JPS61139719A - Semiconductive rotation sensor - Google Patents

Abstract

PURPOSE:To enhance sensitivity, by providing a slit to the central part of the beam in the vicinity of a cantilevered beam and forming piezoelectric resistor elements to both sides of the slit in parallel to the longitudinal direction of the cantilevered beam. CONSTITUTION:When the signal with resonant frequency of a cantilevered beam 1 is applied to a semiconductive rotation sensor from an oscillator 7 through an electrode 4, the free end 2 of the cantilevered beam 1 vibrates at the resonant frequency. When the cantilevered beam 1 is rotated around a rotary axis to the direction shown by the arrow in this state, Corioli's force shown by the arrow 10 is applied. This force is added to one side of a slit as compression stress and added to the other side thereof as tensile stress. Because the slit 6 is provided to the central part of the cantilevered beam 1 and a piezoelectric resistor element is formed in parallel to the longitudinal direction of the cantilevered beam 1, deformation stress can be concentrated to the piezoelectric resistor element and the stress of a largely deformable part can be detected and, therefore, sensitivity can be enhanced.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention vibrates a semiconductor single crystal cantilever at a predetermined frequency and detects the deformation that occurs in the cantilever depending on the rotation speed of one cantilever. This invention relates to a vibration-type semiconductor rotation sensor that detects rotational speed.

[Prior art]

As a semiconductor rotation sensor, there is one shown in FIG. 2, for example.

In Figure 2, (A) is a plan view, and (B) is A of (A).
-A' sectional view, (C) is an operation explanatory diagram.

In FIG. 2, a cantilever beam 2 of SL single crystal is mounted on a Si substrate 25.
0 is formed.

Then, when a signal having the resonance frequency of the cantilever beam 20 is applied from the oscillator 23 between the electrode 24 provided on the cantilever beam 20 and the Si substrate 25, the free end 24 of the cantilever beam 20
vibrates at a resonant frequency.

Then, when this semiconductor rotation sensor is rotated in the rotation direction shown by the arrow, a Coriolis force in the opposite direction to the rotation direction is applied to the cantilever beam 20 as shown by the arrow 26, and the cantilever beam 20
This causes kinked distortion.

By detecting this strain as a resistance change of the piezoresistive element 22 formed near the support portion of the cantilever beam 20, the rotation speed can be detected.

[Problem that the invention seeks to solve]

The conventional semiconductor rotation sensor as described above has a structure in which the detection is performed using a piezoresistive element formed perpendicular to the rotation axis on the cantilever beam after a force corresponding to the rotation speed (according to this structure, the cantilever beam (It is possible to detect only the deformation due to twisting of the cantilever beam without detecting deformation due to vibration.) Therefore, it was necessary to form the piezoresistive element across the center line (rotation axis) of the cantilever beam. However, the area around this center line is the area where the amount of deformation due to the force corresponding to rotation is minimal, and therefore there is a problem in that the sensitivity is low.

The present invention aims to solve the problems of the prior art as described above.

[Means to solve the problem]

In order to achieve the above object, in the present invention, a slit is provided in the center of the beam near the support part of the cantilever beam, and a piezoresistive element is formed on the side of the slit in parallel with the longitudinal direction of the cantilever beam. By doing this, the torsional deformation stress applied to the cantilever is concentrated on both sides of the slit, which is utilized to improve sensitivity.

[Embodiments of the invention]

FIG. 1 is a diagram showing an embodiment of the present invention, and (A) is a plan view;
(B) is a sectional view taken along the line AA' in (A), and (C) is an explanatory diagram of the operation.

In FIG. 1, a cantilever beam 1 made of Si single crystal is formed on a Si substrate 8. As shown in FIG.

Further, a slit 6 is provided in the central portion of the cantilever beam 1 near the support portion 3.

Two piezoresistive elements 5 are formed on both sides of the slit 6 in parallel to the longitudinal direction of the cantilever beam 1.

When a signal at the resonant frequency of the cantilever beam 1 is applied from the oscillator 7 to this semiconductor rotation sensor via the electrode 4, the free end 2 of the cantilever beam 1 vibrates at the resonant frequency.

When this semiconductor rotation sensor is rotated in the direction of the arrow around the rotating shaft 9 in this state, a Coriolis force as shown by the arrow 1o is applied.

This force is applied as a compressive stress on one side of the slit 6 and as a tensile stress on the other side, as shown by arrows 11 and 12.

