is reinforced by the reinforcing portion, and the accompanying portion of the weight portion collides with the stopper piece. It is possible to prevent the stopper piece from being damaged by the impact at the time, and the impact resistance can be improved as compared with the conventional case.

  According to a second aspect of the present invention, in the first aspect of the invention, the reinforcing portion is formed along a direction in which the stopper piece and the associated portion face each other on the side of the stopper piece facing the associated portion. It is characterized by being made.

  According to the present invention, the stopper piece can be effectively reinforced while the area of the portion overlapping the reinforcing portion in the stopper piece is relatively small, and the area of the portion overlapping the accompanying portion in the stopper piece. It is possible to prevent the stopper piece from being damaged while relatively large.

  The invention of claim 3 is characterized in that, in the invention of claim 1 or 2, a chamfered portion is formed between the inner side surface of the frame portion and the side surface of the reinforcing portion.

  According to the present invention, when the accompanying portion of the weight portion collides with the stopper piece, it is possible to suppress stress concentration on the connecting portion between the inner side surface of the frame portion and the side surface of the reinforcing portion, thereby stress concentration. The breakage of the reinforcing part due to the above can be suppressed, and the impact resistance is improved as compared with the case where the chamfered part is not formed.

  According to a fourth aspect of the present invention, in the first to third aspects of the invention, the reinforcing portion has a shape in which a cross-sectional area gradually increases as it approaches the stopper piece in a direction perpendicular to the one surface of the frame portion. It is formed.

  According to the present invention, when the accompanying portion of the weight portion collides with the stopper piece, it is possible to suppress stress concentration on the connection portion of the stopper piece with the reinforcing portion, and the stopper piece is caused by stress concentration. Damage can be suppressed.

  According to a fifth aspect of the present invention, in the first to fourth aspects of the present invention, the weight portion is a concave portion into which the reinforcing portion is inserted into an outer peripheral surface of the associated portion, and is predetermined between a side surface of the reinforcing portion. Concave portions that form gaps are provided, and the predetermined interval is set to be smaller than the interval between the associated portion and the frame portion.

  According to this invention, the displacement amount of the weight portion in a plane orthogonal to the one surface of the frame portion is limited by the reinforcing portion, and in addition to the function of the reinforcing portion reinforcing the stopper piece. In addition, it has a function as a stopper for limiting the amount of displacement of the weight portion in a plane orthogonal to the one surface of the frame portion, and the impact resistance is further improved.

  According to a sixth aspect of the present invention, in the first to fourth aspects of the present invention, a convex portion provided integrally with at least one of the accompanying portion and the reinforcing portion is inserted, and a gap having a predetermined interval is formed between the convex portion. A concave portion to be formed is provided on the other side, and the predetermined interval is set to be smaller than an interval between the accompanying portion and the frame portion.

  According to this invention, the displacement amount of the weight portion in a plane orthogonal to the one surface of the frame portion is limited by the reinforcing portion, and in addition to the function of the reinforcing portion reinforcing the stopper piece. In addition, it has a function as a stopper for limiting the amount of displacement of the weight portion in a plane orthogonal to the one surface of the frame portion, and the impact resistance is further improved.

  In invention of Claim 1, it can suppress that a stopper piece is damaged by the impact at the time of the incidental part of a weight part colliding with a stopper piece, and there exists an effect that impact resistance can be improved compared with the past. is there.

(Embodiment 1)
The semiconductor acceleration sensor of the present embodiment is composed of a sensor chip 1 shown in FIGS. 1A to 1E. For example, the semiconductor acceleration sensor is directly on a base member such as a package or a circuit board (for example, a printed board) or made of glass. It may be mounted in the form through the pedestal. Here, as shown in FIG. 2A, the sensor chip 1 includes an n-type silicon layer (an active layer) on an insulating layer (buried oxide film) 22 made of a silicon oxide film on a support substrate 21 made of a silicon substrate. The SOI wafer 20 having the (layer) 23 is formed by processing.

  The sensor chip 1 includes a frame portion 11 having a frame shape (in this embodiment, a rectangular frame shape), and a weight portion 12 disposed in a rectangular opening window of the frame portion 11 has one surface of the frame portion 11 (see FIG. 1 (b) is supported swingably on the frame portion 11 via four strip-like flexure portions 13 having flexibility. Therefore, if the mass of the weight portion 12 is m, the acceleration acting on the sensor chip 1 is α, and the force acting on the weight portion 12 is F, the force of F = mα derived from the Newton's equation of motion on the weight portion 12. Acts to bend the bent portion 13. The frame portion 11 is formed using the support substrate 21, the insulating layer 22, and the silicon layer 23 of the SOI wafer 20. On the other hand, the bending portion 13 is formed using the silicon layer 23 in the SOI wafer 20 and is thinner than the frame portion 11.

