JP2001242191A - Semiconductor acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor acceleration sensor for improving a yield and reducing cost by securing the movable range of a weight part without forming any recessed parts in a glass stopper and at the same time, eliminating spot facing machining for forming the recessed parts. SOLUTION: The semiconductor acceleration sensor is provided with a weight part 10 that is supported by a support 11 where it can be rocked freely via a deflection part 12, a semiconductor acceleration sensor chip that has a piezo resistor 3 for detecting distortion being generated in the deflection part 12 due to the rocking of the weight part 10 at the deflection part 12 and detects acceleration based on the change in the resistance of the piezoresistor 3, and stoppers 6 and 7 for suppressing the excessive displacement of the weight part 10, while they are jointed to the semiconductor acceleration sensor chip. The semiconductor acceleration sensor forms a step part 10a at the weight part 10, to reduce the thickness near the tip part of the weight part 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor acceleration sensor for detecting acceleration.

[0002]

2. Description of the Related Art In recent years, acceleration sensors have been widely used in various industrial fields such as automobiles. Above all, the use of semiconductor acceleration sensors in in-vehicle relations, home electric appliances and the like is rapidly increasing in terms of reliability, cost, and reduction in size and weight.

FIG. 1 shows a conventional semiconductor acceleration sensor.
3 will be described. Semiconductor substrate 1 (silicon substrate 1)
A weight portion 10 and a bending portion 12 that supports the weight portion 10 in a swingable manner with a thin beam structure, and a piezoresistor 3 that detects distortion generated in the bending portion is formed in the bending portion 12. Have been. In this structure, the piezoresistor 3 converts the stress of the distortion generated in the bending portion 12 when the weight portion 10 swings by receiving the acceleration into an electric signal, and outputs the electric signal to the outside from the aluminum pad 5 for wire bonding. In addition, bending portion 1
The upper glass stopper 6 is anodically bonded to the upper surface (in the figure) of the silicon substrate 1 via the aluminum layer 4 in order to prevent the weight 10 formed at the tip of 2 from moving up and down beyond the allowable range. The lower surface of the silicon substrate 1 is anodically bonded to the lower glass stopper 7.

Here, in order to secure a movable area (space) for swinging (displacement) of the weight portion 10 in the vertical direction, a concave portion is formed in the upper glass stopper 6 and the lower glass stopper 7 by counterbore processing. 8 are provided.

As another conventional example, an upper glass stopper 6 and a lower glass stopper 7 are used to adjust the movable range of the weight portion 10 and control the sensitivity of the semiconductor acceleration sensor.
The protrusion 9 with which the weight contacts may be formed in the concave portion (FIG. 1B). If the upper and lower glass stoppers are flat, the distance between the glass stopper and the silicon wafer will be limited by the thickness of the aluminum pattern for anodic bonding,

[0006]

However, as described above, in order to secure the movable area of the weight portion 10, the upper glass stopper 6 and the lower glass stopper 7 are counterbored to form recesses. The projections 9 need to be formed, but it is difficult to process the glass, and there are problems with yield,
There was a problem that processing cost was high.

The present invention has been made in view of the above circumstances, and has as its object the purpose of forming a concave portion in a stopper (upper glass stopper, lower glass stopper) without forming a concave portion.
It is an object of the present invention to provide a semiconductor acceleration sensor capable of securing a movable range of a weight portion, eliminating counterboring for forming a concave portion, improving yield and reducing cost.

[0008]

In order to achieve the above object, according to the present invention, a weight portion swingably supported by a support portion via a bending portion, and the weight portion is supported by the bending portion. A semiconductor acceleration sensor chip having a piezoresistor for detecting distortion generated in the bending portion due to swinging of the portion, detecting acceleration based on a change in the resistance value of the piezoresistance, and being joined to the semiconductor acceleration sensor chip; A semiconductor acceleration sensor having a stopper for suppressing excessive displacement of the weight portion, wherein a step portion is formed in the weight portion to reduce a thickness near a tip portion of the weight portion. .

According to a second aspect of the present invention, in the semiconductor acceleration sensor according to the first aspect, a protrusion is formed on the step portion.

