JPH01315173A - Manufacture of semiconductor acceleration sensor - Google Patents

Abstract

PURPOSE:To precisely control the thickness of a cantilever support part by forming an acceleration detecting circuit on a (110) oriented silicon substrate, integrally shaping a stopper, a pedestal and an oscillator on the face of the substrate and paralleling the movement direction of the oscillator to the substrate face. CONSTITUTION:An acceleration detecting circuit is formed by the use of a (110) oriented silicon substrate 13, anisotropyetching is performed along the fixed shape of the substrate 13 from the substrate surface and at the same time a lower stopper 17 and the like which combine a cantilever 14, a dead weight 15, an upper stopper 16 and a pedestal are formed. The oscillating direction of the dead weight for detecting acceleration is paralleled to the substrate surface. Thereby the thickness of the cantilever support part for determining the sensitivity of acceleration detection of anacceleration sensor can be controlled precisely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a semiconductor acceleration sensor.

[Prior Art] In recent years, semiconductor acceleration sensors that can be made smaller and lighter have been attracting attention, and as a method for manufacturing them, an anisotropic etching method using an electrochemical phenomenon is used inside the ship. FIG. 3 shows an example of a conventional manufacturing method in the order of steps.゛The method is to first form an N-type semiconductor layer 2 on one side of a P-type semiconductor substrate 1 by a diffusion method or an epitaxial growth method, and then add a piezoresistor 3, which is an element part forming a PN junction, and wiring. 4. A substrate having a structure consisting of an insulating film 5 and a pad hole 6 is prepared. Then,
A circuit that converts acceleration into an electrical signal and a semiconductor strain gauge are manufactured (FIG. 3(a)).

Next, as shown in FIG. 3(b), electrochemical etching is performed to obtain a semiconductor thin film from the back surface of the substrate 1.

The principle is that when an N-type semiconductor is placed in an etching solution,
A positive voltage is applied to the extent that a silicon oxide film is generated by the anodic oxidation reaction, and etching proceeds from the back side, resulting in P
When reaching the N-type semiconductor from the N-type semiconductor surface, an oxide film is formed near the interface where the PN junction existed, and etching is stopped at that interface, leaving the N-type semiconductor layer 2, and forming the P-type semiconductor layer 2.
This method consists of etching only the type semiconductor substrate 1.

After obtaining a semiconductor thin film through such a process, the structure shown in Fig. 3 (
As shown in C), a resist 7 is applied and patterned to cut out a desired cantilever shape from the upper part of the substrate surface.

Next, as shown in FIG. 3(d), using the resist 7 as a mask, a desired cantilever shape is formed from the upper part of the substrate surface by anisotropic etching, and an acceleration sensor is formed as shown in FIG. 3(e). 1 q.

Note that FIG. 4 is a plan view of the substrate obtained in FIG. 3(e), in which 10 is a support frame, 11 is a cantilever, and 12 is a cantilever support portion. Finally, as shown in FIG. 5, a weight 18 made of gold or the like is attached to the cantilever 11.
A stopper 8 and a pedestal 9 for preventing the cantilever from breaking are added to the support frame 10 to form an acceleration sensor.

[Problems to be Solved by the Invention] In the above process, electrochemical etching provides good results for forming a relatively thick semiconductor thin film on the order of several tens of willows, but it certainly does not have a precision on the order of several tens of willows. However, it is extremely difficult to form a flat semiconductor thin film required for fabricating the cantilever support portion. It is known that the sensitivity of an accelerometer is inversely proportional to the square of the thickness of the cantilever support part fabricated to detect acceleration, and in order to suppress the variation to about 10%, the fabrication accuracy of the cantilever support part must be A few rabbits are required.

Therefore, using electrochemical etching in an oil bath,
There was a drawback in that the sensitivity variations between chips formed within one wafer became extremely large.

In addition, the conventional method requires a costly and complex process of separately preparing the stopper, pedestal, etc. for the cantilever breakage prevention 1 and joining them during assembly.

The present invention has been made in order to solve the conventional problems as described above, and it is possible to reliably control the thickness of the cantilever supporting part with precision, and also prevent the weight of the camera element and the cantilever from breaking. It is an object of the present invention to provide a means for simultaneously forming a stopper and a pedestal for prevention.