  The weight part 12 is seen from the rectangular parallelepiped core part 12a supported by the frame part 11 via the above-described four flexure parts 13 and the main surface side of the sensor chip 1 (the one surface side of the frame part 11). It has four rectangular parallelepiped portions 12b continuously and integrally connected to the four corners of the core portion 12a. In other words, the weight portion 12 is formed integrally with the core portion 12a and the core portion 12a in which the other end portion of each bending portion 13 whose one end portion is connected to the inner side surface of the frame portion 11 is connected to the outer surface. It has four accompanying parts 12b arranged in the space between the part 12a and the frame part 11. That is, each of the accompanying portions 12b is viewed from the main surface side of the sensor chip 1 (the one surface side of the frame portion 11), and the two bent portions 13 extended in a direction orthogonal to the frame portion 11 and the core portion 12a. , 13, a slit 14 is formed between each of the associated portions 12 b and the frame portion 11, and the interval between the adjacent associated portions 12 b across the bent portion 13 is defined as a bent portion. It is longer than 13 width dimensions. Here, the core portion 12 a is formed using the support substrate 21 of the SOI wafer 20, the insulating layer 22, and the silicon layer 23, and each accompanying portion 12 b is formed using the support substrate 21 of the SOI wafer 20. It is. Thus, on the one surface side of the frame portion 11, the surface of each associated portion 12b (upper surface in FIG. 1B) is formed from the plane including the surface of the core portion 12a (upper surface in FIG. 1B). It is located away from the other surface (the lower surface in FIG. 1B).

  In addition, the core portion 12 a and the associated portions 12 b of the weight portion 12 are formed so that the thickness of the portion formed using the support substrate 21 is the thickness of the portion formed using the support substrate 21 in the frame portion 11. Compared to this, the sensor chip 1 is thinner by the allowable displacement amount of the weight portion 12 in the thickness direction (vertical direction in FIG. 1B). Therefore, when the other surface of the frame portion 11 of the sensor chip 1 is fixed to the base member or the pedestal, the thickness direction of the sensor chip 1 is on the back surface (the lower surface in FIG. 1B) of the weight portion 12. For example, in the case of being fixed to the pedestal, it is necessary to provide a recess for enabling the displacement of the weight portion 12 in the pedestal. The manufacturing cost can be reduced.

  By the way, as shown on the left side of each of FIGS. 1A and 1B, the thickness direction of the sensor chip 1 is along the z-axis direction and along one side of the frame portion 11 having a rectangular frame shape in a plane orthogonal to the z-axis direction. When the direction along the side perpendicular to the one side is defined as the y-axis direction, the weight portion 12 extends in the x-axis direction and sandwiches the core portion 12a. 13 and 13 and the pair of flexible portions 13 and 13 that extend in the y-axis direction and sandwich the core portion 12a, are supported by the frame portion 11. Here, the sensor chip 1 has two piezoresistors (not shown) for detecting acceleration in the x-axis direction in the vicinity of the core portion 12a in the two flexures 13 and 13 whose longitudinal direction is the x-axis direction. Two piezoresistors (not shown) for detecting acceleration in the y-axis direction are formed in the vicinity of the core portion 12a in the two bent portions 13 and 13 having the longitudinal direction in the y-axis direction. One piezoresistor (not shown) for detecting acceleration in the z-axis direction is formed in the vicinity of the frame portion 11 in the longitudinal direction of each of the bent portions 13, and four piezoresistors are provided for each axial direction. They are connected via wiring (diffusion layer wiring, metal wiring, etc.) so as to form a bridge circuit. Here, a protective film (not shown) made of a silicon oxide film is formed on the one surface side of the sensor chip 1, and pads (not shown) serving as terminals of the bridge circuit are formed on the frame portion 11. The corresponding part is provided on the one surface side of the sensor chip 1. The pad is made of a metal material (for example, aluminum).

  Therefore, when acceleration is applied to the sensor chip 1, the weight portion 12 is displaced relative to the frame portion 11 according to the direction and magnitude of the acceleration, and as a result, the bending portion 13 is bent and the resistance value of the piezoresistor is increased. Will change. That is, by detecting a change in the resistance value of the piezoresistor, accelerations in the x-axis direction, the y-axis direction, and the z-axis direction that act on the sensor chip 1 can be detected. In short, if an appropriate power source for detection is connected between one terminal at the diagonal position of each bridge circuit, a voltage between the other terminal at the diagonal position is detected, and appropriate correction is applied, the weight 12 is affected. A voltage proportional to the acceleration in each of the x-axis direction, the y-axis direction, and the z-axis direction can be obtained. In the present embodiment, each piezoresistor constitutes a resistor whose resistivity changes due to strain generated in the bending portion 13 due to the displacement of the weight portion 12 with respect to the frame portion 11.

