JPH04258177A - Semiconductor strain detector - Google Patents

Abstract

PURPOSE:To reduce the entire size of a semiconductor strain detector by reducing the number of necessary gauge resistors from 16 to 4 pieces, and reducing errors caused by an irregularity in resistance values and resistance temperature coefficient of the resistors. CONSTITUTION:Four 4-terminal gauge resistors 2 are provided obliquely at 45 deg. from a crystal orientation direction <100> on a single crystalline silicon plate 1 in plane (100), and a shearing stress generated in a thin part is detected as a resistance value change according to a piezo resistance effect. Grooves 3 are formed in a lattice state in the <100> direction and the direction perpendicular to the <100> direction to pass directly under the resistors 2 so as to form a thin part. Leads 5 couple the terminals of the resistors 2 to a terminal connector 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor strain detector used for controlling the motion of industrial robots.

0002

[Prior Art] Conventionally, this type of semiconductor strain detector is shown in FIG.
It had the structures shown in (a) and (b). That is, on one surface of the (110) plane single crystal silicon plate 41, two to four gauge resistors 42 (Z1, Z2, Z3 and Z4) are arranged in the crystal orientation <110> direction,
Two to four gauge resistors 42 (Y1, Y2, Y3, and Y4) are arranged in the +45° direction from the crystal orientation <110> direction, and two to four gauge resistors 42 (Y1, Y2, Y3, and Y4) are arranged in the -45° direction from the crystal orientation <110> direction. Gauge resistance 42 (X1, X2, X3 and
4) were arranged, and gauge resistance groups in each direction (referred to as gauge resistance groups Z, Y, and X, respectively) were electrically connected to form a Wheatstone bridge. Further, a groove 43 is formed in a ring shape on the surface opposite to the surface on which the 6 to 12 gauge resistors 42 as described above are arranged, and the presence of this groove 43 forms a diaphragm portion 44. A gauge resistor 42 was placed at a fixed position on this diaphragm portion 44.

[0003] Note that the overline "￣" added to the Miller index representing a plane or crystal orientation within a crystal is herein indicated by an underline "_".

In this semiconductor strain detector, three gauge resistance groups X and Y each constitute a Wheatstone bridge.
and Z detect the vertical stress (compressive stress or tensile stress) generated in the diaphragm part 44 due to the force applied to the central part surrounded by the groove 43 as a change in resistance value due to the piezoresistance effect, and Each component in the X-axis, Y-axis, and Z-axis directions was detected.

Furthermore, in the manufacturing process of the conventional semiconductor strain detector, the groove 43 was formed by etching.

[0006]

[Problems to be Solved by the Invention] In the conventional semiconductor strain detector described above, in order to detect each component of the applied force in the X-axis, Y-axis, and Z-axis directions, three groups of two to four gauge resistors are used. Since they need to be arranged in the same direction, a total of 6 to 12 gauge resistors are required. Therefore, variations (irregular distribution) in the resistance value and resistance temperature coefficient between each gauge resistor are likely to occur, and errors due to these variations occur, and complex signal processing is required to correct the errors. There was a problem with that.

Furthermore, since the vertical stress generated in the diaphragm section is detected, it is necessary to arrange a pair of gauge resistors on the diaphragm section at a constant interval. Therefore, it is necessary to drill a relatively large groove, which poses a problem in that it becomes a constraint on reducing the size of the entire semiconductor strain detector.

Furthermore, since the grooves are formed by etching, there is a problem that the gauge resistor cannot be placed at a predetermined position on the diaphragm portion with good reproducibility due to variations in etching.

In view of the above points, an object of the present invention is to reduce the number of required gauge resistors from 16 to 4, thereby reducing errors caused by variations in resistance value and temperature coefficient of resistance between each gauge resistor. It is an object of the present invention to provide a semiconductor strain detector which can reduce the size of the entire semiconductor strain detector.

0010

[Means for Solving the Problems] The semiconductor strain detector of the present invention is arranged on a (100) plane single crystal silicon plate with crystal orientation <11.
Four 4-terminal gauge resistors provided at an angle of 45 degrees from the 0>direction;
The crystal orientation <11 passes directly under each of the terminal gauge resistors.
0> direction and in a direction perpendicular to the direction, a terminal connecting portion arranged on the outer periphery of the (100) plane single crystal silicon plate, each terminal of the four-terminal gauge resistor and the It has a lead part that connects to the terminal connection part.

