JP4014888B2 - Semiconductor acceleration sensor and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor acceleration sensor capable of measuring acceleration caused by an external force applied or gravitational acceleration applied in a stationary state by tilting, and a method of manufacturing the same.
[0002]
[Prior art]
An acceleration sensor body formed by etching the semiconductor crystal substrate so as to leave a flexible portion between the weight fixing portion and the cylindrical support portion; a weight fixed to the weight fixing portion; 2. Description of the Related Art A semiconductor acceleration sensor is known that includes a cylindrical pedestal that is disposed so as to surround a weight and supports a support portion. This type of semiconductor acceleration sensor is formed in a flexible part by moving a weight due to a force based on gravitational acceleration applied in a stationary state by accelerating or tilting by an externally applied force and distorting the flexible part. The sensor element detects acceleration corresponding to the amount of strain. However, in such a semiconductor acceleration sensor, since the thickness dimension of the flexible portion of the acceleration sensor main body is small, the flexible portion may be damaged depending on the amount of force applied to the semiconductor acceleration sensor. Therefore, it has been proposed that the gap formed between the weight and the pedestal is set to several μm so that the weight and the pedestal easily come into contact so that the weight is not displaced more than necessary. Further, it has been proposed that the entire semiconductor acceleration sensor is placed in a sealed container filled with a cushioning material made of silicon oil to buffer the force applied to the flexible portion.
[0003]
[Problems to be solved by the invention]
However, it is technically difficult to form the gap formed between the weight and the pedestal so as to have a very small dimension of several μm, which is not suitable for mass production. In addition, if the entire semiconductor acceleration sensor is placed in a sealed container filled with a cushioning material made of silicone oil, the sensor element is easily affected by temperature changes due to silicone oil, and the accuracy of the sensor element is reduced. It was.
[0004]
An object of the present invention is to provide a semiconductor acceleration sensor and a method for manufacturing the same that can prevent damage to a flexible portion without lowering the accuracy of a sensor element or making it difficult to manufacture the sensor element.
[0005]
[Means for Solving the Problems]
The semiconductor acceleration sensor to be improved by the present invention is a semiconductor acceleration sensor in which a weight fixing part is provided at the center, a cylindrical support part is provided at the outer peripheral part, and a flexible part is left between the weight fixing part and the support part. An acceleration sensor main body, a weight, and a pedestal, which are formed by etching a crystal substrate and have a sensor element formed in a flexible portion, are provided. The weight has a shape such that one end is fixed to the weight fixing portion and the other end is located outside the space surrounded by the support portion. The pedestal has a cylindrical shape surrounding the periphery of the weight protruding from the acceleration sensor main body so as to allow the weight to move by a force based on the acceleration acting on the weight while supporting the support portion. In addition, in the gap formed between the weight and the pedestal, a cushioning material that does not significantly restrain the movement of the weight and prevents the flexible portion of the acceleration sensor body from being damaged by the movement of the weight. Has been placed. In the semiconductor acceleration sensor of the present invention, the cushioning material is disposed in the gap so as not to seal the space surrounded only by the gap formed between the weight and the pedestal and surrounded by the support portion. In the semiconductor acceleration sensor of the present invention, when the weight tries to move largely due to the force based on the acceleration, the movement of the weight is suppressed by the buffer material disposed in the gap between the weight and the pedestal. The weight does not move more than necessary, and damage to the flexible part can be prevented. Therefore, according to the present invention, it is not necessary to form the gap formed between the weight and the pedestal in a small size as in the prior art, and manufacturing can be easily performed. Further, since the cushioning material is located only in the gap formed between the weight and the pedestal, the sensor element is not affected by the temperature change by the cushioning material as in the prior art. It is possible to prevent a decrease in accuracy. In addition, since the buffer material is arrange | positioned so that the space enclosed by the support part may not be sealed, the motion of a flexible part is not impaired by arrangement | positioning of a buffer material.
[0006]
The cushioning material is preferably composed of a plurality of partial cushioning portions arranged at positions where the distortion of the flexible portion caused by the movement of the weight is not unbalanced depending on the direction of acceleration applied to the weight.