  In this embodiment, since the conductivity type of the silicon layer 23 is n-type, the conductivity type of each piezoresistor and each diffusion layer wiring is p-type. However, when the conductivity type of the silicon layer 23 is p-type. In this case, the conductivity type of each piezoresistor and each diffusion layer wiring may be n-type. For the SOI wafer 20, the thickness of the support substrate 21 is set to about 400 to 600 μm, the thickness of the insulating layer 22 is set to about 0.3 to 1.5 μm, and the thickness of the silicon layer 23 is set to about 4 to 6 μm. However, these numerical values are not particularly limited. The surface of the silicon layer 23 which is the main surface of the SOI wafer 20 is a (100) plane.

  By the way, the sensor chip 1 is separated from each of the accompanying portions 12b in a direction orthogonal to the one surface of the frame portion 11 (that is, the z-axis direction) and restricts the amount of displacement of each accompanying portion 12b toward the one surface side. Four thin stopper pieces 15 are integrally projected from the four corner portions 11 a of the frame portion 11. Here, the planar shape of each stopper piece 15 is a triangular shape, but the planar shape of the stopper piece 15 is not limited to a triangular shape, for example, a rectangular shape, It may be a fan shape. Each stopper piece 15 is formed using the silicon layer 23 in the SOI wafer 20 in the same manner as the bent portion 13.

  In the sensor chip 1, a reinforcing portion (reinforcing rib) 16 that reinforces the stopper piece 15 is integrally projected from each corner portion 11 a of the frame portion 11 on the side of the stopper piece 15 facing the associated portion 12 b. Yes. The reinforcing part 16 is constituted by a part of the insulating layer 22 of the SOI wafer 20 and a part of the support substrate 21, and the dimension of the reinforcing part 16 in the z-axis direction described above is the thickness of the support substrate 21 and the insulating layer. The thickness is set to be slightly smaller than the total thickness of 22 and specifically, the thickness is set to the sum of the thickness of the associated portion 12b and the thickness of the insulating layer 22 in the z-axis direction. In short, each reinforcing portion 16 is formed along the direction orthogonal to the one surface of the frame portion 11 on the side of the stopper piece 15 facing the associated portion 12b. In other words, each reinforcing portion 16 is formed along the direction in which the stopper piece 15 and the associated portion 12b face each other on the surface of each stopper piece 15 facing the associated portion 12b. However, the direction in which the stopper piece 15 and the accompanying portion 12b face each other does not mean only the direction orthogonal to the one surface of the frame portion 11, but the direction substantially orthogonal to the one surface of the frame portion 11. I mean. Here, in the sensor chip 1, the portion configured by the stopper piece 15 and the reinforcing portion 16 that reinforces the stopper piece 15 has a T-shaped cross section perpendicular to the protruding direction of the reinforcing portion 16. (See FIG. 1 (d)). Therefore, in the sensor chip 1, the associated portion 12 b can come into contact with a portion of the stopper piece 16 that does not overlap with the reinforcing portion 16 in the z-axis direction.

  In the sensor chip 1, a chamfered portion 17 is formed between the inner side surface of the frame portion 11 and the side surface of the reinforcing portion 16. Here, the chamfered portion 17 is formed in a curved shape that is smoothly continuous with the inner side surface of the frame portion 11 and the side surface of the reinforcing portion 16. Further, the sensor chip 1 is a concave portion into which the reinforcing portion 16 enters the outer peripheral surface of the associated portion 12b in the weight portion 12, and a gap of a predetermined distance d1 (see FIG. 1 (e)) between the side surface of the reinforcing portion 16. A concave portion 12c is formed. Here, the predetermined interval d1 is set to be smaller than the interval between the associated portion 12b of the weight portion 12 and the frame portion 11. That is, the predetermined interval d1 is set to be smaller than the width d2 (see FIG. 1E) of the slit 14 formed between the associated portion 12b of the weight portion 12 and the frame portion 11.

  Hereinafter, a method for manufacturing the sensor chip 1 shown in FIG. 1 will be described with reference to FIG. 2. FIG. 2 shows a cross section of a portion corresponding to the BB ′ cross section of FIG. .