According to a third aspect of the present invention, in the semiconductor acceleration sensor according to the second aspect, the projection is a plurality of columnar projections.

According to a fourth aspect of the present invention, in the semiconductor acceleration sensor according to the second aspect, the projection is a linear projection formed in parallel with a side of a swinging tip of the weight portion. It is a feature.

According to a fifth aspect of the present invention, in the semiconductor acceleration sensor according to the fourth aspect, the linear projection is formed at a swinging tip of the weight portion.

According to a sixth aspect of the present invention, in the semiconductor acceleration sensor according to any one of the first to fifth aspects, a recess is formed on the step-forming surface or the opposite surface of the weight.

According to a seventh aspect of the present invention, in the semiconductor acceleration sensor according to any one of the first to sixth aspects, a notch is formed in a side wall of the concave portion.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor acceleration sensor according to an embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a semiconductor acceleration sensor according to a first embodiment of the present invention, and is a perspective view particularly showing a weight 10. In the figure, the left end is supported by the bending portion 12, and the right end is a swinging tip. By forming the step 10a, the thickness of the weight portion 10 near the distal end portion is reduced, and the weight portion 10 is formed so as to be thinner than the whole. FIG. 7 (I) shows a diagram in which the weight portion 10 is formed on the silicon substrate 1 and the upper glass stopper 6 and the lower glass stopper are joined to form a semiconductor acceleration sensor. Since the thickness of the tip portion of the weight portion 10 is reduced by the step 10a, even if a flat plate having no recess is formed in the upper glass stopper 5 and the lower glass stopper 6 as shown in the figure, the weight portion 1
An operation area in the vertical direction of 0 can be secured.

As described above, since a step is formed in the weight portion 10 to reduce the thickness near the tip of the weight portion 10, a flat plate in which no concave portion is formed in the upper glass stopper 5 and the lower glass stopper 6 is formed. In this case, the vertical operation area of the weight portion 10 can be secured, and the counterbore processing for forming the concave portion is not required, so that the yield of the semiconductor acceleration sensor can be improved and the cost can be reduced. It works.

FIG. 2 shows a semiconductor acceleration sensor according to a second embodiment of the present invention, and is a perspective view particularly showing the weight 10. In the figure, the left end is supported by the bending portion 12, and the right end is a swinging tip. As in the first embodiment, by forming the step 10a, the thickness of the weight portion 10 near the distal end portion is reduced, and the weight portion 10 is formed to be thinner than the whole. Further, in the present embodiment, two columnar projections 10b are formed on the step 10a. FIG. 8 (I) shows the semiconductor acceleration sensor formed by forming the weight portion 10 on the silicon substrate 1 and joining the upper glass stopper 6 and the lower glass stopper. Since the thickness of the tip portion of the weight portion 10 is reduced by the step 10a, even if a flat plate having no recess is formed in the upper glass stopper 5 and the lower glass stopper 6 as shown in the figure, the weight portion 1
An operation area in the vertical direction of 0 can be secured. Further, the columnar projection 10b performs the same operation as the projection 9 shown in FIG. 13B of the conventional example, and can adjust the movable range of the weight portion 10 to control the sensitivity of the semiconductor acceleration sensor. .

As described above, the step 10a is formed in the weight 10 to reduce the thickness near the tip of the weight 10, and the columnar projection 10b is formed in the step 10a. In addition to the effects of the first embodiment, the weight 1
By adjusting the movable range of 0, the sensitivity of the semiconductor acceleration sensor can be controlled, and processing for forming the projections (9) in the upper glass stopper and the lower glass stopper is not required, thereby improving the yield of the semiconductor acceleration sensor. And an effect that cost reduction can be achieved.

