JPH07202221A - Semiconductor acceleration sensor - Google Patents

Abstract

PURPOSE:To improve sensitivity in detecting acceleration, by forming an outward projected part at a position that crosses a hypothetical line of an inner circumferential part in a diaphragm part. CONSTITUTION:Resistance elements Rx1, Rx4, Ry1, and Ry4 are formed in contact with an outer circumferential edge part 43c of a diaphragm 43, while resistance elements Rx2, Rx3, Ry2, and Ry3 are formed in contact with a corner part 43b. When acceleration is applied to the weight in an X-direction, the force caused by the acceleration is applied to the diaphragm 43. In this case, larger stress is caused along a diagonal line, on which the resistance elements are formed, and its vicinities than the other part of the diaphragm 43, because the corner part 43b of an inner circumferential edge part 43a and a side part 43d of the outer circumferential edge part 43c are provided opposite. Then, the resistance element is deformed greatly, and thereby an acceleration sensor 1A can be improve in detection sensitivity.

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 the magnitude of acceleration.

[0002]

2. Description of the Related Art A conventional acceleration sensor of this type is disclosed in Japanese Patent Application Laid-Open Nos. 63-266325 and 4-84725. 22 (A) and 22 (B) show an example of such a conventional acceleration sensor 1. The acceleration sensor 1 includes a base 2 and a rectangular frame fixed to the upper surface of the base 2. It is composed of a pedestal 3 having a shape and a substrate 4 made of single crystal silicon fixed to the upper surface of the pedestal 3. An annular concave portion 41 is formed on the lower surface of the substrate 4, and the concave portion 41 causes the substrate 4 to have a central action portion 42, a thin diaphragm portion 43 located above the concave portion 41, and a concave portion 41. It is divided into three parts with the support part 44 located outside.

The supporting portion 44 is fixed to the upper surface of the pedestal 3 by adhesion, anodic bonding or the like, whereby the substrate 4 is fixed to the pedestal 3. The weight 5 is integrally formed on the lower surface of the action portion 42, or is fixed by adhesion or anodic bonding.

A plurality of resistance elements are formed on the upper surface of the diaphragm portion 43. That is, two virtual straight lines (X axis, Y
Aligns with the axis. ) And each of the straight lines passing through the intersections of the two straight lines and a virtual straight line forming a small angle with one straight line, four resistance elements R _{1 to} R ₄ (Rx ₁ to
Rx ₄ ; Ry _{1 to} Ry ₄ ; Rz _{1 to} Rz ₄ ) are formed. Two resistance elements R out of the _four resistance elements R _{1 to} R _4
1 and R ₂ are arranged on the outer side and the inner side on one side with the acting portion 42 therebetween, and the other two resistance elements R ₃ and R ₄ are arranged on the inner side and the outer side on the other side, respectively. ing. Moreover, the resistance elements R ₁ and R ₂ and the resistance elements R ₃ and R ₄ are arranged symmetrically.

[0005] X with a semiconductor acceleration sensor 1 of the above structure, Y, in the case of detecting the acceleration acting on the axial direction of Z, said resistive element _{Rx n, Ry n, Rz n} (n = 1~
4) is incorporated into the bridge circuits C ₁ , C ₂ and C ₃ shown in FIGS. 23A, 23B and 23C, respectively. When the acceleration in the X-axis direction acts on the weight 5, the voltage Vx generated in accordance with the magnitude of the acceleration in the bridge circuit C _1, the other bridge circuit C _2, the voltage of C ₃ Vy, Vz is zero Become. The same applies when accelerations in the other axial directions act, and voltages Vy and Vz corresponding to the accelerations in the Y-axis and Z-axis directions are generated, and the other voltages become zero.