  First, a silicon oxide film (not shown) is formed by a pyrogenic oxidation method on the main surface side and the back surface side of the SOI wafer 20, and then corresponds to the rectangular opening window of the frame portion 11 on the back surface side of the SOI wafer 20. In order to form a mask when forming a recess 20a (see FIG. 2A) having the above-mentioned allowable displacement amount at a predetermined depth in a portion to be subjected to, an SOI wafer 20 using photolithography technology and etching technology. The oxide film on the back side is patterned. Subsequently, the recess 20a is formed by etching the SOI wafer 20 from the back surface side to a predetermined depth using the patterned silicon oxide film on the back surface side of the SOI wafer 20 as a mask, thereby forming the structure shown in FIG. Get. In the etching step for forming the recess 20a, wet etching using an alkaline solution such as KOH (potassium hydroxide aqueous solution) or TMAH (tetramethylammonium aqueous solution) may be performed, or RIE ( Dry etching such as reactive ion etching may be performed.

  Thereafter, in order to form a mask for forming the above-described diffusion layer wiring, the silicon oxide film on the main surface side of the SOI wafer 20 is patterned using a photolithography technique and an etching technique. Subsequently, p-type impurities (for example, boron) are introduced into the silicon layer 23 by ion implantation or predeposition using the patterned silicon oxide film on the main surface side of the SOI wafer 20 as a mask. Thereafter, simultaneously with the formation of the diffusion layer wiring by the diffusion of the p-type impurity, a silicon oxide film (not shown) is formed on the exposed silicon layer 23 surface. The silicon oxide film formed at the time of diffusion and the above-described silicon oxide film first formed on the main surface side of the SOI wafer 20 constitute an insulating film made of a silicon oxide film. As the process conditions in this diffusion step, for example, the processing temperature (diffusion temperature) is set to 1100 ° C., the processing time (diffusion time) is set to 30 minutes, and the atmosphere in the processing furnace (diffusion furnace) is steam. As a mixed gas with oxygen.

  Next, in order to form a mask for forming each of the piezoresistors described above, the insulating film on the main surface side of the SOI wafer 20 is patterned using a photolithography technique and an etching technique. Subsequently, p-type impurities (for example, boron) are introduced into the silicon layer 23 by ion implantation or predeposition using the patterned insulating film on the main surface side of the SOI wafer 20 as a mask. Thereafter, simultaneously with the formation of each piezoresistor by diffusion of p-type impurities, a silicon oxide film is formed on the exposed silicon layer 23 surface. The silicon oxide film formed at the time of diffusion and the insulating film constitute a protective film made of a silicon oxide film. As the process conditions in this diffusion step, for example, the processing temperature (diffusion temperature) is set to 1100 ° C., the processing time (diffusion time) is set to 30 minutes, and the atmosphere in the processing furnace (diffusion furnace) is steam. As a mixed gas with oxygen.

  Subsequently, a contact hole (not shown) for electrically connecting the diffusion layer wiring and the pad is formed in the protective film by using the photolithography technique and the etching technique, and the main surface side of the SOI wafer 20 is formed. A metal film is formed by sputtering or the like, and the metal film is patterned by using a photolithography technique and an etching technique to form a pad.

  Thereafter, on the back surface side of the SOI wafer 20, a portion 211 (see FIG. 2B) corresponding to the frame portion 11 and a portion 212 (see FIG. 2B) corresponding to the core portion 12 a on the support substrate 21. A resist layer (see FIG. 2) patterned so as to cover a portion 213 (see FIG. 2B) corresponding to each of the portions 12b and a portion (not shown) corresponding to each of the reinforcing portions 16 and to expose the other portions. (Not shown), and using the resist layer as an etching mask, a back side patterning process is performed in which the SOI wafer 20 is dry-etched substantially perpendicularly from the back side to a depth reaching the insulating layer 22, and then the resist layer is removed. As a result, the structure shown in FIG. By performing this back surface side patterning step, the support substrate 21 in the SOI wafer 20 includes a part 211 corresponding to the frame part 11, a part 212 corresponding to the core part 12a, and a part 213 corresponding to each of the accompanying parts 12b. The portions corresponding to the respective reinforcing portions 16 remain. For example, an inductively coupled plasma (ICP) type dry etching apparatus may be used as an etching apparatus in the back surface side patterning step, and the etching conditions are set such that the insulating layer 22 functions as an etching stopper. To do.

  After the back side patterning step, the main surface side of the SOI wafer 20 covers the portions corresponding to the frame portion 11, the core portion 12 a, the bending portions 13, and the stopper pieces 15 in the protective film, and exposes other portions. A resist layer (not shown) patterned so as to be etched, the protective film is etched using the resist layer as an etching mask, and then the SOI wafer 20 is etched from the main surface side to a depth reaching the insulating layer 22 By performing the side patterning step, the structure shown in FIG. By performing this surface side patterning step, the silicon layer 23 in the SOI wafer 20 has a portion 231 corresponding to the frame portion 11, a portion 232 corresponding to the core portion 12 a, and a portion 233 corresponding to each of the bent portions 13. The portions 234 corresponding to the respective stopper pieces 15 remain. In the etching in the surface side patterning process, for example, dry etching may be performed using an inductively coupled plasma (ICP) type dry etching apparatus. Instead of dry etching, for example, an etching rate crystal is used as an etching solution. Wet etching may be performed using TMAH, which enables anisotropic etching of the silicon layer 23 using orientation dependency and has a high etching selectivity with the insulating layer 22. Etching conditions are set such that the insulating layer 22 functions as an etching stopper in both dry etching and wet etching.