FIG. 3 shows a semiconductor acceleration sensor according to a third embodiment of the present invention, and is a perspective view particularly showing the weight 10. In the figure, the left end is supported by the bending portion 12, and the right end is a swinging tip. As in the first embodiment, by forming the step 10a, the thickness of the weight portion 10 near the distal end portion is reduced, and the weight portion 10 is formed to be thinner than the whole. Further, in the present embodiment, a linear columnar projection 10c is formed on the step 10a in parallel with the side of the swinging tip of the weight 10a. FIG. 9 (m) shows a diagram in which the weight portion 10 is formed on the silicon substrate 1 and the upper glass stopper 6 and the lower glass stopper are joined to form a semiconductor acceleration sensor. Since the thickness of the tip of the weight portion 10 is reduced by the step 10a, the upper glass stopper 5 and the lower glass stopper 6 as shown in FIG.
Even if a flat plate having no concave portion is used, a vertical operating area of the weight portion 10 can be secured. Further, the linear projection 10c acts in the same manner as the projection 9 shown in FIG. 13B of the conventional example, and adjusts the movable range of the weight 10 to control the sensitivity of the semiconductor acceleration sensor. it can. In addition, the linear projection 10c has a weight 10 with a step 10a.
Since it acts so as to wrap the airflow flowing at the time of the swing of 0, an air damping effect of buffering the swing with respect to the weight portion 10 is provided, and the swing range can be optimized.

As described above, the step 10a is formed in the weight portion 10 to reduce the thickness in the vicinity of the tip of the weight portion 10, and the step 10a is formed with respect to the side of the swinging tip of the weight 10a. Since the linear projections 10b are formed in parallel, in addition to the effects of the first and second embodiments, an air damping effect of buffering the swing with respect to the weight 10 is provided, and the swing range is increased. This makes it possible to optimize the value.

FIG. 4 shows a semiconductor acceleration sensor according to a fourth embodiment of the present invention, and is a perspective view particularly showing the weight 10. In the figure, the left end is supported by the bending portion 12, and the right end is a swinging tip. As in the first embodiment, by forming the step 10a, the thickness of the weight portion 10 near the distal end portion is reduced, and the weight portion 10 is formed to be thinner than the whole. Further, in this embodiment, a linear columnar projection 10d is formed on the step 10a in parallel with the side of the swinging tip of the weight portion 10a and at the swinging tip. The height of the linear projection 10d is the same as that of the step 1.
It is necessary to lower the height (depth) of the step of 0a.
FIG. 10 (m) shows the semiconductor acceleration sensor formed by forming the weight portion 10 on the silicon substrate 1 and joining the upper glass stopper 6 and the lower glass stopper. Weight part 1
0 Since the thickness of the leading end portion is reduced by the step 10a and the height of the linear projection 10d is lower than the height (depth) of the step 10a, the upper glass stopper 5 and the Even if a flat plate having no concave portion is used for the lower glass stopper 6, a vertical operating area of the weight 10 can be ensured. Further, the linear projection 10d acts in the same manner as the projection 9 shown in FIG. 13B of the conventional example, and adjusts the movable range of the weight 10 to control the sensitivity of the semiconductor acceleration sensor. it can. In addition, the linear protrusion 10d
Since the step 10a acts to wrap the airflow flowing when the weight portion 10 swings, the air damping effect of buffering the swing with respect to the weight portion 10 is provided, and the swing range can be optimized. It also has an effect. In particular, since the linear projection 10d is formed at the swinging tip of the weight portion 10, it acts so as to enclose more airflow as compared with the third embodiment, so that more effective air damping is achieved. In addition to the effect, the inertial force of the swing of the weight portion 10 is increased, and the sensitivity of acceleration detection can be increased.

As described above, the step 10a is formed in the weight 10 to reduce the thickness near the tip of the weight 10, and the step 10a is formed with respect to the side of the swinging tip of the weight 10a. Since the linear projections 10b are formed in parallel, in addition to the effects of the first, second, and third embodiments, the air damping effect of buffering the swing with respect to the weight 10 is further improved. As a result, the swing range can be optimized. Further, the inertial force of the swing of the weight portion 10 is increased, and the sensitivity of acceleration detection can be increased.

