JPH10111311A - Semiconductor acceleration sensor and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor acceleration sensor and its manufacturing method reducing residual strain caused by the difference of thermal expansion coefficients between substrates to be jointed objects so as to suppress output hysteresis caused by temperature change. SOLUTION: A semiconductor acceleration sensor is provided with a detector 10 formed of a semiconductor, and a weight body 22 and support bodies 21 cut out from the same glass substrate. The detector 10 is provided with a center thick-walled part 14, thin-walled parts 13 formed around it, and peripheral thick-walled parts 15 formed around them. The weight body 22 is jointed to the lower face of the center thick-walled part 14, and the support bodies 21 are jointed to the lower faces of the peripheral thick-walled parts 15. Resistance parts 11 changed in electric resistance in response to the flexural quantity of the thin-walled parts 13 are formed at the thin-walled parts 13. A plurality of holes are respectively formed at the upper face and lower face of the support body 21 so as to reduce residual strain caused by the difference of thermal expansion coefficients between the substrates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor acceleration sensor and a method for manufacturing the same.

[0002]

2. Description of the Related Art A semiconductor acceleration sensor is known as one of detectors used for detecting the movement of an object. A conventional semiconductor acceleration sensor has, for example, a configuration as shown in FIG. This semiconductor acceleration sensor has a first
It has a three-layer structure including a silicon substrate 10 as a substrate, a glass substrate 20 as a second substrate, and a silicon substrate 30 as a third substrate. First substrate 10, second substrate 20, second substrate 2
The 0 and third substrate plates 30 are respectively bonded using an anodic bonding method. In the anodic bonding method, a member to be bonded is heated to, for example, 400 ° C. or more, and in this state, a high voltage is applied to forcibly cause ion transfer between the two members.
This is a technology that integrates these. The first substrate 10 includes a central thick portion 14, a thin portion 13 formed around the central thick portion 14, and a peripheral thick portion 1 formed around the thin portion 13.
5 and functions as a detector for detecting acceleration. In the thin portion 13, a plurality of resistance portions 11 whose electric resistance changes according to the amount of bending of the thin portion 13 are formed at predetermined positions. The weight body 22 is joined to the lower surface of the central thick portion 14. A support 21 is joined to the lower surface of the peripheral thick portion 15. Third substrate 30
Is a pedestal for restricting the movement of the weight body 22.

When a lateral acceleration as shown in FIG. 10, for example, acts on the semiconductor acceleration sensor having such a configuration, the weight body 22 is positioned at the center of the upper part of the central thick portion 14. Rotational motion is performed as a reference, and the thin portion 13 is deformed accordingly. Each resistance portion 11 embedded in the thin portion 13 has an electrical resistance value that changes according to the deformation. The acceleration sensor calculates the direction and magnitude of the acceleration by detecting the change in the electric resistance.

[0006] FIG. 11 shows an outline of a detection circuit composed of the resistance section 11.

In FIG. 1, four resistance portions 11 (resistance values: R ₁ , R ₂ , R ₃ , R ₄ ) form a bridge circuit, and the fluctuating voltage is extracted as acceleration.

[0006]

By the way, general semiconductor acceleration sensors such as the above-described semiconductor acceleration sensor usually have an inherent temperature characteristic with respect to the output of the bridge circuit. Therefore, even if the acceleration is not particularly working, if the ambient temperature changes, a voltage change corresponding thereto will occur. The change of the output voltage according to the temperature change is, for example, as shown in FIG.

However, in the conventional semiconductor acceleration sensor, as shown in FIG. 1, there is a problem that output hysteresis occurs and correction calculation is difficult.

The inventors of the present application have conducted intensive studies on this problem, and as a result, the cause of output hysteresis due to temperature change is caused by the difference in the coefficient of thermal expansion between substrates to be bonded. It was found that the residual strain was on the substrate.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor acceleration sensor in which residual strain due to a difference in the coefficient of thermal expansion between substrates to be bonded is reduced, thereby suppressing output hysteresis due to a change in temperature. It is to provide a manufacturing method.

[0010]

According to one aspect of the present invention, there is provided a semiconductor acceleration sensor, comprising: a detector made of a semiconductor; a weight and a support cut out from the same glass substrate; The detection body comprises a central thick part, a thin part formed around the central part, a peripheral thick part formed around the central part, and the weight body is provided on a lower surface of the central thick part. In the semiconductor acceleration sensor, the support is bonded to the lower surface of the peripheral thick part, and the thin part has a resistance part whose electric resistance changes according to the amount of bending of the thin part. A semiconductor acceleration sensor is provided, wherein a plurality of holes are formed on an upper surface of the support.

