JPH0536993A - Semiconductor pressure detector - Google Patents

Abstract

PURPOSE:To provide a semiconductor pressure detector where highly accurate detection output is guaranteed by lightening the thermal stress working on a strain gate at a diaphragm part in case of putting it, especially, in face down structure. CONSTITUTION:A diaphragm 12 is made on a round or square-shaped silicon wafer 11 of face orientation {100} or {110}, and a silicon oxide film 14 and a silicon film layer 15 are made, and a silicon film layer 15 is made together with a silicon oxide film 14 on the surface of this silicon wafer 11, and with this silicon wafer as a spacer, a glass pedestal 16 is junctioned. And one part of the silicon film layer 15 is removed, and a pressure standard chamber 17 is made, corresponding to the region of the diaphragm 12, and strain gauges 181-184, which constitute bridges, are arranged at the surface of the diaphragm 12. In this case, these strain gauges 181-184, defining that the distance from the center of the diaphragm 12 is (x) and that the distance between the center of the diaphragm 12 and the end is (a), are set in the region of 'x/a<=0.88'.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure detecting device having a face-down structure, in which a plurality of strain gauges connected in a bridge shape are formed in a diaphragm portion made of a silicon wafer.

[0002]

2. Description of the Related Art For example, Japanese Laid-Open Patent Publication No. 2-138767 discloses a pressure detecting device having a face-down structure in which a surface of a silicon chip on which a strain gauge is arranged and a glass pedestal are joined.

In this face-down structure semiconductor pressure detecting device, a silicon oxide film (SiO ₂ ) is formed on the surface of a silicon chip forming a diaphragm, and anodically bonding is performed on the silicon oxide film. A silicon thin film made of polycrystalline silicon is deposited, and the silicon thin film is removed by etching to form a pressure reference chamber on a portion of the silicon thin film corresponding to the diaphragm. Then, the glass pedestal is joined using this silicon thin film as a spacer.

In the pressure detecting device having such a structure, the silicon wafer, the silicon oxide film, and the silicon thin film have different thermal expansion coefficients. Therefore, thermal stress is generated on the surface of the diaphragm on which the strain gauge is arranged.

This thermal stress causes temperature dependence of the offset voltage as the pressure detecting device, and particularly causes deterioration of the measurement accuracy of the pressure detecting device installed in a portion where a large amount of heat acts.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and particularly in the case of a face-down structure in which a glass pedestal is bonded to the surface of a silicon wafer using a silicon thin film as a spacer, An object of the present invention is to provide a semiconductor pressure detecting device in which the influence of thermal stress on the measurement accuracy is eliminated and the reliability of the detection accuracy is improved.

[0007]

In a semiconductor pressure detecting device having such a structure, a semiconductor wafer having a crystal plane orientation of {100} round, or {110} round or square silicon wafer is formed. In a pressure detecting device in which a pedestal is joined using a silicon thin film as a spacer, and a plurality of strain gauges forming a bridge circuit are arranged on a diaphragm formed on the silicon wafer, a distance between a center of the diaphragm and the strain gauge is x, and the diaphragm is When the distance between the center and the end of the is set to a, “x / a ≦ 0/88” is set.

[0008]

By arranging the strain gauges in this way, the thermal stress applied to each strain gauge is canceled due to the difference in the coefficient of thermal expansion of the silicon wafer, the silicon thin film, etc., and the Wheatstone bridge constructed by the strain gage is constructed. It is possible to suppress the output due to the thermal stress from. Therefore, the detection accuracy of this pressure detection device is effectively improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the structure of a semiconductor pressure detecting device, in which a diaphragm 12 is formed by removing a silicon wafer 11 having a crystal orientation of {100} or {110} by etching. The pressure medium to be measured acts on the portion of the chamber 13 corresponding to the diaphragm 12.

A silicon oxide film layer 14 is formed on the entire surface of the silicon wafer 11, and the silicon oxide film layer 14 is formed.
14 thin film layer made of polycrystalline silicon
15 are deposited. Then, the glass pedestal 16 is bonded using the silicon thin film layer 15 as a spacer.

In this case, the portion of the silicon thin film layer 15 corresponding to the diaphragm 12 is removed by etching so that a pressure reference chamber 17 in a vacuum state is formed between the diaphragm 12 and the glass pedestal 16. I have to.

This pressure detecting device has a face-down structure in which a silicon wafer 11 having a diaphragm 12 formed through a silicon thin film 15 and a glass pedestal 16 are bonded to each other. A plurality of strains are formed on the surface of the diaphragm 12. Gauge 181
, 182, ... Are formed. And these strain gauges 181
, 182, ... Are connected to the Wheatstone bridge by aluminum wiring 19 or the like.

2 (A) to 2 (C) constitute a Wheatstone bridge for the diaphragm 12, respectively.
It shows the arrangement of the individual strain gauges 181-184,
(A) and (B) show a case where the diaphragm 12 is formed in a circular shape, and (C) shows a case where the diaphragm 12 is formed in a square shape.