FIGS. 11I and 11M show a semiconductor acceleration sensor according to a fifth embodiment of the present invention. FIG.
FIG. 1 shows the surface of the weight portion 10 where the step 10a is formed, as shown in FIG.
The recess 10e shown in FIG. 1 (e) is formed. As in the first embodiment, since the thickness of the distal end of the weight portion 10 is reduced by the step 10a, a flat plate without a concave portion is formed in the upper glass stopper 5 and the lower glass stopper 6 as shown in the figure. Also, an operating area in the vertical direction of the weight unit 10 can be secured. Further, in the present embodiment, the concave portion 10e
However, since it acts so as to wrap the airflow flowing when the weight portion 10 swings, the air damping effect of buffering the swing with respect to the weight portion 10 is provided, and the swing range can be optimized. Bring.

As described above, the step 10a is formed in the weight 10 and the recess 1 is formed in the surface of the weight 10 where the step 10a is formed.
0e is formed, so that in addition to the effect of the first embodiment, an air damping effect of buffering the swing with respect to the weight portion 10 is provided, and the swing range can be optimized. To play.

FIG. 12 (j) shows a semiconductor acceleration sensor according to a sixth embodiment of the present invention. A recess 10e 'is formed on the opposite surface of the weight 10 from the step 10a where the weight 10 is formed as shown in FIG. 11 (I). As in the first embodiment, since the thickness of the distal end of the weight portion 10 is reduced by the step 10a, a flat plate without a concave portion is formed in the upper glass stopper 5 and the lower glass stopper 6 as shown in the figure. Also, an operating area in the vertical direction of the weight unit 10 can be secured. Further, in the present embodiment, since the concave portion 10e 'acts so as to wrap the airflow flowing when the weight portion 10 swings, the weight portion 10e'
In this case, an air damping effect of buffering the swing is provided, and the swing range can be optimized.

As described above, the step 10a is formed in the weight 10 and the recess 10e 'is formed on the surface of the weight 10 opposite to the step where the step 10a is formed. In addition to the effects of the first embodiment, the weight 10
In this case, an air damping effect of buffering the swing is provided, so that the swing range can be optimized.

FIG. 12 shows a step 10a of the weight 10 of the semiconductor acceleration sensor according to the seventh embodiment of the present invention. A notch 10f is formed in the side wall of the recess 10e according to the sixth embodiment. By releasing the air wrapped in the concave portion 10e by the notch portion 10f, there is an effect that the air damping effect can be finely adjusted.

While the first to seventh embodiments of the present invention have been described above, the manufacturing steps of the first to sixth embodiments will now be described. The upper main surface of the semiconductor substrate (silicon substrate) 1 in the drawing is called an upper surface, and the lower main surface is called a lower surface.

FIGS. 6 and 7 show a manufacturing process (referred to as a first manufacturing process) according to the first embodiment of the present invention. After a silicon oxide film 2 is formed by thermal oxidation on an n-type single crystal silicon substrate 1 having both main surfaces subjected to mirror polishing, the silicon oxide film 2 is patterned at a predetermined position by a photoresist mask 14, and then the silicon oxide film 2 is etched. To remove. Next, a p-type impurity 3a is formed by ion implantation.
Is implanted into the silicon substrate 1 (FIG. 6A), an activation process is performed in an oxidizing atmosphere and a nitrogen atmosphere to form a diffusion resistance wiring (piezo resistor) 3 and a silicon oxide film 2 (FIG. 6B). )).

Next, after a silicon nitride film 15 is formed by a low pressure CVD method, the silicon nitride film 15 is patterned at a predetermined position on the lower surface of the silicon substrate 1 with a photoresist mask 14 (FIG. 6C). The silicon nitride film 15 formed on the lower surface by the etching technique is removed by etching. After the photoresist mask 14 is removed, anisotropic etching is performed using an aqueous solution of potassium hydroxide at 80 ° C. using the silicon nitride film 15 as a mask. At this time, the etching of the silicon substrate 1 does not penetrate the upper surface side (FIG. 6D).

Next, after the photoresist mask 14 at a predetermined position on the silicon substrate 1 is patterned (FIG. 6).
(E)) A portion to be a lower surface of the weight portion 10 in a later step is etched by a dry etching technique. (FIG. 6
(F)). Next, after an aluminum layer 4 is formed on the upper surface of the silicon substrate 1 by a sputtering method or an evaporation method, a predetermined pattern is formed by using
Patterning is performed by dry etching such as E (FIG. 7 (g)).