  After the surface-side patterning step, a portion of the insulating layer 22 corresponding to the frame portion 11 is sprayed from the main surface side of the SOI wafer 20 in the form of a mist using the resist layer as an etching mask. 221 (see FIG. 2 (d)), a portion 222 (see FIG. 2 (d)) corresponding to the core portion 12a and a portion (not shown) corresponding to each of the reinforcing portions 16 are removed by etching. As a result, the frame portion 11, the bending portions 13, the weight portion 12, the stopper pieces 15, and the reinforcing portions 16 are formed, and the resist layer is removed to obtain the structure shown in FIG.

  Thereafter, when the above pedestal is not required, it may be separated into semiconductor acceleration sensors composed of individual sensor chips 1 by a dicing process. When the above pedestal is required, the SOI wafer 20 and the pedestal What is necessary is just to isolate | separate into each semiconductor acceleration sensor by a dicing process, after adhering to a glass substrate by anodic bonding.

  Then, the above-described semiconductor acceleration sensor may be mounted on a base member or a circuit board, and electrodes provided on the base member or the circuit board may be appropriately connected to the pads of the sensor chip 1.

  In the above manufacturing method, it is possible to manage the thickness dimension of each bent portion 13 and each stopper piece 15 with high accuracy by using the insulating layer 22 as an etching stopper layer when performing the back surface side patterning step. Thus, the yield can be improved, and as a result, the cost can be reduced. Further, when the weight portion 12 is formed, the portion corresponding to the slit 14 and the bent portion 13 in the SOI wafer 20 is etched substantially vertically from the back surface side until reaching the insulating layer 22 by an inductively coupled plasma type dry etching apparatus. Therefore, as compared with the case where the weight portion 12 ′ is formed by using anisotropic etching of silicon using an alkaline solution such as KOH as in the above-mentioned Patent Document 1, the space between the associated portion 12 b and the frame portion 11 is smaller. Thus, the width of the slit 14 formed on the sensor chip 1 can be reduced, and the sensor chip 1 can be downsized.

  In the sensor chip 1 described above, each reinforcing portion 16 that reinforces each stopper piece 15 is integrally projected from each corner portion 11 a of the frame portion 11, so that each stopper piece 15 is provided by the reinforcing portion 16. It will be reinforced, it can suppress that the stopper piece 15 is damaged by the impact at the time of the incidental part 12b of the weight part 12 colliding with the stopper piece 15, and can improve impact resistance compared with the past. .

  Further, in the sensor chip 1 described above, each reinforcing portion 16 is formed along the facing direction of each stopper piece 15 and each associated portion 12b on the surface of each stopper piece 15 facing each associated portion 12b. Therefore, the stopper piece 15 can be effectively reinforced while the area of the stopper piece 15 overlapping the reinforcing portion 16 is relatively small, and the area of the stopper piece 15 overlapping the accompanying portion 12b is compared. It is possible to suppress the breakage of the stopper piece 15 while making it larger.

  Further, since the chamfered portion 17 is formed between the inner side surface of the frame portion 11 and the side surface of the reinforcing portion 16, the sensor chip 1 has a frame when the associated portion 12 b of the weight portion 12 collides with the stopper piece 15. When the stress can be suppressed from concentrating on the connecting portion between the inner surface of the portion 11 and the side surface of the reinforcing portion 16, the damage of the reinforcing portion 16 due to the stress concentration can be suppressed, and the chamfered portion 17 is not formed. Compared with impact resistance. The chamfered portion 17 in the present embodiment is formed in a curved surface that is smoothly continuous with the inner surface of the frame portion 11 and the side surface of the reinforcing portion 16, but the shape of the chamfered portion 17 is limited to a curved surface. Instead, for example, as shown in FIGS. 3A and 3B, the angle formed with the inner surface of the frame portion 11 is approximately 135 degrees and the angle formed with the side surface of the reinforcing portion 16 is approximately 90 degrees. If the chamfered portion 17 having the shape shown in FIGS. 3A and 3B is formed, the mechanical strength of each corner portion 11a of the frame portion 11 is increased. Impact resistance against acceleration in the diagonal direction of the rectangular opening window of the frame portion 11 is improved. Further, as shown in FIGS. 4A and 4B, for example, the chamfered portion 17 includes a flat surface 17a having an obtuse angle with the inner surface of the frame portion 11, and the side surfaces of the flat surface 17a and the reinforcing portion 16, respectively. 3 may be formed by an obtuse flat surface 17b, and when the chamfered portion 17 having the shape shown in FIGS. 4A and 4B is formed, FIGS. Compared with the case where the chamfered portion 17 of b) is formed, stress can be prevented from concentrating in the vicinity of the boundary between the reinforcing portion 16 and the chamfered portion 17, and the diagonal line of the rectangular opening window of the frame portion 11 can be prevented. Impact resistance against acceleration in a direction deviating from the direction is improved. 4 (a) and 4 (b), the chamfered portion 17 is constituted by two planes 17a and 17b. However, the chamfered portion 17 is formed by a plurality of planes in which the angle between adjacent planes is an obtuse angle. May be.