[0007]
In the state where the force based on acceleration is not applied to the weight, the pedestal has a Z-axis direction that extends in the direction in which the weight fixing portion and the weight are aligned through the center of the weight fixing portion and the weight, respectively. Allowing the weight to be displaced in the triaxial direction by the force based on the acceleration acting on the weight, assuming the triaxial direction in which the two directions orthogonal to the Z-axis direction are the X-axis direction and the Y-axis direction. Thus, the support portion can be supported. In this case, the plurality of partial buffering portions are arranged at portions corresponding to the virtual X axis extending in the X axis direction and the virtual Y axis extending in the Y axis direction in the gap formed between the weight and the pedestal. preferable. In this way, the acceleration applied in the X-axis direction and the Y-axis direction can be accurately measured, and the number and amount of cushioning materials can be reduced.
[0008]
Such a buffer material can be formed from, for example, a gel substance. In this case, the weight and the pedestal have a width dimension of a plurality of gap portions (hereinafter referred to as buffer portion arrangement portions) in which a plurality of partial buffer portions are arranged in a gap formed between the weight and the pedestal. It is preferable to form in a shape smaller than the width dimension of the other gap portion. If the gel substance is placed in a gap where the gap dimensions are not uniform, the gel substance is likely to move from a gap part with a larger dimension to a smaller gap part. If it is made small, the buffer material from a gel-like substance can be easily arrange | positioned in a buffer part arrangement | positioning part.
[0009]
In this case, it is preferable that the width dimension of the buffer portion arrangement portion is 0.01 mm to 0.1 mm, and the gel substance is urethane gel or silicon gel. If the width dimension of the buffer portion arrangement portion is less than 0.01 mm, it is difficult to form the buffer portion arrangement portion. Moreover, if the width dimension of the gap | interval of a buffer part arrangement | positioning part exceeds 0.1 mm, there exists a possibility that a buffer material (silicon gel) may fall out from the inside of a buffer part arrangement | positioning part.
[0010]
When the force based on acceleration acts toward the side opposite to the side where the weight is located with respect to the acceleration sensor main body, the amount of movement when the weight moves is particularly large. Therefore, it is preferable to further include a stopper structure that regulates the amount of displacement of the weight in the triaxial direction within a predetermined range. For example, the weight has an upper surface portion facing the flexible portion, a side surface portion extending in parallel with the virtual Z axis, and an inclined surface portion extending over the upper surface portion and the side surface portion, and the pedestal faces the side surface portion. It can comprise so that it may have an opposing inner surface part and the opposing inclined surface part which opposes an inclined surface part. In this case, the cushioning material is disposed in the gap between the side surface portion and the opposed inner surface portion, and the inclined surface portion forms a first stopper surface constituting a part of the stopper structure, and the opposed inclined surface portion forms the stopper structure. A second stopper surface that constitutes a part and faces the first stopper surface at the time of regulation is formed opposite to the first stopper surface. The first and second stopper surfaces are formed so as to approach a virtual Z axis extending in the Z axis direction toward the side where the acceleration sensor main body is located, respectively, continuously in the circumferential direction or at an interval. It forms as an inclined surface. If it does in this way, in addition to suppression of a shock absorbing material, the movement of a weight will be controlled by mutual contact of a weight and a base, and damage to a flexible part can be prevented more certainly.
[0011]
The cushioning material of the semiconductor acceleration sensor of the present invention is located only in the gap and disposed by applying liquid silicon over the weight and the base so as not to seal the space, and the liquid silicon is heated and cured. Silicon may be formed by gelation. In this way, the buffer material can be easily arranged in the semiconductor acceleration sensor.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a semiconductor acceleration sensor according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the line II-II of FIG. As shown in both drawings, the semiconductor acceleration sensor of the present embodiment has an acceleration sensor main body 1, a weight 3 and a pedestal 5. The acceleration sensor main body 1 includes a semiconductor crystal substrate such that a weight fixing portion 7 at the center, a cylindrical support portion 9 at the outer peripheral portion, and a flexible portion 11 is left between the weight fixing portion 7 and the support portion 9. Is formed by etching. A sensor element (not shown) is formed on the surface (front surface) of the flexible portion 11 opposite to the side where the weight fixing portion 7 and the support portion 9 are located. This sensor element extends in the direction in which the weight fixing portion 7 and the weight 3 are arranged through the weight fixing portion 7 and the center C of the weight 3 in a state where a force based on acceleration is not applied to the weight 3. Assuming a three-axis direction in which the direction is the Z-axis direction and the two directions orthogonal to the Z-axis direction are the X-axis direction and the Y-axis direction, the virtual X-axis lines XL and Y-axis directions extending in the X-axis direction X-axis direction acceleration detecting diffusion resistor, Y-axis direction acceleration detecting diffusion resistor, and Z-axis direction acceleration detecting diffusion resistor for detecting acceleration in the direction of the extending virtual Y-axis line YL and virtual Z-axis line ZL extending in the Z-axis direction, respectively It is composed of The semiconductor acceleration sensor according to the present embodiment has a sensor element in which the weight 3 moves and the flexible portion 11 is distorted by the acceleration based on the force applied from the outside or the force based on the gravitational acceleration applied in a tilted stationary state. The resistance value of each diffused resistor that constitutes s changes to detect the acceleration corresponding to the amount of strain.