According to one embodiment of the present invention, there is provided a method for manufacturing a semiconductor acceleration sensor, comprising: a detection body made of a semiconductor; a weight and a support cut out from the same glass substrate. The detection body includes a central thick portion, a thin portion formed therearound, a peripheral thick portion formed therearound, and the weight body is joined to a lower surface of the central thick portion, When manufacturing a semiconductor acceleration sensor, the support is joined to the lower surface of the peripheral thick part, and the thin part is formed with a resistance part whose electric resistance changes according to the amount of deflection of the thin part. A thin film having a predetermined pattern is formed on a semiconductor substrate, and a part of the semiconductor substrate is removed by etching using the thin film as a mask, so that the central thick portion, the thin portion, and the peripheral portion are removed. Semiconductor acceleration sensor that forms a thick part In the manufacturing method, a thin film having a plurality of windows is formed in a region where the peripheral thick portion of the semiconductor substrate is formed, and simultaneously with the etching process, the thin film having the plurality of windows is used as a mask to form the peripheral thickness. A method of manufacturing a semiconductor acceleration sensor is provided, wherein a plurality of holes are formed in a flesh portion by etching.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a semiconductor acceleration sensor according to the present invention will be described below with reference to the drawings.

First, a method for manufacturing the semiconductor acceleration sensor according to the present embodiment will be described. In manufacturing the acceleration sensor, first, a silicon substrate is prepared, and on the upper surface thereof,
A silicon epitaxial layer is grown. Subsequently, for example, a silicon nitride film is formed on both sides of the substrate. The silicon nitride film on the back surface is used in an etching step (step in FIG. 1B). For the formation of the silicon nitride film, for example, LP-
A CVD technique (low pressure chemical vapor deposition technique) can be used.

Thereafter, the silicon nitride film existing on the above-mentioned epitaxial layer is peeled off to expose the epitaxial layer. For example, a silicon oxide film is grown on the exposed epitaxial layer. The silicon oxide film is subjected to predetermined patterning using photolithography, and predetermined impurities are diffused into the epitaxial layer through the patterned silicon oxide film, and a plurality of resistance portions (specifically,
Piezoresistors) are formed at predetermined positions. A metal wire connected to a piezo resistor or the like is also wired at the same time. By changing the number and arrangement of the resistance parts, it is possible to detect any one to three axes of acceleration as an acceleration sensor. On the other hand, an etching mask pattern is formed on the silicon nitride film left on the back surface of the silicon substrate by photolithography.

The silicon substrate having undergone the above steps is shown in FIG.
This is shown in FIG. Since each of the above steps is already well known, the description using the drawings is omitted, but the present invention is not limited to these steps. The above-mentioned silicon substrate is hereinafter referred to as a first substrate 1
Call it 0. Also, in FIG.
Denotes a resistance part, and 12 denotes an etching mask. The crystal plane of the first substrate (silicon substrate) 10 is (100), which is parallel to the plane A perpendicular to the plane of the drawing.

Next, etching is performed from the back surface of the first substrate 10 with a strong alkaline aqueous solution (for example, an aqueous solution of potassium hydroxide), and the etching proceeds to the back side of the epitaxial layer 16 in which the resistance portion 11 is embedded. FIG.
(B) shows a state in which the etching has been completed. The first substrate 10 has a central thick portion 14 and a peripheral thick portion 1.
5 and a thin portion 13 are formed.

Subsequently, a glass substrate (second substrate) 20 as shown in FIGS. 2 and 3 is prepared. FIG. 2 is a top view of the second substrate 20, and FIG. 3 is a bottom view of the second substrate 20.
The peripheral edge of the upper surface of the second substrate 20 is a portion to be joined to the peripheral thick portion 15, where a plurality of holes 20a are formed as shown in FIG. The peripheral edge of the lower surface of the second substrate 20 is a portion to be joined to a pedestal described later.
As shown in FIG. 5, a plurality of holes 20b are formed. The region surrounded by the plurality of holes 20b is shallowly cut off in a square shape. This part is then cut out as a weight. These holes and the shallowly shaved portion 20c at the center of the lower surface are formed simultaneously by etching.

In the etching operation, first, a metal film (for example, a chromium film) is deposited on each surface of the glass substrate,
A resist is applied thereon and is exposed to light to form a predetermined mask. Then, the metal film is etched with this mask,
A predetermined patterning is performed on the metal film. Finally, the glass substrate is etched using the metal film as a mask. For example, hydrofluoric acid can be used as the etchant.

Thereafter, the second substrate 20 is bonded to the first substrate 10 by anodic bonding. The anodic bonding is a method in which a high voltage is applied between members to be bonded and both members are pressed and bonded. After joining the second substrate 20 to the first substrate 10, the second substrate 20 is cut using a dicing blade. By the cutting, the weight body 22 and the support body 21 are formed. FIG. 1 shows how the weight body 22 and the support body 21 are formed.
It is shown in (c).