  By the way, in the conventional semiconductor acceleration sensor shown in FIGS. 10A and 10B described above, a part of the accompanying portion 12b ′ overlaps in the thickness direction of the bending portion 13 ′. There is a risk that the bending portion 13 'may be damaged when the accompaniment portion 12b' collides with the thin bending portion 13 'due to the acceleration, but in the sensor chip 1 of the present embodiment, the thickness direction of the bending portion 13 is likely to be damaged. Since the bending part 13 and the accompanying part 12 do not overlap with each other, it is possible to avoid the accompanying part 12b from colliding with the bending part 13.

  Further, in the conventional semiconductor acceleration sensor shown in FIGS. 10A and 10B described above, when excessive acceleration acts in the z-axis direction, the weight of the weight portion 12 ′ is reduced by the stopper piece 15 ′ or the pedestal 2 ′. Although the amount of displacement is limited, when excessive acceleration is applied in the x-axis direction or the y-axis direction, it can be displaced until the associated portion 12b ′ contacts the frame portion 11 ′. If excessive acceleration is applied in the y-axis direction, the flexure 13 'may be damaged.

  On the other hand, in the sensor chip 1 of the present embodiment, as described above, a predetermined portion is provided between the outer peripheral surface of the associated portion 12b in the weight portion 12 and the concave portion into which the reinforcing portion 16 enters and the side surface of the reinforcing portion 16. Since the concave portion 12c that forms the gap of the interval d1 is provided, the displacement amount of the weight portion 12 in the plane orthogonal to the one surface of the frame portion 11 is limited by the reinforcing portion 16, and the reinforcing portion 16 is In addition to the function of reinforcing the stopper piece 15, it has a function as a stopper for limiting the amount of displacement of the weight portion 12 in a plane orthogonal to the one surface of the frame portion 11, and the impact resistance is further improved. .

  In the sensor chip 1 described above, the concave portion 12c into which the reinforcing portion 16 is inserted is provided in the associated portion 12b of the weight portion 12, but as shown in FIGS. 5 (a) and 5 (b), the corner portion of the frame portion 11 is provided. Two reinforcing portions 16 are integrally projected from 11a, and concave portions 12c into which the two reinforcing portions 16 respectively enter are provided in the accompanying portions 12b of the weight portion 12. From the portion between the two concave portions 12c adjacent to each other in the accompanying portions 12b The protruding portion 12d may enter the recessed portion 16d surrounded by the two reinforcing portions 16 and the connecting portion that connects the two reinforcing portions 16 to each other. The amount of displacement of the weight portion 12 in the plane orthogonal to the surface is limited by the reinforcing portion 16, and in addition to the function of the reinforcing portion 16 reinforcing the stopper piece 15, the surface orthogonal to the one surface of the frame portion 11. Inside It will have a function as a stopper for limiting the displacement of the weight section 12 definitive, impact resistance is further improved. In short, a convex portion provided integrally with at least one of the accompanying portion 12b and the reinforcing portion 16 is provided, and a concave portion is formed on the other side to form a gap having a predetermined interval between the protruding portion, and the predetermined interval is provided between the accompanying portion 12b and the frame. What is necessary is just to set smaller than the space | interval between the parts 11. FIG.

  Further, when two reinforcing portions 16 are provided at each corner portion 11a of the frame portion 11 as shown in FIGS. 5 (a) and 5 (b), the stopper piece 15 is compared to the case where the number of the reinforcing portions 16 is one. Damage is less likely to occur. 5 (a) and 5 (b), two reinforcing portions 16 are provided so as to protrude from each corner portion 11a of the frame portion 11, but the number is not limited to two, and may be plural. Further, in the example shown in FIGS. 5A and 5B, the chamfered portion 17 has the same plane as the example shown in FIGS. 3A and 3B, but the example shown in FIG. It may be a curved shape similar to the above, or may be constituted by a plurality of planes in which the angle between adjacent planes is an obtuse angle as in the example shown in FIGS. 4 (a) and 4 (b).