The voltages Vx, Vy, Vz are obtained by the following equations. In the following equation, the symbol I is the current flowing in the circuit. Vx = I (Rx ₁ Rx ₃ −Rx ₂ Rx ₄ ) / (Rx ₁ + Rx ₂
+ Rx ₃ + Rx ₄ ) Vy = I (Ry ₁ Ry ₃ −Ry ₂ Ry ₄ ) / (Ry ₁ + Ry ₂
+ Ry ₃ + Ry ₄ ) Vz = I (Rz ₁ Rz ₄ −Rz ₂ Rz ₃ ) / (Rz ₁ + Rz ₂
+ Rz ₃ + Rz ₄ )

[0007]

The above-mentioned conventional acceleration sensor 1 has a problem that it is difficult to meet the demand for improving the detection sensitivity. That is,
As a method of improving the detection sensitivity, for example, the thickness of the diaphragm portion is reduced or the outer diameter thereof is increased so that the diaphragm portion can be deformed with a small acceleration. Alternatively, a method of enlarging the weight 5 to make it heavy can be considered. However, reducing the thickness of the diaphragm portion 43 has a certain limit in terms of accuracy and strength, and thus there is a certain limitation in improving the detection sensitivity. Further, if the outer diameter of the diaphragm portion 43 is increased or the weight 5 is increased, the size of the sensor 1 as a whole is increased. Therefore, it cannot be a fundamental solution.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. An action portion is formed in the central portion, and a deformable annular diaphragm portion is provided outside the action portion. The diaphragm portion includes a substrate on which a support portion is formed outside the diaphragm portion, and a weight provided on the acting portion. The diaphragm portion has a plurality of resistance elements passing through substantially the center of the acting portion. In a semiconductor acceleration sensor arranged along an imaginary straight line and on each of an inner side portion and an outer side portion on one side and the other side with the acting portion therebetween, the imaginary portion of the inner peripheral edge of the diaphragm portion is It is characterized in that a corner portion protruding outward is formed at a portion intersecting with a straight line.

In this case, it is desirable to form a side portion orthogonal to the virtual straight line at a portion of the outer peripheral edge of the diaphragm portion that intersects the virtual straight line for a reason described later.
Further, it is desirable that a short side portion orthogonal to the virtual straight line is formed at the corner portion. Further, it is desirable that the virtual straight line substantially coincides with the direction in which the large piezoresistive coefficient appears in the diaphragm portion.

[0010]

When the acceleration acts on the weight, the diaphragm portion is deformed by the force based on the acceleration. in this case,
The stress is more concentrated in the portion of the diaphragm portion where the corner is formed than in the other portion, causing a large strain. Therefore, a large resistance value change can be obtained. Therefore, the detection sensitivity to acceleration is improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.
This will be described with reference to FIG. The examples described below are
The shapes of the inner peripheral edge and the outer peripheral edge of the diaphragm portion 43 and the arrangement of the resistance element R _n are different from the above-described conventional example, and the other configurations are the same as those of the above-described conventional example. Therefore,
Here, only different points will be described, and similar portions will be denoted by the same reference numerals and description thereof will be omitted.

In the acceleration sensor 1A shown in FIG. 1, the diaphragm portion 43 is formed on the (110) plane of the single crystal silicon substrate 4, and the upper side in the figure is the <110> direction. In this sensor 1A, the inner peripheral edge 43a of the diaphragm portion 43 is formed in a square shape whose center coincides with the center of the acting portion 42. Moreover, the inner peripheral edge 43
The square forming a has four corners 43b of <110>.
It is arranged in a direction forming an angle of approximately 45 ° with the direction.

On the other hand, the outer peripheral edge 43c of the diaphragm portion 43
Is formed into a regular octagon with its center coinciding with the center of the action portion 42. The regular octagon forming the outer peripheral edge 43c is arranged so that two pairs of side portions 43d among the four pairs of opposing side portions are orthogonal to the diagonal line of the inner peripheral edge 43a at the center thereof.

The diaphragm portion 43 has resistance elements Rx _{1 to} Rx for detecting acceleration acting in the X-axis direction.
Resistor elements Ry _{1 to} R ₄ for detecting x ₄ and acceleration acting in the Y-axis direction are formed. Resistance element Rx
_{1 to} Rx ₄ are two diagonal lines (virtual straight lines) of the inner peripheral edge 43a
Formed on an extension of one of the resistance elements Ry _{1 to} Ry
y ₄ is located on the extension of the other diagonal. Of course, the resistance elements Rx ₁ , Rx ₄ , Ry ₁ , and Ry ₄ are arranged outside the diaphragm portion 43, and the resistance elements Rx ₂ and Rx ₂
x ₃ , Ry ₂ and Ry ₃ are arranged inside the diaphragm portion 43. In particular, in this embodiment, the resistance elements Rx ₁ , Rx ₄ , Ry ₁ and Ry ₄ are arranged so as to be in contact with the outer peripheral edge 43 c of the diaphragm portion 43, and the resistance element R
x ₂ , Rx ₃ , Ry ₂ and Ry ₃ are arranged so as to be in contact with the corner portion 43b. Of course, they may be arranged separately.