[0013]
As shown in FIGS. 3A and 3B, the weight 3 is made of tungsten, and is external to a space in which one end is fixed to the weight fixing portion 7 and the other end is surrounded by the support portion 9. Is located. The weight 3 is integrally formed by a cylindrical main body 3a and four protrusions 3b projecting in a direction in which the virtual X axis XL and the virtual Y axis YL extend from the side surface of the main body 3a toward the base 5. Has been. The main body portion 3a has a circular upper surface portion 3c facing the flexible portion 11, and the weight fixing portion 7 is fixed at the center of the upper surface portion 3c. The projecting portion 3b includes an opposing curved surface 3d having a circular cross section projecting toward the pedestal 5 in the vicinity of the virtual X axis XL or the virtual Y axis YL, and a dent from the pedestal 5 side located on both sides of the opposing curved surface 3d. The cross section has two side curved surfaces 3e and 3e each having an arc shape, and an inclined surface portion 3f formed between the opposing curved surface 3d and the side curved surface 3e and the upper surface portion 3c. . The opposed curved surfaces 3d are formed such that the four opposed curved surfaces 3d are positioned on the same virtual circle concentric with the upper surface portion 3c. The side curved surface 3e is curved so as to form one arc together with the side curved surface 3e of the adjacent protruding portion 3b. In the present embodiment, the opposing curved surface 3d and the side curved surface 3e form a side surface portion 3g extending parallel to the virtual Z axis ZL. The inclined surface portion 3f is inclined so as to approach the virtual Z-axis line ZL toward the side where the acceleration sensor main body 1 is located.
[0014]
As shown in FIGS. 1 and 2, the pedestal 5 is formed of glass, and has a cylindrical shape in which the outer peripheral side contour of the cross section is square and the inner peripheral side contour is circular. Yes. The pedestal 5 supports the support portion 9 so as to allow the weight 3 to be displaced in the three axial directions of the X axis, the Y axis, and the Z axis by a force based on the acceleration acting on the weight 3 and the weight. The weight 3 is arranged to surround the weight 3 so as to allow the weight 3 to move by a force based on the acceleration acting on the weight 3. As a result, a gap 13 is formed between the weight 3 and the base 5. The inner peripheral portion of the pedestal 5 includes an opposed inner surface portion 5a facing the side surface portion 3g of the weight 3, an opposed inclined surface portion 5b facing the inclined surface portion 3f of the weight 3 and contacting the inclined surface portion 3f during regulation. have. Similarly to the inclined surface portion 3f, the opposing inclined surface portion 5b is inclined so as to approach the virtual Z axis ZL toward the side where the acceleration sensor main body 1 is located, and has a truncated conical shape. In a state where no acceleration is applied to the weight 3, the gap between the opposing inclined surface portion 5 b and the inclined surface portion 3 f is formed to be substantially equal in the circumferential direction. In the present embodiment, the acute angle θ at which the virtual surface extending from the inclined surface portion 3f or the opposing inclined surface portion 5b intersects the virtual Z axis ZL is preferably 30 ° to 60 °. In the present embodiment, a first stopper surface and a second stopper surface are constituted by the inclined surface portion 3f and the opposed inclined surface portion 5b, and the weight 3 is formed by the first stopper surface and the second stopper surface. A stopper structure that restricts the amount of displacement in the triaxial direction within a predetermined range is configured.