(Embodiment 2)
The basic configuration of the semiconductor acceleration sensor of the present embodiment is substantially the same as that of the sensor chip 1 described in the first embodiment. As shown in FIGS. 6 to 8, the frame portion 11, the core portion 12a, the associated portion 12b, and the reinforcement Each of the portions 16 is different in that the cross-sectional area is larger toward the one surface side in the direction perpendicular to the thickness direction on the one surface of the frame portion 11. Here, the reinforcing portion 16 of the sensor chip 1 has a cross-sectional shape that gradually increases in the amount of protrusion from the frame portion 11 as it approaches the stopper piece 15 in the z-axis direction, and is orthogonal to the protruding direction of the reinforcing portion 16. It is formed in a shape that gradually increases as the width approaches the stopper piece 15. In short, the reinforcing portion 16 in the present embodiment is formed in a shape in which the cross-sectional area gradually increases as it approaches the stopper piece 15 in the direction orthogonal to the one surface of the frame portion 11. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  Therefore, in the sensor chip 1 of the present embodiment, when the associated portion 12b of the weight portion 12 collides with the stopper piece 15, it is possible to suppress the stress from concentrating on the connection portion of the stopper piece 15 with the reinforcing portion 16 and to reduce the stress. Breakage of the stopper piece 15 due to concentration can be suppressed. Moreover, since the area of the connection part of the stopper piece 15 and the reinforcement part 16 becomes large compared with Embodiment 1, the destruction tolerance of the stopper piece 15 can be improved compared with Embodiment 1. FIG.

  The manufacturing method of the semiconductor acceleration sensor of the present embodiment is substantially the same as the manufacturing method described in the first embodiment, and it is only necessary to appropriately change the etching conditions in the back surface side patterning step. Hereinafter, as an example, the back surface side patterning is performed. The case where an inductively coupled plasma (ICP) type dry etching apparatus is used in the process will be described.

  In general, an inductively coupled plasma etching apparatus is capable of setting an etching condition in which an etching mode for etching an etching target and a deposition mode for depositing an organic substance on a surface to be etched are alternately repeated. This time is set to be relatively longer than the time of the deposition mode, and the etching mode and the deposition mode are alternately repeated, so that substantially vertical etching is possible as in the first embodiment. Here, for example, if the etching conditions are set so that the time of the etching mode gradually decreases and the time of the deposition mode gradually increases between the start and end of the back side etching process, the frame portion 11 The core portion 12a, the accompanying portion 12b, and the reinforcing portion 16 each have a cross-sectional area that increases toward the one surface side in the direction perpendicular to the thickness direction on the one surface of the frame portion 11, and the inner surface of the frame portion 11, the core portion Tapered etching in which the outer peripheral surface of 12a, the outer peripheral surface of the associated portion 12b, and the side surfaces of the reinforcing portion 16 are each tapered is possible.

(Embodiment 3)
The basic configuration of the semiconductor acceleration sensor of the present embodiment is substantially the same as that of the sensor chip 1 described in the first embodiment. As shown in FIG. 9, the portions of the stopper pieces 15 that do not overlap the reinforcing portion 16 are arranged in the thickness direction. The difference is that a large number of fine holes 18 are formed. The fine hole 18 is formed in a circular hole shape, and the inner diameter is set to a value of about 2 to 3 μm, but the shape of the fine hole 18 is not particularly limited. Here, in the semiconductor acceleration sensor of the present embodiment, each stopper piece 15 is bent due to the formation of a large number of fine holes 18 in each stopper piece 15 as compared to the case where the fine holes 18 are not formed. It becomes easier and more difficult to break. The fine holes 18 are used as holes for introducing an etching solution when unnecessary portions of the insulating layer 22 are removed by etching after the surface side etching step in the manufacturing method described in the first embodiment. The distance between the centers of the adjacent micro holes 18 in a plane orthogonal to the one surface of the portion 11 is set to a constant value, and the distance between the periphery of the stopper piece 15 and the center of the micro hole 18 in the vicinity of the peripheral edge is set. The value is set to half of the above constant value. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  The manufacturing method of the semiconductor acceleration sensor of the present embodiment is substantially the same as the manufacturing method described in the first embodiment, and an etching mask used in the surface side patterning process is formed in the micro holes 18 on the main surface side of the SOI wafer 20. The only difference is that the corresponding part is formed so as to be exposed, and the fine hole 18 is formed in the surface side patterning step.

  By the way, in the manufacturing method described in the first embodiment, when the size of the stopper piece 15 is increased, when the unnecessary portion of the insulating layer 22 is removed by etching after the surface side etching step, the thickness of the insulating layer 22 is reduced. The over-etching time from the point of time when etching that is just etching (so-called just etching) is performed becomes longer, and the side etching amount of the portions that become the frame portion 11, the core portion 12 a, and the reinforcing portion 16 in the insulating layer 22 increases. The impact resistance of the sensor chip 1 may be reduced.