In the acceleration sensor 1A having the above structure, when acceleration in the X-axis direction acts on the weight 5 (see FIG. 22B), a force based on the acceleration acts on the diaphragm portion 43. At this time, since the corner portion 43b of the inner peripheral edge 43a and the side portion 43d of the outer peripheral edge 43c face each other, the resistance element R
A larger stress acts on the diagonal line where x is arranged and in the vicinity thereof than in other portions, and the resistance element Rx is largely deformed. Therefore, the detection sensitivity of the acceleration sensor 1A can be improved. This point is the same when the acceleration in the Y-axis direction acts.

Particularly, in the acceleration sensor 1A of this embodiment, the resistance elements Rx and Ry are arranged at 45 ° with respect to the <110> direction.
Since they are arranged on a diagonal line that forms, the detection sensitivity can be further improved.

That is, as shown in FIG. 2, (110)
On the surface, the piezoresistive coefficient increases from the <110> direction to the <001> direction in the range of approximately 45 °, and particularly has a peak in the direction of approximately 45 °. Then, in the acceleration sensor 1A, the resistance elements Rx and Ry are arranged on a diagonal line that faces the direction of 45 ° with respect to the <110> direction. Therefore, the detection sensitivity can be further improved.

Next, the diaphragm portion 43 is formed on the (110) plane.
Another embodiment in which the above is formed, that is, a modification of the acceleration sensor 1A will be described. It is needless to say that the above effects of the acceleration sensor 1A can be obtained also in the following modified examples.

In the acceleration sensor 1B shown in FIG. 4, the inner peripheral edge 43a of the diaphragm portion 43 is hexagonal.
Resistor elements Rx and Ry are arranged on the extension of a diagonal line forming an angle of 45 ° with the <110> direction. The other remaining diagonal lines are oriented in the <110> direction, and resistance elements Rz _{1 to} Rz ₄ for detecting acceleration acting in the Z-axis direction are arranged on the extension of the diagonal lines. The resistance element R
Regarding z, it may be in contact with the outer peripheral edge 43c or the inner peripheral edge 43a, or may be separated therefrom.

In this acceleration sensor 1B, since the resistance element Rz is arranged between the corner portion 43b and the side portion 43d, the detection sensitivity for the acceleration in the Z axis direction is the same as the detection sensitivity in the X axis and Y axis directions. It can be improved as well. Moreover, since the resistance element Rz is arranged on the extension of the diagonal line that faces the <110> direction and the piezoresistance coefficient in that direction is large, the detection sensitivity can be further improved.

In the acceleration sensor 1C shown in FIG. 5, the inner peripheral edge 43a of the diaphragm portion 43 is formed into a regular octagon, and the resistance elements Rx and Ry are arranged on an extension of a diagonal line forming 45 ° with the <110> direction. ing. Of the remaining two diagonal lines, the resistance element Rz is arranged on the extension of the diagonal line that faces the <110> direction.

In the acceleration sensor 1D shown in FIG. 6, the resistance element Rz is arranged on a virtual straight line that makes a slight angle with the diagonal line where the resistance element Ry is arranged and that passes through the center of the acting portion. Of course, the resistance element Rz may be arranged on a virtual straight line that makes a slight angle with the diagonal line where the resistance element Rx is arranged. The angle formed by the virtual straight line on which the resistance element Rz is arranged and the diagonal line on which the resistance element Ry (Rx) is arranged is usually set to about 8 ° to 18 °.

The acceleration sensor 1E shown in FIG. 7 is a modification of the acceleration sensor 1D. In this acceleration sensor 1E, of the octagonal side portions forming the outer peripheral edge 43c,
The side portion 43d facing the resistance elements Rx and Ry is longer than the other side portions.

The acceleration sensor 1F shown in FIG.
The short side part 43e is formed in the corner part 43b of 3a. The short side portion 43e is formed so as to be orthogonal to the diagonal line in the central portion. Further, the length thereof is made longer than the width of the resistance elements Rx and Ry,
It is set to 0.3 mm.