Next, after a predetermined pattern is formed by the photoresist mask 14 and the silicon nitride film 15 and the silicon oxide film 2 are etched, a part of the silicon substrate 1 is etched from the upper surface by a dry etching technique such as RIE. It is removed (FIG. 7 (h)). Next, after a predetermined pattern is formed by the photoresist mask 14,
A part of the silicon substrate 1 is removed from the upper surface by etching using a dry etching technique such as RIE. At this time,
Since the silicon substrate 1 has a dug portion formed from the lower surface by anisotropic etching, the through hole 13 is formed together with the dry etching from the surface, so that the weight portion 10 for detecting the acceleration is formed. The periphery is cut off from the silicon substrate 1 to be in a cantilever state supported by the thin flexible portion 12 (FIG. 7 (i)).

Next, by removing the photoresist mask 14, a structure having a step 10a formed on the upper surface of the weight 10 is obtained (FIG. 7 (j)). FIG. 7 (k) is a perspective view of the weight portion 10 of FIG. 7 (j).

Next, the aluminum layer 4 and the upper glass stopper 6 on the silicon substrate 1 are connected to each other at a temperature of, for example, 400.degree. Anodic bonding is performed by applying a voltage. Under the same conditions, the silicon substrate 1 and the lower glass stopper 7 are anodically bonded to obtain the structure shown in FIG. At this time, the upper glass stopper 5 is a flat plate,
Although the surface facing the silicon substrate 1 is flat, the weight 10 moves due to the thickness of the aluminum layer 4 to be anodically bonded to the upper glass stopper 5 and the step formed on the surface of the weight formed on the silicon substrate 1. Can be secured. Further, since the lower side of the weight portion 10 is etched, an area where the weight can move can be secured. With this structure, it is not necessary to form a concave portion by performing processing such as counterbore processing on the upper glass stopper 5 and the lower glass stopper 6, so that the manufacturing cost of the semiconductor acceleration sensor can be reduced.

FIGS. 6 and 8 show a manufacturing process (referred to as a second manufacturing process) according to the second embodiment of the present invention. The manufacturing process is basically the same as the first manufacturing process, and the manufacturing process of FIG. 6 is common. However, in the process of etching the upper surface of the weight 10, the columnar projections are formed by changing the pattern of the photoresist mask 14. 10b can be formed (FIG. 8 (h)). The other steps related to the second manufacturing step are the same as those in the first manufacturing step, and a description thereof will be omitted.

FIGS. 6 and 9 show a manufacturing process (referred to as a third manufacturing process) according to the third embodiment of the present invention. The manufacturing process is basically the same as the first manufacturing process, and the manufacturing process of FIG. 6 is common. However, in the process of etching the upper surface of the weight 10, the linear shape is obtained by changing the pattern of the photoresist mask 14. The protrusion 10c can be formed (FIG. 8H). The other steps related to the third manufacturing step are the same as those in the first manufacturing step, and a description thereof will be omitted.

FIGS. 6 and 10 show a manufacturing process (referred to as a fourth manufacturing process) according to the fourth embodiment of the present invention. The manufacturing process is basically similar to the first and third manufacturing processes, and the manufacturing process of FIG. 6 is common. However, in the process of etching the upper surface of the weight 10, the pattern of the photoresist mask 14 is changed (third process). By changing the position of the opening in the manufacturing process (1), a linear projection 10d can be formed (FIG. 10 (h)). The other steps related to the fourth manufacturing step are the same as those in the first manufacturing step, and a description thereof will be omitted.

FIG. 11 shows a manufacturing process (referred to as a fifth manufacturing process) according to the fifth embodiment of the present invention.
N-type single crystal silicon substrate 1 with mirror-polished surfaces on both sides
After the silicon oxide film 2 is formed thereon by thermal oxidation, the silicon oxide film 2 is patterned at a predetermined position by a photoresist 14, and then the silicon oxide film 2 is removed by etching. Next, after the p-type impurity 3a is implanted into the silicon substrate 1 by an ion implantation method (FIG. 11A), activation is performed in an oxidizing atmosphere and a nitrogen atmosphere, and the diffusion resistance wiring (piezo resistance) 3 and the silicon An oxide film 2 is formed (FIG. 11
(B)).