In order to eliminate the influence of thermal stress in the silicon semiconductor pressure detecting device which constitutes the Wheatstone bridge by the four strain gauges 181 to 184, in order to eliminate the influence of thermal stress, the silicon plane orientation is {110} in (A) and (C). In the case of the figure, since only the longitudinal thermal stress ρ _L contributes to the resistance change of the strain gauge, the two strain gauges 183, 184 arranged at the center of the diaphragm and the other two strain gauges 181. , 182 may be set so that the thermal stresses Δ _{L in} the vertical direction are equal. Moreover, as shown in FIG.
In this case, the longitudinal thermal stress σ _L and the lateral thermal stress σ _T applied to the four strain gauges 181 to 184 may be equal to each other.

FIG. 3 shows a silicon chip having a face-down structure in which a glass pedestal 16 is bonded using a silicon thin film layer 15 deposited on the surface of a silicon chip (silicon wafer 11) obtained by a finite element method (FEM) as a spacer. An example of the distribution of thermal stress on the surface (the surface on which the strain gauges 181 to 184 are arranged) is shown. (A) shows the case of a round diaphragm, (B) shows the case of a square diaphragm. ..

This thermal stress varies depending on the thickness and diameter of the diaphragm, the film thicknesses of the silicon oxide film layer 14 and the silicon thin film layer 15 deposited on the silicon chip, the formation temperature of these films, and the like. The shape does not change with these conditions (confirmed by FEM). Therefore, in such a face-down structure pressure detection device, the situation shown in FIG. 3 is generally established.

Therefore, by limiting the shape of the silicon diaphragm 12 and the positions where the strain gauges 181 to 184 are arranged as follows, it is possible to construct a highly accurate pressure detecting device which is not affected by thermal stress. it can.

A) Silicon plane orientation {100} or {1
10} round diaphragm, “x / a = 0.
Strain gauges are arranged in the following regions of 88 ″. B) In a square diaphragm having a silicon plane orientation of {110}, strain gauges are arranged in the regions of “x / a = 0.88 or less.

However, x: distance from the center of the diaphragm of the strain gauge. a: Distance between the center and the end of the diaphragm (the radius of the round shape).

FIG. 4 shows a general pressure detecting device constructed by joining a rear surface of the silicon wafer 11 on which the measured pressure corresponding to the diaphragm 12 is formed and the glass pedestal 16 to each other. A silicon oxide film layer 14 is formed on the surface of the silicon wafer 11. Then, the glass pedestal 16 is connected to the chamber 13 so as to communicate with the pressure introducing hole 20.
Are formed.

Also in the pressure detecting device having such a structure,
Although thermal stress is generated by the silicon oxide film layer 14 and the like, in the entire surface of the silicon wafer 11, the longitudinal and lateral thermal stresses are equal and their values are constant, so Output due to thermal stress from the Wheatstone bridge does not occur regardless of the position of the gauges 181-184.

[0022]

As described above, according to the semiconductor pressure detecting device of the present invention, particularly in the face-down structure, the silicon surface orientation is the round shape of {100} or the surface orientation of {11}.
The position of the strain gauge arranged on the diaphragm formed on the round or square silicon wafer of 0} is represented by "x /
By setting a ≦ 0.88 ″, for example, the thermal stresses applied to the plurality of strain gauges forming the bridge circuit can be canceled each other, and the output due to the thermal stress is suppressed as the Wheatstone bridge. , The pressure detection accuracy is improved, and the reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram illustrating a semiconductor pressure detection device according to an embodiment of the present invention.

FIGS. 2A to 2C are diagrams showing examples of arrangement states of strain gauges of the pressure detection device.

3 (A) and 3 (B) are views for explaining a distribution state of thermal stress obtained by a finite element method in a round type diaphragm and each type diaphragm, respectively.

FIG. 4 is a diagram illustrating a general configuration of a pressure detection device.

[Explanation of symbols]

11 ... Silicon wafer, 12 ... Diaphragm, 13 ... Room, 14
… Silicon oxide film layer, 15… Silicon thin film, 16… Glass pedestal, 17… Pressure reference chamber, 181-184… Strain gauge.

Claims (1)

[Claims] 1. A round shape having a silicon surface orientation of {100} or a diaphragm having a diaphragm formed in communication with a pressure chamber to be measured.
10} round or square silicon wafer, a silicon thin film deposited and formed on the surface of the silicon wafer except for the diaphragm formation portion, and the silicon wafer is bonded using the silicon thin film as a spacer to form the diaphragm. A pedestal that forms a pressure reference chamber in a portion corresponding to, and a plurality of strain gauges formed corresponding to the diaphragm portion of the silicon wafer, and a distance between the strain gauge and the center of the diaphragm is x. ,
And the distance between the center of the diaphragm and its end is a
In this case, the semiconductor pressure detecting device is characterized in that "x / a≤0.88" is set.