[0011]

[Function] In the semiconductor strain detector of the present invention, the strain sensor is placed on a (100) plane single crystal silicon plate at an angle of 45° from the crystal orientation <110> direction.
The four 4-terminal gauge resistors installed at an angle detect the shear stress generated in the thin wall part as a resistance change due to the piezoresistance effect, and the groove passes directly under the 4-terminal gauge resistor to form the thin wall part. The lead portion connects each terminal of the four-terminal gauge resistor to the terminal connection portion.The lead portion connects each terminal of the four-terminal gauge resistor to the terminal connection portion.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained in detail with reference to the drawings.

FIGS. 1A and 1B are a plan view and a sectional view showing the structure of a semiconductor strain detector according to an embodiment of the present invention. The semiconductor strain detector of this example is (100)
It is formed on a plane single crystal silicon plate 1, and has four 4-terminal gauge resistors 2 (G1, G2, G3 and G4), four grooves 3 arranged in a lattice pattern, and each 4-terminal gauge resistor 2. It is configured to include 16 corresponding terminal connection parts 4, 4 of each, and 16 lead parts 5 that connect each terminal of the 4-terminal gauge resistor 2 and the terminal connection part 4.

The four-terminal gauge resistor 2 has a crystal orientation <11 on one plane on the (100) plane single crystal silicon plate 1.
It is installed at an angle of 45 degrees from the 0> direction. Regarding "4-terminal gauge resistance", please refer to "SIMULATION
OF MONOLITHICSILICON PR
ESSURE SENSOR CHIPS, You
ssof Fati and Hans R
Sensors Expo Pr
oceedings, Vol. 1, 1986” etc.

The groove 3 has two grooves in the crystal orientation <110> direction on the surface opposite to the surface on which the four-terminal gauge resistor 2 is provided.
One is provided, and two are provided in a direction perpendicular to that direction. Here, each groove 3 is provided to pass directly under each 4-terminal gauge resistor 2, and each 4-terminal gauge resistor 2 is located at a corresponding position on each side of the center of the rectangle formed by the four grooves 3. will be placed in

The four terminal connecting portions 4 correspond to one four-terminal gauge resistor 2, and are arranged on the outer periphery of the (100) plane single crystal silicon plate 1.

The lead portion 5 connects each terminal of the four-terminal gauge resistor 2 to the terminal connection portion 4.

FIGS. 2(a) and 2(b) are a plan view and a sectional view showing the structure of the four-terminal gauge resistor 2. FIG. The four-terminal gauge resistor 2 is formed of a thermal oxide film 7, an impurity diffusion layer 8, and a nitride film 9 on a (100) plane single crystal silicon plate 1. Note that the lead portion 5 connected to the four-terminal gauge resistor 2 is formed of an aluminum film 6.

FIGS. 3A to 3F are diagrams showing the manufacturing process of the semiconductor strain detector of this embodiment.

Next, the operation of the semiconductor strain detector of this embodiment constructed as described above will be explained.

The central part (groove 3) of the semiconductor strain detector of this embodiment
When a force is applied to the rectangular portion surrounded by the groove 3, a shearing stress is generated in the thin wall portion corresponding to the groove 3 (on which the four-terminal gauge resistor 2 is placed).

The generated shear stress is detected by each four-terminal gauge resistor 2 arranged in the thin wall portion corresponding to each groove 3 as the magnitude and polarity of a change in resistance value due to the piezoresistance effect. The detection result of the magnitude and polarity of this change in resistance value is based on the potential difference between two (output terminals) of the terminal connection parts 4 connected to each four-terminal gauge resistor 2 via the lead part 5. (The other two of the terminal connection parts 4 connected to each four-terminal gauge resistor 2 via the lead part 5 serve as input terminals to input a constant current to the four-terminal gauge resistor 2.) )
.