In this acceleration sensor 1F, the corner portion 4
Stress concentration is alleviated by the amount that the short side portion 43e is formed in 3b. Therefore, the detection sensitivity is slightly lowered, but on the contrary, even if the position accuracy of the resistance elements Rx, Ry, Rz, especially the position accuracy in the direction orthogonal to the virtual straight line (diagonal line) is decreased, the detection sensitivity is also decreased. Can be prevented. Therefore, when a large number of acceleration sensors 1F are manufactured, it is possible to suppress variations in detection sensitivity between the sensors.

The acceleration sensor 1G shown in FIG. 9 uses the outer peripheral edge 43c shown in FIG. 7 instead of the outer peripheral edge 43c of the acceleration sensor 1F shown in FIG.

Next, the diaphragm portion 43 is attached to the substrate 4 (1
An example in the case of forming on the (00) plane will be described. In the acceleration sensor 1H shown in FIG. 10, the inner peripheral edge 43a
One of the two diagonal lines of is directed in the <110> direction, and the other diagonal line of the other is directed in a direction orthogonal to the <110> direction. Further, the central portion of each side of the square forming the inner peripheral edge 43a is recessed inward. As a result, the corner portion 43
b is an acute angle. On the other hand, the outer peripheral edge 43c has a square shape, and is out of phase with the square forming the inner peripheral edge 43a by 45 °.

In this acceleration sensor 1H, since the corner portion 43b of the inner peripheral edge 43a has an acute angle, the degree of stress concentration is large. Therefore, the detection sensitivity can be further improved. In addition, the resistance elements Rx and Ry are <1
10> is arranged on an extension of a diagonal line facing the direction, and the resistance element Rz is arranged on a virtual straight line facing a direction forming a slight angle with the diagonal line. Then, as shown in FIG. 3, the magnitude of the piezoresistance coefficient has a peak in the <110> direction. Therefore, the detection sensitivity can be further improved.

The acceleration sensor 1I shown in FIG. 11 has a regular octagonal outer peripheral edge 43c.

The acceleration sensor 1J shown in FIG. 12 has an octagonal resistance element Rx, Ry,
The four side portions 43d facing Rz are made longer than the other four side portions.

Acceleration sensors 1K, 1L and 1M shown in FIGS. 13, 14 and 15 respectively correspond to FIGS.
1 is a modification of the acceleration sensors 1H, 1I, 1J shown in FIG. 12, in which a short side portion 43e orthogonal to the diagonal line of the inner peripheral edge 43a and the central portion is formed in the corner portion 43b of the inner peripheral edge 43a. The length of the short side portion 43e is (1) as described above.
The length is set to be about the same as the short side portion 43e of the embodiment in which the diaphragm portion 43 is formed on the 10) surface.

Acceleration sensors 1N, 1O and 1P shown in FIGS. 16, 17 and 18 respectively correspond to FIGS.
Instead of the inner peripheral edge 43a of the acceleration sensors 1H, 1I, 1J shown in 2, the inner peripheral edge 43a is square.

The acceleration sensors 1Q, 1R and 1S shown in FIGS. 19, 20 and 21, respectively, are shown in FIGS.
In the acceleration sensors 1N, 1O, 1P shown in FIG. 8, short side portions 43e are formed at the corner portions 43b of the inner peripheral edge 43a.

The present invention is not limited to the above embodiments, but can be modified as appropriate without departing from the spirit of the invention. For example, in the above example,
Although the acceleration in the biaxial or triaxial directions is detected, the present invention can be applied to a sensor for detecting acceleration in the uniaxial directions. Further, the resistance element Rz for detecting acceleration in the Z-axis direction may be arranged in parallel with the resistance element Rx or Rz for detecting acceleration in the X-axis or Y-axis direction.

Further, one resistance element Rx (Ry, Rz) is formed in each of the inner portion and the outer portion of the diaphragm portion 43, but a plurality of resistance elements Rx (Ry, Rz) are arranged adjacent to each other in the direction orthogonal to the virtual straight line. You may form. In this case, one of the plurality of resistance elements arranged in the same portion may be arranged on the virtual straight line and the other resistance elements may be arranged along the virtual straight line, or all the resistance elements may be arranged virtually. You may arrange along a straight line.