By detecting this stress with the piezoresistive element 5,
Rotation speed can be detected.

In the above configuration, the slit 6 is provided in the center of the cantilever beam 1, and the piezoresistive element 5 is formed parallel to the longitudinal direction of the cantilever beam 1, so that the cantilever beam can rotate in response to rotation. The deformation stress generated in the beam can be concentrated on the piezoresistive element, and the tensile stress and compressive stress in areas where the deformation is large away from the center line where the cantilever beam does not deform can be detected. , sensitivity can be improved.

Note that in the above configuration, the piezoresistive element also detects stress due to vibration of the cantilever beam. However, while the same amount of stress is applied to the two piezoresistive elements, the stress due to rotation becomes tensile stress on one element and compressive stress on the other element, so the two piezoresistors If the devices are connected so as to detect the difference in the output of the elements, only the stress corresponding to rotation can be detected.

Furthermore, since the stress caused by vibration has a constant waveform corresponding to the applied voltage, the structure may be such that the value is subtracted from the output of the piezoresistive element.

Next, FIG. 3 is a manufacturing process diagram of the semiconductor rotation sensor of the present invention as described above.

In FIG. 3, first, in (A), an n-type epitaxial layer 31 corresponding to the thickness of a cantilever is grown on a p-type Si wafer 30 whose main surface is a <100> plane.

For example, when the cantilever beam is vibrated at a resonant frequency of about 300 Hz, the thickness of the n-type epitaxial layer 31 is about 30 mm when the length of the cantilever beam is about 500 mm.

Next, in (B), using the SiO□ film 32 formed on the n-type epitaxial layer 31 as a mask, a p-type impurity (for example, boron) is added to S in a pattern as shown in (B').
It diffuses into the n-type epitaxial layer 31 until it reaches the i-wafer 30.

Note that (B) shows the AA' cross section of (B').

Next, in (C), use the same method as above (C'
) A p-type piezoresistor 35 is diffused and formed in a pattern as shown in FIG.

Note that (C) shows a B-B' cross section of (C').

Next, in (D), a window is opened in the portion of the SiO□ film 32 that will become the electrode 4 by etching.

Next, in (E), a Cr-Au film 36, which will serve as a mask during electrolytic etching described later, is deposited by vapor deposition or sputtering, and then an Au layer 37 is deposited on top of the Cr-Au film 36, which is then etched leaving the necessary portions. Remove.

Next, in (F), the 513N4 film 38 is applied to the main surface on the opposite side.
is deposited by CVD or the like, and etched leaving only the necessary portions.

Next, ethylenediamine + pyrocatechol or KO
The Au layer 37 is immersed in an electrolytic etching solution such as H, and connected to a PT electrode immersed in the same etching solution so that the Au layer 37 has a positive potential, and a voltage is applied to perform electrolytic etching.

As a result, the p-type portion is etched, and a cantilever beam 39 is formed as shown in (G).

Note that during the above electrolytic etching, the above (B) and (B)
Since the part of the p+ layer 33 of (I) is also etched,
), slits 6 are also formed at the same time.

Next, in (H), using the Au layer 37 as a mask, Cr
- By etching the Au layer 36, a voltage vi4 is formed.

Through the above steps, a semiconductor rotation sensor as shown in FIG. 1 can be manufactured.

〔Effect of the invention〕

As explained above, in the present invention, a slit is provided in the center of the beam near the support part of the cantilever beam, and piezoresistive elements are formed on the sides of the slit in parallel to the longitudinal direction of the cantilever beam. The deformation stress generated in the cantilever beam in response to five rotations can be concentrated on the piezoresistive element, and both the compressive stress and tensile stress in the portion where the deformation is large away from the center line where the beam is not deformed can be concentrated. Since it is possible to detect
This has the effect of improving sensitivity.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram of an example of a conventional device, and FIG. 3 is a diagram of a manufacturing process of the present invention. Explanation of symbols

Claims (1)

[Claims] A semiconductor single crystal cantilever supported parallel to a rotation axis, means for vibrating the free end of the cantilever at a predetermined frequency, and means for detecting the amount of deformation occurring in the cantilever in response to rotation. In the vibrating semiconductor rotation sensor, a slit is provided in the center of the beam near the support part of the cantilever, and a slit is provided in the vicinity of the support part of the cantilever on the side of the slit parallel to the longitudinal direction of the cantilever. A semiconductor rotation sensor characterized in that a piezoresistive element is formed in the semiconductor rotation sensor.