[0015]
As described above, the opposing curved surface 3d of the weight 3 protrudes toward the pedestal 5 in the vicinity of the virtual X axis XL or the virtual Y axis YL, so that it is in the vicinity of the position corresponding to the virtual X axis XL and the virtual Y axis YL. The width dimension L1 of the gap portion 13a between the opposed inner surface portion 5a of the pedestal 5 and the opposed curved surface 3d of the weight 3 is smaller than the width dimension of the gap portions of other portions. In the present embodiment, the width L1 of the gap portion 13a is 0.01 mm to 0.1 mm. In the gap portion 13a, a cushioning material 15 composed of four partial cushioning portions 15A to 15D is arranged at equal intervals in the circumferential direction of the weight 3. In other words, the width dimension L1 of the four gap portions (buffer portion arrangement portions) 13a in which the four partial buffer portions 15A to 15D are arranged in the gap 13 is formed to be smaller than the width dimensions of the other gap portions. Has been. The four partial buffer portions 15A to 15D are formed of a gel-like substance made of silicon gel, and the movement of the weight 3 is not significantly restricted, and the flexible portion 11 of the acceleration sensor main body 1 is moved by the movement of the weight 3. It has enough elasticity and flexibility to prevent damage. These partial buffering portions 15A to 15D are arranged so as to be joined only to both the weight 3 and the pedestal 5 so as not to seal the space surrounded only by the gap portion 13a and surrounded by the support portion 9. In the present embodiment, liquid silicone sold under the trade name of silicone gel KE1055 from Shin-Etsu Silicon Co., Ltd. is disposed at a predetermined position in the gap portion 13a by coating or the like, and this liquid silicon is heated at 150 ° C. for 1 hour. The liquid silicon was cured to form the buffer material 15 made of silicon gel.
[0016]
In the semiconductor acceleration sensor of the present embodiment, when the weight 3 tries to move greatly due to the force based on the acceleration, the movement of the weight 3 is suppressed by the buffer material 15, so that the weight 3 moves more than necessary. In addition, damage to the flexible portion 11 can be prevented. Therefore, unlike the prior art, it is not necessary to form the gap 13 formed between the weight 3 and the pedestal 5 with a small size, and the semiconductor acceleration sensor can be easily manufactured. Further, since the cushioning material 15 is located only in the gap 13, the sensor element is not affected by the temperature change by the cushioning material 15 as in the prior art, and prevents the accuracy of the sensor element from being lowered. be able to.
[0017]
FIG. 4 is a cross-sectional view of a semiconductor acceleration sensor according to another embodiment of the present invention. Since the semiconductor acceleration sensor of the present embodiment has the same structure as the semiconductor acceleration sensor shown in FIG. 1 except for the shape of the pedestal 25, the same member as the semiconductor acceleration sensor shown in FIG. A reference numeral 20 is added to the reference numeral, and the description thereof is omitted. In the present embodiment, the pedestal 25 has a cylindrical shape in which the outer peripheral side contour of the cross section is square and the inner peripheral side contour is octagonal. The opposed inner surface portion 25a of the pedestal 25 intersects with the virtual X axis line XL or the virtual Y axis line YL and intersects with the four opposed curved surfaces 23d of the weight 23 so as to face the virtual opposed axial surfaces 25c. There are four non-axially facing surfaces 25d that face the four side curved surfaces 23e of the weight 23 without intersecting the X axis line XL or the virtual Y axis line YL. The opposed inclined surface portion (portion corresponding to reference numeral 5b in FIG. 1) facing the inclined surface portion (portion corresponding to reference numeral 3f in FIG. 1) of the weight 23 of the pedestal 25 has a truncated octagonal pyramid shape. ing.
[0018]
As described above, the axially opposing surface 25c is orthogonal to the virtual X axis XL or the virtual Y axis YL, and the opposing curved surface 23d of the weight 23 protrudes toward the pedestal 25 near the virtual X axis XL or the virtual Y axis YL. Therefore, the width dimension of the gap 33 between the weight 23 and the pedestal 25 becomes smaller as it approaches the virtual X axis XL or the vicinity of the virtual Y axis YL. In other words, as the width dimension of the four gap portions (buffer portion arrangement portions) 33a in which the four partial buffer portions 35A to 35D are arranged in the gap 33 approaches the virtual X axis XL or the vicinity of the virtual Y axis YL, The weight 23 and the pedestal 25 are formed in a shape smaller than the width dimension of the gap part, and the width dimension L2 of the minimum part is 0.01 mm to 0.1 mm. In the semiconductor acceleration sensor of the present embodiment, when the liquid silicone is disposed in the gap 33 by coating or the like, the liquid silicon can be disposed closer to the virtual X axis XL or the virtual Y axis YL.