Finally, a pedestal 30 made of silicon is bonded to the back surface of the support 21. The pedestal 30 is, for example,
It may be the mounting surface of the package in which the acceleration sensor is stored. The anodic bonding method can be used for bonding the second substrate 20 and the pedestal 30 as described above.

The semiconductor acceleration sensor completed through the above steps has the configuration shown in FIG. That is, the semiconductor acceleration sensor is a detection object 1 made of a semiconductor.
0, and a weight body 22 and a support body 21 cut out from the same glass substrate.
4, a thin portion 13 formed around the periphery, a thick peripheral portion 15 formed around the thin portion 13, the weight body 22 is joined to the lower surface of the central thick portion 14, and the support 21 is Meat part 1
5, the thin portion 13 is formed with a resistance portion 11 whose electric resistance changes according to the amount of deflection of the thin portion 13. The semiconductor acceleration sensor is characterized in that a plurality of holes are formed on each of the upper surface and the lower surface of the support 21.

If a plurality of holes are formed on each of the upper surface and the lower surface of the support 21, the joint area between the support 21 and the peripheral thick portion 15 and the joint area between the support 21 and the pedestal 30 are reduced. I do.

Therefore, in the present embodiment, the effect of the residual strain due to the difference in the coefficient of thermal expansion, which usually occurs after the glass member is bonded to the silicon member, is reduced by the small bonding area. , The temperature characteristic of the output of the bridge circuit becomes linear as shown in FIG.

If such an output is obtained, the relationship between the ambient temperature and the circuit output can be grasped as a simple proportional relationship, and the correction calculation becomes very simple.

The plurality of holes formed on the upper surface and the lower surface of the support 21 are not limited to the "dents" as in this embodiment, but may be through holes.

Next, another embodiment of the present invention will be described.

In this embodiment, as shown in FIG.
A plurality of holes 15a are formed on the back surface of the substrate 10, and a plurality of holes 30a are formed on the surface of the third substrate 30 as shown in FIG.
Are formed. The plurality of holes 15a of the first substrate 10 are provided in a joint region with the upper surface of the support, and the plurality of holes 30a of the third substrate 30 are provided in a joint region with the lower surface of the support. In a region surrounded by the plurality of holes 30a, there is a portion 30b which is shaved into a square shape. This portion is a portion facing the weight body with a gap.

Even with the above configuration, the above-mentioned residual strain is reduced.

The plurality of holes 15a on the lower surface of the first substrate 10 can be formed by etching together with the central thick portion 14 and the peripheral thick portion 15.

In order to form the central thick portion 14 and the peripheral thick portion 15 by etching, as described above, a mask having openings conforming to these shapes is required.
When a plurality of holes 15a are simultaneously formed, a plurality of small rectangular windows may be provided in the mask together with the openings. At this time, the difference between the depth of the hole 15a and the depth of the polygonal groove formed between the central thick portion 14 and the peripheral thick portion 15 does not need to be particularly considered.

When etching silicon, generally,
Erosion will proceed based on the crystal structure, and specifically, the etching rate will be different for each surface. For example, since the (111) plane has a higher potential than the (100) plane, the etching rate is lower. When KOH is used as an etchant,
The etching rate of the (111) plane is 1/100 that of the (100) plane.
It may be around 40.

As a result of this action, even if etching is started simultaneously with the same mask, as shown in FIG. 8, the depths of the plurality of holes 15a and the octagonal grooves 15b are
Each will be different.

Although the two embodiments of the present invention have been described above, in each embodiment, both the joint area between the peripheral thick portion and the support and the joint area between the support and the pedestal are reduced. However, for example, even in the case where only the former (the bonding area between the peripheral thick portion and the support) is reduced, it is possible to obtain an effect corresponding thereto.

When the invention of the present application is viewed negatively, the hysteresis of the output caused by the temperature change is caused by the residual strain due to the difference in the coefficient of thermal expansion of the object to be joined. It is not impossible to think that the problem will be solved if the object is selected.

However, in the case of a semiconductor acceleration sensor, the use of a member having a similar coefficient of thermal expansion inevitably involves joining silicon substrates. In this case, the following inconvenience occurs.

In order to directly join silicon substrates, the joining temperature must be 800 ° C. or higher. However, metal lines constituting a detection circuit are often made of aluminum or the like. At high temperatures, the metal line melts.

It is also conceivable to provide a sputtered glass as a bonding layer between two silicon substrates. However, this method requires a long time for sputtering (for example, several hours per micron), There is a problem that oxygen vacancies easily occur. of course,
Annealing may be performed in an oxygen atmosphere to repair oxygen defects. However, in this case, the cost is high and it is not practical for mass production of sensors.

The present invention becomes even more significant when considering the circumstances specific to such a semiconductor acceleration sensor.