Next, after a silicon nitride film 15 is formed by a low pressure CVD method, patterning is performed at a predetermined position on the lower surface of the silicon substrate 1 with a photoresist mask 14 (FIG. 11C), and a dry process such as RIE is performed. The silicon nitride film 15 formed on the lower surface by the etching technique is removed by etching. After the photoresist mask 14 is removed, anisotropic etching is performed using an aqueous solution of potassium hydroxide at 80 ° C. using the silicon nitride film 15 as a mask. At this time, the etching of the silicon substrate 1 is performed so as not to penetrate the upper surface. However, this etching determines the thickness of the bending portion 12 supporting the weight portion 10, but since the anisotropic etching is performed in a separate step later, the underetching is performed (FIG. 11D).

Next, after patterning the photoresist mask 14 at a predetermined position on the silicon substrate 1, the silicon nitride film 15 and the silicon oxide film 2 are removed by a dry etching technique (FIG. 11E). Next, after the photoresist mask 14 is removed, anisotropic etching is performed using an aqueous solution of potassium hydroxide at 80 ° C. using the silicon nitride film 15 as a mask. At this time, the lower surface of the silicon substrate 1 is also etched at the same time, and the etching time is determined by the thickness of the bent portion 12 and the size of the concave portion formed in the silicon substrate 1. As a result, an anisotropically etched structure is obtained on the upper and lower surfaces of the silicon substrate 1 (FIG. 11).
(F)).

Next, the silicon nitride film 15 and the silicon oxide film 2 formed on the lower surface of the silicon substrate 1 are removed by etching, a photoresist mask 14 is formed at a predetermined position, and the lower surface of the silicon substrate 1 is etched. (FIG. 11 (g)). After that, the photoresist mask 14
Is obtained to obtain the structure shown in FIG.

Next, after the aluminum layer 4 is formed by the sputtering method or the vapor deposition method, a predetermined pattern is formed by the photoresist mask 14, and then the aluminum layer is patterned by dry etching such as RIE (FIG. 1).
1 (i)). Next, after a predetermined pattern is formed using the photoresist mask 14, the upper surface of the silicon substrate 1 is partially etched. By this processing, the height of the distal end of the weight portion 10 becomes slightly lower than that of the support portion side (FIG. 11).
(J)).

Next, after a predetermined pattern is formed by the photoresist mask 14, the silicon substrate 1 is etched from the upper surface to form a dug portion by anisotropic etching from the rear surface formed in FIG. Thus, through holes 13 are formed (FIG. 11 (k)), and the photoresist mask 14 is removed to obtain a structure shown in FIG. 11 (l). At this time, when the silicon substrate 1 is viewed from right above, a concave portion 10e is formed in the center of the weight portion 10 as shown in FIG. When the weight portion 10 swings, air accumulates in the concave portion, so that a damping effect can be obtained.

Next, the aluminum layer 4 and the upper glass stopper 5 on the silicon substrate 1 are connected to each other at a temperature of, for example, 400.degree. Anodic bonding is performed by applying a voltage. Under the same conditions, the silicon substrate 1 and the lower glass stopper 6 are anodically bonded to obtain a structure shown in FIG.

FIG. 12 shows a manufacturing process (referred to as a sixth manufacturing process) of the sixth embodiment of the present invention.
After a silicon oxide film 2 is formed by thermal oxidation on a silicon substrate 1 having both surfaces subjected to mirror polishing, a silicon oxide film is patterned by a photoresist mask 14 at a predetermined position, and then the silicon oxide film is removed by etching. Next, after the p-type impurity 3a is implanted into the silicon substrate 1 by an ion implantation method (FIG. 12A), activation treatment is performed in an oxidizing atmosphere and a nitrogen atmosphere, and the diffusion resistance wiring (piezo resistance) 3 and the silicon An oxide film 2 is formed (FIG. 12B).