[0019]
The weight and the pedestal are not limited to the shapes in the above example, and various shapes can be adopted. For example, the pedestal can be formed in a shape in which a portion near the virtual X axis line XL or the virtual Y axis line YL on the inner peripheral side of the pedestal protrudes toward the weight side.
[0020]
In the above example, the stopper structure including the inclined surface portion 3f and the opposing inclined surface portion 5b is provided, but it is needless to say that the stopper structure may not be provided.
[0021]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the semiconductor acceleration sensor which can prevent damage to a flexible part can be obtained easily, without reducing the precision of a sensor element.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a semiconductor acceleration sensor according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line II-II in FIG.
FIGS. 3A and 3B are a side view and a plan view of a weight of the semiconductor acceleration sensor shown in FIG.
FIG. 4 is a cross-sectional view of a semiconductor acceleration sensor according to another embodiment of the present invention.

Claims (3)

The semiconductor crystal substrate is formed by etching so as to leave a weight fixing portion at the center, a cylindrical support portion at the outer peripheral portion, and a flexible portion between the weight fixing portion and the support portion, and An acceleration sensor body in which a sensor element is formed in the flexible part;
A weight having a shape and dimensions such that one end is fixed to the weight fixing portion and the other end is located outside the space surrounded by the support portion;
A cylindrical pedestal surrounding the weight projecting from the acceleration sensor main body so as to allow the weight to move by a force based on acceleration acting on the weight and supporting the support portion; Equipped,
In the gap formed between the weight and the pedestal, the movement of the weight is not significantly restricted, and the movement of the weight prevents the flexible part of the acceleration sensor body from being damaged. A semiconductor acceleration sensor in which a cushioning material is disposed,
The cushioning material is composed of a plurality of partial cushioning portions located only in the gap and disposed in the gap so as not to seal the space ,
The pedestal has a direction extending in a direction in which the weight fixing portion and the weight are aligned through the center of the weight fixing portion and the weight, respectively, in a state where a force based on acceleration is not applied to the weight. Assuming a three-axis direction in which the Z-axis direction and two directions orthogonal to the Z-axis direction are the X-axis direction and the Y-axis direction, the weight is caused by the force based on the acceleration acting on the weight. The support part is supported so as to allow displacement in three axial directions,
The plurality of partial buffering portions are disposed in a plurality of gap portions in the gap located on a virtual X axis extending in the X axis direction and a virtual Y axis extending in the Y axis direction,
The plurality of partial buffer portions are formed of a gel-like substance ;
The weight and the pedestal have a shape in which the width dimension of the plurality of gap portions in which the plurality of partial buffer portions are arranged in the gap is smaller than the width dimension of other gap portions. Sensor. The width dimension of the plurality of gap portions in which a plurality of partial buffering portion is disposed is 0.01 mm to 0.1 mm, a semiconductor acceleration sensor according to claim 1 wherein the gel material is a urethane gel or a silicone gel. A stopper structure for restricting the amount of displacement of the weight in the three-axis direction within a predetermined range;
The weight includes an upper surface portion facing the flexible portion, a side surface portion extending in parallel with the virtual Z axis, and an inclined surface portion extending over the upper surface portion and the side surface portion.
The pedestal has an opposed inner surface portion that faces the side surface portion, and an opposed inclined surface portion that faces the inclined surface portion,
The cushioning material is disposed in a gap between the side surface portion and the opposed inner surface portion,
A first stopper surface constituting a part of the stopper structure is formed by the inclined surface portion,
A second stopper surface that forms a part of the stopper structure by the opposed inclined surface portion and is opposed to the first stopper surface and contacts the first stopper surface at the time of regulation,
Each of the first and second stopper surfaces is formed continuously in the circumferential direction or at an interval so as to approach a virtual Z axis extending in the Z axis direction toward the side where the acceleration sensor body is located. The semiconductor acceleration sensor according to claim 1 , wherein the semiconductor acceleration sensor is formed as an inclined surface that is inclined.

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