[0039]

According to the semiconductor acceleration sensor of the present invention, since the residual strain due to the difference in the coefficient of thermal expansion between the substrates to be bonded is reduced, the output hysteresis caused by the temperature change is suppressed.

[Brief description of the drawings]

FIG. 1 is an explanatory view relating to each manufacturing process of one embodiment of a semiconductor acceleration sensor according to the present invention.

FIG. 2 is a top view of a second substrate (glass substrate) used in one embodiment of the semiconductor acceleration sensor according to the present invention.

FIG. 3 is a bottom view of a second substrate (glass substrate) used in one embodiment of the semiconductor acceleration sensor according to the present invention.

FIG. 4 is a configuration diagram of an embodiment of a semiconductor acceleration sensor according to the present invention.

FIG. 5 is a bottom view of a first substrate (silicon substrate) used in another embodiment of the semiconductor acceleration sensor according to the present invention.

FIG. 6 is a top view of a third substrate (silicon substrate) used in another embodiment of the semiconductor acceleration sensor according to the present invention.

FIG. 7 is a graph showing temperature characteristics of an output of a bridge circuit provided in one embodiment of the semiconductor acceleration sensor according to the present invention.

FIG. 8 is an explanatory diagram relating to an etching rate of a first substrate (silicon substrate) used in another embodiment of the semiconductor acceleration sensor according to the present invention.

FIG. 9 is a configuration diagram of a conventional semiconductor acceleration sensor.

FIG. 10 is a diagram illustrating the operation of a conventional semiconductor acceleration sensor.

FIG. 11 is an explanatory diagram showing a basic configuration of a bridge circuit used in a general semiconductor acceleration sensor.

FIG. 12 is a graph showing an output of a bridge circuit of a conventional semiconductor acceleration sensor.

[Explanation of symbols]

 10: first substrate, 11: resistance portion, 12: etching mask, 13: thin portion, 14: central thick portion, 15: peripheral thick portion, 16: epitaxial layer, 20: second substrate, 15a, 20a, 20b, 30a: hole, 21: support, 22: weight, 30: third substrate

Claims (7)

[Claims] 1. A detection body comprising a semiconductor, a weight body and a support body cut out from the same glass substrate, wherein the detection body has a central thick portion, a thin portion formed around the central portion, and a thin portion formed around the central portion. The weight body is joined to a lower surface of the central thick portion, the support is joined to a lower surface of the peripheral thick portion, and the thin portion is A semiconductor acceleration sensor in which a resistance portion whose electric resistance changes according to the amount of deflection of the thin portion is formed, wherein a plurality of holes are formed in an upper surface of the support; Sensor. 2. The semiconductor according to claim 1, further comprising a pedestal made of a semiconductor, which is joined to a lower surface of the support, wherein a plurality of holes are formed in the lower surface of the support. Acceleration sensor. 3. The semiconductor according to claim 1, further comprising a pedestal made of a semiconductor, which is joined to a lower surface of the support, wherein a plurality of holes are formed in a joining surface of the pedestal. Acceleration sensor. 4. A detection body comprising a semiconductor, a weight body and a support body cut out of the same glass substrate, wherein the detection body has a central thick portion, a thin portion formed therearound, The weight body is joined to a lower surface of the central thick portion, the support is joined to a lower surface of the peripheral thick portion, and the thin portion is A semiconductor acceleration sensor having a resistance portion whose electric resistance changes in accordance with the amount of deflection of the thin portion, wherein a plurality of holes are formed on a lower surface of the peripheral thick portion. Semiconductor acceleration sensor. 5. The semiconductor according to claim 4, further comprising a pedestal made of a semiconductor joined to the lower surface of the support, wherein a plurality of holes are formed in the lower surface of the support. Acceleration sensor. 6. The semiconductor according to claim 4, further comprising a pedestal made of a semiconductor, which is joined to a lower surface of the support, wherein a plurality of holes are formed in a joining surface of the pedestal. Acceleration sensor. 7. A detection body comprising a semiconductor, a weight body and a support cut out from the same glass substrate, wherein the detection body has a central thick portion, a thin portion formed around the central portion, The weight body is joined to a lower surface of the central thick portion, the support is joined to a lower surface of the peripheral thick portion, and the thin portion is When manufacturing a semiconductor acceleration sensor in which a resistance part whose electric resistance changes according to the amount of deflection of the thin part is formed, a thin film having a predetermined pattern is formed on a semiconductor substrate, and the thin film is used as a mask. A method of manufacturing a semiconductor acceleration sensor that forms the central thick portion, the thin portion, and the peripheral thick portion by removing a part of the semiconductor substrate by etching. In the area where the meat part is formed,
A thin film having a plurality of windows is formed, and simultaneously with the etching process, a plurality of holes are formed in the peripheral thick portion by etching using the thin film having a plurality of windows as a mask. Production method.