[0036]

As described above, according to the semiconductor acceleration sensor of the present invention, the corner portion projecting outward is formed at the portion of the inner peripheral edge of the diaphragm portion that intersects with the virtual straight line. It is possible to obtain the effect that the acceleration detection sensitivity can be improved without increasing the size of the acceleration sensor.

[Brief description of drawings]

FIG. 1 is a plan view of an acceleration sensor 1A according to the present invention.

FIG. 2 shows the diaphragm portion of (11
It is a figure which shows the distribution of the magnitude | size of a piezo resistance coefficient when formed in the (0) surface.

FIG. 3 shows a diaphragm portion (10
It is a figure which shows the distribution of the magnitude | size of a piezo resistance coefficient when formed in the (0) surface.

FIG. 4 is a plan view of an acceleration sensor 1B according to the present invention.

FIG. 5 is a plan view of an acceleration sensor 1C according to the present invention.

FIG. 6 is a plan view of an acceleration sensor 1D according to the present invention.

FIG. 7 is a plan view of an acceleration sensor 1E according to the present invention.

FIG. 8 is a plan view of an acceleration sensor 1F according to the present invention.

FIG. 9 is a plan view of an acceleration sensor 1G according to the present invention.

FIG. 10 is a plan view of an acceleration sensor 1H according to the present invention.

FIG. 11 is a plan view of an acceleration sensor 1I according to the present invention.

FIG. 12 is a plan view of an acceleration sensor 1J according to the present invention.

FIG. 13 is a plan view of an acceleration sensor 1K according to the present invention.

FIG. 14 is a plan view of an acceleration sensor 1L according to the present invention.

FIG. 15 is a plan view of an acceleration sensor 1M according to the present invention.

FIG. 16 is a plan view of an acceleration sensor 1N according to the present invention.

FIG. 17 is a plan view of an acceleration sensor 1O according to the present invention.

FIG. 18 is a plan view of an acceleration sensor 1P according to the present invention.

FIG. 19 is a plan view of an acceleration sensor 1Q according to the present invention.

FIG. 20 is a plan view of an acceleration sensor 1R according to the present invention.

FIG. 21 is a plan view of the acceleration sensor 1S according to the present invention.

22 shows an example of a conventional acceleration sensor, FIG. 22 (A) is a plan view thereof, and FIG. 22 (B) is FIG. 22 (A).
FIG.

FIG. 23 shows a bridge circuit in which a resistance element of an acceleration sensor is incorporated, and FIGS. 23 (A), (B), and (C)
Is a bridge circuit for detecting acceleration acting in the X-axis, Y-axis, and Z-axis directions, respectively.

[Explanation of symbols]

 1A acceleration sensor 1B acceleration sensor 1C acceleration sensor 1D acceleration sensor 1E acceleration sensor 1F acceleration sensor 1G acceleration sensor 1H acceleration sensor 1I acceleration sensor 1J acceleration sensor 1K acceleration sensor 1L acceleration sensor 1M acceleration sensor 1N acceleration sensor 1O acceleration sensor 1P acceleration sensor Sensor 1R Acceleration sensor 1S Acceleration sensor 4 Substrate 5 Weight 42 Action part 43 Diaphragm part 43a Inner peripheral edge 43b Corner part 43c Outer peripheral edge 43d Side part 43e Short side part 44 Support part

Claims (4)

[Claims] 1. A substrate having a central portion formed with a working portion, a deformable annular diaphragm portion formed outside the working portion, and a support portion formed outside the diaphragm portion, and the working portion. A plurality of resistance elements are provided in the diaphragm portion along a virtual straight line passing through substantially the center of the action portion, and one side and the other side with the action portion interposed therebetween. In the semiconductor acceleration sensor arranged in each of the inner part and the outer part, a corner portion protruding outward is formed at a portion of the inner peripheral edge of the diaphragm portion that intersects with the virtual straight line. Semiconductor acceleration sensor. 2. The semiconductor acceleration sensor according to claim 1, wherein a side portion orthogonal to the virtual line is formed at a portion of the outer peripheral edge of the diaphragm portion that intersects the virtual line. 3. The semiconductor acceleration sensor according to claim 1, wherein a short side portion orthogonal to the virtual straight line is formed at the corner portion. 4. The semiconductor acceleration sensor according to claim 1, wherein the virtual straight line is substantially aligned with a direction in which a large piezoresistive coefficient appears in the diaphragm portion.