  On the other hand, in the manufacturing method of the present embodiment, an unnecessary portion of the insulating layer 22 that overlaps with the portion that becomes the stopper piece 15 in the silicon layer 23 is also etched by the etching solution introduced through the micro holes 18. (That is, when the unnecessary portion of the insulating layer 22 is removed by etching, the area of the insulating layer 22 in contact with the etching solution is increased), so the overetching time is shortened compared to the manufacturing method described in the first embodiment. The impact resistance of the sensor chip 1 can be improved.

  In addition, you may form the fine hole 18 in the stopper piece 15 in the semiconductor acceleration sensor of Embodiment 2 similarly to this embodiment.

Embodiment 1 is shown, (a) is a schematic plan view, (b) is a schematic cross-sectional view along AA ′ of (a), (c) is a schematic cross-sectional view along BB ′ of (a), and (d) is a schematic cross-sectional view of (a). CC 'schematic sectional drawing of (a), (e) is a schematic bottom view. It is a main process cross section for demonstrating the manufacturing method same as the above. The other example of a structure same as the above is shown, (a) is a principal part schematic plan view, (b) is a principal part schematic bottom view. The other example of a structure same as the above is shown, (a) is a principal part schematic plan view, (b) is a principal part schematic bottom view. The other example of a structure same as the above is shown, (a) is a principal part schematic plan view, (b) is a principal part schematic bottom view. Embodiment 2 is shown, (a) is a schematic plan view, (b) is a schematic cross-sectional view along AA ′ of (a), (c) is a schematic cross-sectional view along BB ′ of (a), and (d) is CC 'schematic sectional drawing of (a), (e) is a schematic bottom view. The same as the above, (a) is a schematic plan view of the main part, and (b) is a schematic bottom view of the main part. FIG. 8 is a schematic cross-sectional view taken along the line D-D ′ of FIG. Embodiment 3 is shown, wherein (a) is a schematic plan view, (b) is a schematic cross-sectional view along AA ′ of (a), (c) is a schematic cross-sectional view along BB ′ of (a), and (d) is CC 'schematic sectional drawing of (a), (e) is a schematic bottom view. A prior art example is shown, (a) is a schematic perspective view, (b) is a schematic sectional view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor chip 11 Frame part 12 Weight part 12a Core part 12b Associated part 12c Recessed part 13 Deflection part 14 Slit 15 Stopper piece 16 Reinforcement part 17 Chamfering part

Claims (6)

  A semiconductor acceleration in which a weight portion arranged in a rectangular opening window of a frame-like frame portion is swingably supported on the frame portion via a thin flexible portion having flexibility on one surface side of the frame portion. The weight part is a sensor, a core part having one end connected to the inner side surface of the frame part and the other end part of the bending part being connected to the outer side, and a core part and the frame part formed integrally with the core part. A thin-walled stopper that limits the amount of displacement of the accompanying part toward the one surface side by being separated from the accompanying part in a direction orthogonal to the one surface. A semiconductor acceleration sensor characterized in that a piece is integrally projected from a corner portion, and a reinforcing portion for reinforcing the stopper piece is integrally projected on the surface of the stopper piece facing the associated portion.   2. The semiconductor according to claim 1, wherein the reinforcing portion is formed along a direction in which the stopper piece and the accompanying portion face each other on a surface of the stopper piece facing the accompanying portion. Acceleration sensor.   The semiconductor acceleration sensor according to claim 1, wherein a chamfered portion is formed between an inner surface of the frame portion and a side surface of the reinforcing portion.   4. The reinforcing member according to claim 1, wherein the reinforcing portion is formed in a shape in which a cross-sectional area gradually increases as it approaches the stopper piece in a direction orthogonal to the one surface of the frame portion. A semiconductor acceleration sensor according to claim 1.   The weight portion is provided with a concave portion that is a concave portion into which the reinforcing portion is inserted and that forms a gap with a predetermined interval between the reinforcing portion and a side surface of the reinforcing portion. The semiconductor acceleration sensor according to claim 1, wherein the semiconductor acceleration sensor is set to be smaller than an interval between the frame and the frame portion.   A convex portion provided integrally with at least one of the accompanying portion and the reinforcing portion enters, and a concave portion is formed on the other side to form a gap with a predetermined interval between the convex portion, and the predetermined interval is provided between the accompanying portion and the auxiliary portion. 5. The semiconductor acceleration sensor according to claim 1, wherein the semiconductor acceleration sensor is set to be smaller than an interval between the frame portion and the frame portion.

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