JP3120050B2 - Semiconductor acceleration sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device including a semiconductor acceleration sensor for converting a displacement into an electric signal by utilizing a piezoresistance effect of a semiconductor crystal such as silicon.

[0002]

2. Description of the Related Art FIG. 2 is a view showing a semiconductor acceleration sensor by micromachining disclosed in Japanese Patent Application Laid-Open No. 1-302167. 50 are provided. A diffusion resistor 2 is provided on the upper surface of the sensor, and forms a bridge circuit.

[0003]

In a conventional semiconductor acceleration sensor, as shown in FIG. 2, a bridge circuit is formed on a surface of a set of diffusion resistors 2 for detecting acceleration.
This acceleration sensor utilizes a piezoresistive effect and utilizes a phenomenon in which specific resistance changes due to stress. Here, the specific resistance change rate of the crystal can be expressed by the following equation.

△ R / R = πε π is a piezoresistance coefficient, and ε is a stress tensor component. Increasing the specific resistance change rate means improving the sensitivity. The crystal direction and the piezoresistance coefficient are shown.

[0005]

[Table 1]

As can be seen from Table 1, in the case of the P type, <11
1> and N-type take a large value at <100>. In the conventional sensor element 1, the portion having the diffusion resistance 2 is thinned to improve the sensitivity, so that the thin film has a different expansion coefficient. There was an offset drift effect due to the bimetal effect. The present invention provides a structure that is not affected by temperature.

[0007]

In order to solve the above problems, a pattern is formed on a semiconductor wafer 10 by a normal semiconductor process such as a diffusion resistor 2 and an output terminal 4.
Here, the diffusion resistor 2 is connected by a bridge circuit in which both p-type and n-type coexist. The pattern formation cuts the device into dice. Here, a dicing method was used. The surface of the element having the diffused resistance 2 is mounted on the support so as to be orthogonal to the acceleration detection surface. This was performed by a method of forming a weight at the tip of the element having a cantilever structure. As the diffusion resistance 2, two P-types and two N-types were used. The value of the piezoresistive coefficient of a semiconductor such as silicon is much larger than that of a metal material and shows a remarkable anisotropy. In p-type silicon, the specific resistance increases under tensile stress, and decreases under compressive stress. The opposite is true for n-type silicon. In the present invention, sensitivity is achieved by disposing one set of P-type diffused resistors and one set of N-type diffused resistors near the applied acceleration direction.

The specific contents will be described with reference to FIG. The P-type 101 and the N-type 102 illustrated from the applied acceleration 200 are:
Subject to tensile stress. When the P-type 101 is arranged in the crystal direction 110, a strain resistance coefficient of 71.8 can be used. N type 102 is -31.2. The sensitivity is increased by using this combination. According to this configuration, all four diffused resistors forming the bridge can be installed in the vicinity, and can be separated from the support portion. It is possible to provide a highly sensitive acceleration sensor which is less affected by temperature.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be specifically described with reference to FIG. FIG. 1A is a top view of the acceleration sensor of the present invention, FIG. 1B is a front view, and FIG. 1C is a side view. The semiconductor acceleration sensor is a rectangular parallelepiped structure formed with a diffusion resistor 2 and an output terminal 4 cut out from a semiconductor wafer 10, and this structure is hereinafter referred to as a sensor element 1. A diffused resistor 2 and an output terminal 4 are formed in a pattern on a side surface 100 of the sensor element 1, and the diffused resistor 2 and the output terminal 4 are provided on one or both sides. In the present invention, P-type and N-type diffusion resistors 2 are used as the diffusion resistors 2. A locos process was used to form the diffusion resistance. In the present invention, the arrangement of the diffusion resistor 2 is as follows.
The acceleration direction was P-type, and the downward direction was N-type. The output terminal 4 is formed with a bump for extracting an electric signal.
Here, the gold bump 3 was formed. The length of the sensor element 1 is 6 mm (L1 = 4 mm, L2 = 2 m
m), the width w was 0.6 mm, and the thickness was 0.12. The size of the bump of the output terminal 4 is 0.1 × 0.08 mm,
The height is 0.1 mm. The arrangement of the diffusion resistor 2 will be described. The size of the diffusion resistor 2 is length 0.25 mm × 0.0
The P-type diffusion resistance was 1 mm, and the P-type diffusion resistance was disposed at a distance of 10 μm from the inside of the tongue in the acceleration direction.

The main components of the semiconductor acceleration sensor are a sensor element 1, a pedestal 11 for extracting an electric signal from the sensor element 1, supporting the sensor element 1, a weight for obtaining sensitivity, and a package 30. . The detection principle is
In this method, the diffused resistor 2 on the side surface 100 bends the sensor element 1 by the applied acceleration, and the diffused resistor 2 disposed on the side surface changes its resistance value to detect acceleration. In the present invention, a configuration of a full bridge circuit in which four diffusion resistors 2 change is used.