Based on the magnitude and polarity of the resistance change detected in this way, the X-axis of the force applied to the center,
The magnitude and direction of each component in the Y-axis and Z-axis directions can be detected. That is, the component in the X-axis direction is determined based on the two detection results of G1 and G2 of the four-terminal gauge resistance, the component in the Y-axis direction is determined based on the two detection results of G3 and G4, and G1 ,G2,G3
The component in the Z-axis direction is determined based on the four detection results of G4 and G4.

Next, the manufacturing process of the semiconductor strain detector of this embodiment will be explained with reference to FIGS. 3(a) to 3(f). The semiconductor strain detector explained in FIGS. 1 and 2 is formed by the following procedure.

■ The (100) plane single crystal silicon plate 1 is thermally oxidized to form a thermal oxide film 7 on the surface, and an impurity diffusion layer 8 is formed.
A window is opened to form a hole (see FIG. 3(a)). ■
An impurity diffusion layer 8 is formed by selectively thermally diffusing impurities such as boron in an oxidizing atmosphere (see FIG. 3(b)).
. ■ To protect the surface, low pressure CVD (Chemical
A nitride film 9 is formed by a vapor deposition method or the like (see FIG. 3(c)). (2) In order to establish an electrical connection with the impurity diffusion layer 8, the nitride film 9 and the oxide film 7 are etched to form a contact hole 10 (see FIG. 3(d)). (2) Terminal connection portions 4 and lead portions 5 are simultaneously formed using aluminum film 6 formed by vacuum evaporation or sputtering (see FIG. 3(e)). ■ Form the groove 3 using a mechanical processing method such as dicing (see Figure 3(f)).
. By forming such a lattice-like groove 3, only the central part of the rectangle surrounded by the groove 3 can move freely, the other parts are fixed, and the strain (force corresponding to the strain) that occurs in the central part becomes movable. ) can be detected.

Note that in the manufacturing steps shown in FIGS. 3(a) to 3(f), for the sake of simplicity, only one element of a semiconductor strain detector is formed. It is also possible to simultaneously manufacture a large number of semiconductor strain detectors by forming a plurality of elements and cutting and dividing them after formation.

[0027]

As described above in detail, according to the present invention, the number of gauge resistors required to detect forces having components in the X-axis, Y-axis, and Z-axis directions can be reduced from 16 to 4. Therefore, it is possible to reduce errors caused by variations in resistance value and temperature coefficient of resistance between each gauge resistance, and there is an effect that complicated signal processing for correcting such errors is not required.

Furthermore, since shear stress is detected as a change in resistance value using a four-terminal gauge resistor, it is sufficient to drill a relatively small groove, reducing the overall size of the semiconductor strain detector. This has the effect of making it possible.

[Brief explanation of the drawing]

FIG. 1(a) is a plan view showing a semiconductor strain detector according to an embodiment of the present invention, and FIG. 1(b) is a sectional view corresponding to the plan view shown in FIG. 1(a).

2(a) is an enlarged plan view showing the four-terminal gauge resistor in FIG. 1, and FIG. 2(b) is a sectional view corresponding to the plan view shown in FIG. 2(a).

3 is a diagram showing a manufacturing process of the semiconductor strain detector shown in FIG. 1. FIG.

4(a) is a plan view showing an example of a conventional semiconductor strain detector, and FIG. 4(b) is a sectional view corresponding to the plan view shown in FIG. 4(a).

[Explanation of symbols]

1 (100) plane single crystal silicon plate 2 4-terminal gauge resistance 3 groove 4 Terminal connection part 5 Lead part 6 Aluminum film 7 Thermal oxide film 8 Impurity diffusion layer 9 Nitride film 10 Contact hole

Claims (1)

[Claims] 1. Four 4-terminal gauge resistors provided on a (100)-plane single-crystal silicon plate at an angle of 45° from the <110> crystal orientation, and the 4-terminal gauge on the (100)-plane single-crystal silicon plate. on the surface opposite to the surface on which the resistor is provided, a groove passing directly under each of the four-terminal gauge resistors and provided in a lattice shape in the crystal orientation <110> direction and in a direction perpendicular to that direction; 1. A semiconductor strain detector comprising: a terminal connection portion disposed on the outer periphery of a planar single-crystal silicon plate; and a lead portion connecting each terminal of the four-terminal gauge resistor to the terminal connection portion.