Next, after a silicon nitride film 15 is formed by a low pressure CVD method, it is patterned at a predetermined position on the lower surface of the silicon substrate 1 with a photoresist mask 14 (FIG. 12C), and then a dry process such as RIE is performed. The silicon nitride film 15 formed on the lower surface by the etching technique is removed by etching. After the photoresist mask 14 is removed, anisotropic etching is performed using an aqueous solution of potassium hydroxide at 80 ° C. using the silicon nitride film 15 as a mask. At this time, the silicon substrate 1 is etched so as not to penetrate the surface (FIG. 12D).

Next, after a photoresist mask 14 is patterned at a predetermined position on the lower surface of the silicon substrate 1, the silicon substrate 1 is etched by a dry etching technique. (FIG. 12 (e)). Next, after the photoresist mask 14 is patterned at a predetermined position on the lower surface of the silicon substrate 1, the silicon substrate 1 is etched by a dry etching technique. (FIG. 12 (f)). Next, after a photoresist mask is patterned at a predetermined position on the lower surface of the silicon substrate 1, the silicon substrate 1 is etched by a dry etching technique. (FIG. 12 (g)). By these processes, a concave portion 10 e ′ is formed on the lower surface of the weight portion 10 by linear projections having different steps.

Next, after the photoresist mask 14 is removed, an aluminum layer 4 is deposited on the upper surface of the silicon substrate 1 by a sputtering technique or a vapor deposition technique, and a pattern is formed at a predetermined position by the photoresist mask 14. The aluminum layer 4 is removed by an etching technique (FIG. 12H).

Next, after a pattern is formed at a predetermined position on the upper surface of the silicon substrate 1 by using a photoresist mask 14, the silicon substrate 1 is etched. At this time, since the lower surface of the silicon substrate 1 is anisotropically etched with the KOH solution, the through-hole 13 is formed in the silicon substrate 1 (FIG. 12 (i)).

Next, the aluminum layer 4 and the upper glass stopper 5 on the silicon substrate 1 are connected, for example, at a temperature of 400.degree. Anodic bonding is performed by applying a voltage. Under the same conditions, the structure shown in FIG. 12 (j) is obtained by anodic bonding the silicon substrate 1 and the lower glass stopper 6. Since the concave portion 10e 'can be formed on the lower surface of the weight portion 10 by the manufacturing process described above, it is expected that the damping effect and the like can be secured.

[0052]

As described above, according to the first aspect of the present invention, the weight portion swingably supported by the support portion via the bending portion, and the swinging of the weight portion by the bending portion. Having a piezoresistor for detecting distortion generated in the bending portion due to movement,
A semiconductor acceleration sensor chip having a semiconductor acceleration sensor chip for detecting acceleration based on a change in the resistance value of the piezoresistor, and a stopper joined to the semiconductor acceleration sensor chip to suppress excessive displacement of the weight portion; A step is formed in the weight part to reduce the thickness near the tip of the weight part.
It is possible to provide a semiconductor acceleration sensor that can secure the movable range of the weight portion without forming a concave portion on the lower glass stopper), eliminate counterbore processing for forming the concave portion, and improve the yield and reduce the cost.

According to the second aspect of the present invention, since the projection is formed on the step portion, the sensitivity of the semiconductor acceleration sensor can be controlled by adjusting the movable range of the weight portion. .

According to the third aspect of the present invention, since the projections are a plurality of columnar projections, the projections can be easily formed, and the position of the projections can be changed and finely adjusted. .

According to the fourth aspect of the present invention, since the projection is a linear projection formed in parallel with the side of the swinging tip of the weight, the movable range of the weight is adjusted. In addition, the sensitivity of the semiconductor acceleration sensor can be controlled, and an air damping effect can be provided.

According to the fifth aspect of the present invention, since the linear projection is formed on the swinging tip of the weight, the sensitivity of the semiconductor acceleration sensor is controlled by adjusting the movable range of the weight. And an air damping effect can be provided, and furthermore, the inertia of the weight portion is increased and the sensitivity is improved.