[Means for Solving the Problems] The present invention provides a method for manufacturing a semiconductor acceleration sensor having a structure in which a semiconductor substrate on which a vibrator including a cantilever and a weight and an acceleration detection circuit are formed is held between a stopper and a pedestal. (110) A step of forming an acceleration detection circuit on an oriented silicon substrate, and a step of etching the substrate surface into a predetermined shape to integrally form a stopper, a pedestal, and a vibrator from the silicon substrate. , a method of manufacturing a semiconductor acceleration sensor, characterized in that a movable direction of the vibrator is parallel to the substrate surface.

[Function] Since the semiconductor acceleration sensor of the present invention is configured such that the vibration direction of the weight for detecting acceleration is parallel to the substrate surface, the cantilever support portion is formed parallel to the substrate surface. It is not necessary to form a semiconductor (A thin film) for the purpose. Also, to miniaturize the acceleration sensor + J, it is necessary to shorten the length of the cantilever, but this will reduce the sensitivity. Since , is inversely proportional to the square of the thickness of the acceleration detection part, it is possible to make that part thin and accurate, making it possible to miniaturize the acceleration sensor. In order to increase the weight of the weight, other metals, such as gold, were added using the plating method, but since these weights allow the sensor to be formed perpendicular to the substrate surface, It can be formed directly from a semiconductor substrate.Also, stoppers are usually provided at the top and bottom of the cantilever to prevent damage to the sensor due to excessive acceleration loads.
This can also be produced from the substrate at the same time as the cantilever is formed. These things greatly simplify the assembly process.

[Example] Next, an example of the present invention will be described in detail with reference to the drawings.

A (110) oriented silicon substrate 13 as shown in FIG. 1 is used as the substrate to form an acceleration detection circuit.

FIG. 1(a) is a plan view of a substrate on which an acceleration detection circuit is formed, and FIG. 1(b) is a longitudinal sectional view taken along line AA' in FIG. 1(a). In the figure, since the structure of the acceleration detection circuit is the same as that of the conventional example, the same reference numerals are given to the same structural parts as in FIG. 3, and the explanation thereof will be omitted.

Next, this substrate 13 is anisotropically etched from the substrate surface into a predetermined shape as shown in FIG.
4. The weight 15, the upper stopper 16, the lower stopper 17 which also serves as a pedestal, etc. are formed at the same time.

Through the above steps, the acceleration sensor is assembled.

Normally, this semiconductor acceleration sensor has a package with
Since it is used while standing vertically and fixed, there is no need to take the trouble to raise the vibrator part, which consists of the cantilever and the weight, above the substrate surface. However, if it is desired to be fixed parallel to the package and used for measuring acceleration in the lateral direction, anisotropic etching is performed from the back surface of the substrate to an appropriate thickness.

This etching provides a pedestal on which the vibrator can vibrate freely. Next, the substrate may be anisotropically etched into a predetermined shape in the same manner as described above.

[Effects of the Invention] As described above, according to the present invention, it is possible to precisely control the thickness of the cantilever support portion that determines the acceleration detection sensitivity of the 7JO speed sensor υ. Also,
It is possible to form not only a cantilever for detecting acceleration from a semiconductor substrate, but also a weight for a vibrator, a stopper for preventing the cantilever from breaking, and a pedestal at the same time. From this, the production efficiency of the /J[l speed sensor is significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a plan view and a longitudinal sectional view of a substrate for explaining the present invention in detail, FIG. 2 is a plan view of an example of a semiconductor acceleration sensor obtained by the method of the present invention, and FIG. 3 is a conventional example. FIG. 4 is a plan view of the substrate obtained in the above steps, and FIG. 5 is a longitudinal cross-sectional view of an example of a conventional semiconductor acceleration sensor. . 1... P-type semiconductor substrate 2... N-type semiconductor layer 3
...Piezoresistor 4...Wiring 5...Insulating film 6...Pad hole 7...Resist
8... Stopper 9... Pedestal
10... Support frames 11, 14... Cantilever 12... Cantilever support part

Claims (1)

[Claims] (1) In a method for manufacturing a semiconductor acceleration sensor having a structure in which a semiconductor substrate on which a vibrator consisting of a cantilever and a weight and an acceleration detection circuit are formed is held between a stopper and a pedestal, an acceleration sensor is placed on a (110) oriented silicon substrate. The method includes a step of forming a detection circuit, and a step of etching the surface of the substrate into a predetermined shape to integrally form a stopper, a pedestal, and a vibrator from the silicon substrate, and the movable direction of the vibrator is aligned with the substrate. A method for manufacturing a semiconductor acceleration sensor, characterized in that the acceleration sensor is parallel to a plane.