The manufacturing method will be described with reference to FIGS.
First, as shown in FIG.
The diffusion resistor 2 and the output terminal 4 are patterned. At this time,
The semiconductor wafer 10 was (100), and patterns were arranged in the <110> direction. Also, a scribe line for cutting out is formed. Further, a gold bump is formed on the output terminal 4 portion. The steps so far are performed on both surfaces of the semiconductor wafer 10. Note that an amplifier circuit, a temperature compensation circuit, and the like may be formed during the pattern formation, as shown in FIG. 4A.

Next, the device is taken out by a dicing device with reference to the scribe line. Since the bumps are formed on the element, it is difficult to fix the element to the stage of the dicing apparatus. However, in this embodiment, the fixing is performed by using wax. Of course, a tape coated with an adhesive may be used. From the semiconductor wafer 10, the diffusion resistor 2, the output terminal 4
FIG. 4 (b) shows the sensor element 1 having the shape shown in FIG.

Next, as shown in FIG. 5A, a weight 3 for obtaining sensitivity is added to the sensor element 1. The material of the weight 3 is preferably a metal such as molybdenum. This state is set on the pedestal 11. The pedestal 11 is provided with wiring (not shown) for extracting electrical information from both side surfaces of the sensor element 1. In this embodiment, ceramic was used. The wiring was made of gold. The sensor element 1 is fixed to the base 11 with an adhesive (not shown). The electrical connection between the wiring of the pedestal 11 and the sensor element 1 uses an anisotropic conductive film in this embodiment. An anisotropic conductive film is one in which small conductive particles are dispersed in an adhesive. The particles are sandwiched between the electrodes by the thermocompression bonding so that the electrodes are electrically connected, the insulation between the adjacent electrodes is maintained, and at the same time, the mechanical bonding can be achieved by curing the adhesive. With this method,
The continuity is obtained between the bump and the output terminal 4 with conductive particles interposed. This method is a good method because no mechanical stress is applied to the sensor element 1. Of course, a method of connecting with a wire may be used (FIG. 5B).

An output result of the acceleration sensor with respect to acceleration when the P-type diffused resistor 101 and the N-type diffused resistor 102 of the present invention are used will be described. Length l is 6mm (L1 = 4m
m, L2 = 2 mm), width w is 0.6 mm, and thickness is 0.12
mm. The weight 3 was set to 60 mg at the end. The arrangement of the diffusion resistance is such that the diffusion resistance 2
Was placed. The diffused resistors were connected by a bridge circuit to form a P-type on the a-plane 110 side on the applied acceleration 200 side and an N-type immediately below the P-type. In the present invention, the length of the diffusion resistor is 250 microns, the width is 10 microns, and the distance between the P type and the N type is 10 microns. A structure having no diffusion resistance near the supporting portion on the b-side was adopted. With such a configuration, no diffusion resistance is provided near the support portion, so that a structure that is not affected by a difference in the coefficient of thermal expansion between the support portions can be obtained.
In the case of p-type diffusion, the crystal orientation is <110>
Is 71.8, and N-type is 31.8. The voltage output at this time was 5 mV, which almost satisfied the specifications.

The variation of the offset voltage depending on the temperature was 1 mV in the range of 0 to 85 degrees, and a good result was obtained. Good results, between the support,
A good result was obtained because the difference in the coefficient of thermal expansion was not received due to the absence of diffusion resistance near the support.

[0016]

According to the present invention, the diffusion resistance can be separated from the supporting portion by the configuration described above, and the following effects are obtained. By performing mechanical cutting such as dicing,
An acceleration sensor with little thermal influence can be manufactured. The sensitivity as an acceleration sensor can be improved. A device that can be easily provided at a low price can be manufactured.

[Brief description of the drawings]

FIG. 1 is a three-view drawing showing a semiconductor acceleration sensor of the present invention.

FIG. 2 is a perspective view showing a conventional semiconductor acceleration sensor of the present invention.

FIG. 3 is a perspective view showing a semiconductor acceleration sensor of the present invention.

FIG. 4 is a process chart showing a method for manufacturing a semiconductor acceleration sensor of the present invention.

FIG. 5 is a process chart showing a method for manufacturing a semiconductor acceleration sensor of the present invention.