According to the sixth aspect of the present invention, since the concave portion is formed on the step forming surface or the opposite surface of the weight portion,
An effect that an air damping effect can be provided is achieved.

According to the seventh aspect of the present invention, since the notch is formed in the side wall of the concave portion, there is an effect that the air damping effect can be finely adjusted.

[Brief description of the drawings]

FIG. 1 is a perspective view of a weight portion of a semiconductor acceleration sensor according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a weight portion of the semiconductor acceleration sensor according to the first embodiment of the present invention.

FIG. 3 is a perspective view of a weight portion of the semiconductor acceleration sensor according to the first embodiment of the present invention.

FIG. 4 is a perspective view of a weight portion of the semiconductor acceleration sensor according to the first embodiment of the present invention.

FIG. 5 is a perspective view of a weight portion of the semiconductor acceleration sensor according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a manufacturing process according to the first to fourth embodiments of the present invention.

FIG. 7 is a diagram showing a manufacturing process (first manufacturing process) according to the first embodiment of the present invention.

FIG. 8 is a diagram illustrating a manufacturing process (second manufacturing process) according to the second embodiment of the present invention.

FIG. 9 is a diagram illustrating a manufacturing process (third manufacturing process) according to a third embodiment of the present invention.

FIG. 10 shows a manufacturing process (fourth embodiment) of the fourth embodiment of the present invention.
FIG.

FIG. 11 shows a manufacturing process (fifth embodiment) of the fifth embodiment of the present invention.
FIG.

FIG. 12 shows a manufacturing process (sixth embodiment) of the sixth embodiment of the present invention.
FIG.

FIG. 13 is a view showing a conventional semiconductor pressure sensor.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate (silicon substrate) 3 piezoresistor 4 aluminum layer 6 upper glass stopper 7 lower glass stopper 10 weight 10a step 10b columnar projection 10c linear projection 10d linear projection 10e recess 11 semiconductor substrate (frame) 12 flexure 13 penetration Hole

Continued on the front page (72) Inventor Takuro Ishida 1048 Kadoma Kadoma, Osaka Pref.Matsushita Electric Works, Ltd. (72) Inventor Masashi Kataoka 1048 Kadoma Kadoma, Kadoma, Osaka Pref. Inventor Hironori Kami 1048 Kadoma Kadoma, Kadoma, Osaka Prefecture, Japan (72) Inventor Takashi Saijo 1048 Odaka Kadoma, Kadoma, Osaka Prefecture Inside the Matsushita Electric Works, Ltd. (72) Makoto Saito, Kadoma, Osaka 1048 Oaza Kadoma Matsushita Electric Works Co., Ltd. F-term (reference) 4M112 AA02 BA01 CA23 CA36 DA03 DA04 DA06 DA10 DA11 DA14 EA03 EA06 EA07 EA11 EA13 GA01

Claims (7)

[Claims] A weight portion rotatably supported by a support portion via a flexure portion, and a piezoresistor for detecting distortion generated in the flexure portion by the flexure portion swinging. A semiconductor acceleration sensor chip having a semiconductor acceleration sensor chip that detects acceleration based on a change in the resistance value of the piezo resistor, and a stopper that is joined to the semiconductor acceleration sensor chip and that suppresses excessive displacement of the weight portion; A semiconductor acceleration sensor, wherein a step portion is formed in the weight portion to reduce the thickness in the vicinity of the swinging tip of the weight portion. 2. The semiconductor acceleration sensor according to claim 1, wherein a projection is formed on the step. 3. The semiconductor acceleration sensor according to claim 2, wherein said projection is a plurality of columnar projections. 4. The semiconductor acceleration sensor according to claim 2, wherein the protrusion is a linear protrusion formed in parallel with a side of the swinging tip of the weight. 5. The semiconductor acceleration sensor according to claim 4, wherein said linear projection is formed on a swinging tip of said weight portion. 6. The semiconductor acceleration sensor according to claim 1, wherein a recess is formed in the step forming surface or the opposite surface of the weight portion. 7. The semiconductor acceleration sensor according to claim 1, wherein a notch is formed in a side wall of the recess.