FIG. 6 is a diagram showing an arrangement of diffusion resistors of the semiconductor acceleration sensor according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor element 2 Diffusion resistance 3 Weight 4 Output terminal 10 Semiconductor wafer 11 Pedestal 30 Package 50 Thin part 100 Side surface 101 P-type diffusion resistance 102 N-type diffusion resistance 110 a surface 111 b surface 200 Applied acceleration

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Kato 1-8 Nakase, Mihama-ku, Chiba-shi, Chiba SII RDC, Inc. (56) References JP-A-6-130083 (JP, A JP-A-1-301178 (JP, A) JP-A-5-87650 (JP, A) JP-A-5-87648 (JP, A) JP-A-8-233852 (JP, A) 160067 (JP, A) JP-A-8-160066 (JP, A) JP-A 64-10664 (JP, U) JP-A 7-16165 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01P 15/12 H01L 29/84

Claims (6)

(57) [Claims] 1. A diffusion resistance for detecting stress is one plane.
A sensor element formed thereon and one end of the sensor element
A semiconductor acceleration sensor comprising:
Thus, one plane on which the diffusion resistance is formed is detected by the diffusion resistance.
Acceleration detection plane which is a plane orthogonal to the direction of the acceleration
And a side surface with respect to a surface facing the acceleration detection surface.
The pedestal is fixed to the sensor element at one end of the facing surface
The diffusion resistors are two P-type diffusion resistors and two N-type diffusion resistors.
A resistance, wherein the two P-type diffusion resistances correspond to the acceleration on the one plane.
The two N-type diffused resistors are provided in the vicinity of the degree detection surface, and the two N-type diffused resistors are
The N-type expansion
The distance between the diffusion resistance and the acceleration detection surface is the N-type diffusion resistance.
A semiconductor acceleration sensor that is shorter than a distance between the semiconductor acceleration sensor and the facing surface . 2. A base having an acceleration receiving surface, and a base provided on one side of the acceleration receiving surface.
And a sensing part for detecting a change in physical quantity , and one end of an opposing surface opposing the surface receiving the acceleration.
And a support fixed to the base.
In the semiconductor device, the strain sensing portion includes two P-type diffusion resistors and two N-type diffusion resistors.
A resistance, and the two P-type diffusion resistances determine the acceleration on the side surface.
The two N-type diffusion resistors are provided in the vicinity of the receiving surface, and the two N-type diffusion resistors are closer to the two P-type diffusion resistors.
The N-type diffusion
The distance between the resistance and the surface receiving the acceleration is the N-type diffusion resistance.
A semiconductor acceleration sensor having a distance shorter than a distance between the resistance and the opposing surface . 3. A short axis obtained by separating a semiconductor substrate,
The major axis is larger than the minor axis in the thickness direction of the semiconductor substrate.
A sensor element that is a solid formed by three sides of a certain height, and is disposed on one plane formed by the short axis and the long axis;
A diffusion resistance part for detecting stress, and a side surface of the one plane, which is formed by the major axis and the height;
Are the directions of acceleration detected by the diffusion resistance section.
And a support fixed to one of the two surfaces.
Semiconductor acceleration sensor, wherein the diffusion resistance section includes two P-type diffusion resistances and two N-type diffusion resistances.
And the two P-type diffused resistors are connected to the one plane on the one plane.
The two N-type diffusion resistors are provided in the vicinity of the other surface opposing the surface of the second P-type diffusion resistor.
The N-type expansion
The distance between the diffusion resistance and the other surface is equal to the N-type diffusion resistance.
A semiconductor acceleration sensor that is shorter than a distance between the first and second surfaces . 4. The P-type diffusion resistor and the N-type diffusion resistor
2. The method according to claim 1, wherein the first and second parts are arranged in parallel with each other.
The semiconductor acceleration sensor according to claim 3 . 5. The two P-type diffused resistors and two N-type diffused resistors.
Dispersion resistance is provided in parallel with the surface receiving the acceleration.
4. The method according to claim 1, wherein
2. The semiconductor acceleration sensor according to claim 1. 6. Two P-type diffusion resistors and two N-type diffusion resistors.
Sensor element with diffusion resistance part having resistance formed on one plane
And a pedestal for supporting one end of the sensor element.
A semiconductor acceleration sensor according to claim 1, wherein the diffusion resistance portion is formed on one surface of the diffusion resistance portion.
Is a plane perpendicular to the direction of acceleration detected by
Side surface with respect to the output surface and the opposing surface facing the acceleration detection surface
And the pedestal is fixed to the sensor element at one end of the facing surface.
And the two P-type diffused resistors are used to detect the acceleration on the one plane.
The two N-type diffused resistors provided on the output surface side,
It is located inside the one plane above the two P-type diffused resistors.
The diffusion resistance portion is located on the one plane.
In, this is formed to be unevenly distributed in the acceleration test exit surface side
And a semiconductor acceleration sensor characterized by the above-mentioned.