JPH01236659A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To make possible a high-precision measurement and control by using a sensor by a method wherein groove parts are formed in a semiconductor substrate between a diaphragm and an electrode to inhibit a surface tension, which is generated at the time of probing, from propagating to the diaphragm. CONSTITUTION:Groove parts 8 are formed in a semiconductor substrate 1 between an electrode 4 and a diaphragm 2 by anisotropic etching, reactive ion etching or the like. Accordingly, a surface tension, which is generated at a time when a probing is executed using a probing terminal 11 for conducting a measurement of electric characteristics and an output control due to the trimming of a resistor for control by a sensor, is absorbed and interrupted in the groove parts 8 to prevent the stress from being applied to the diaphragm 2 and semiconductor distortion gauges 3. Thereby, a high precision measurement and a control become possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor pressure sensor having a semiconductor strain gauge as a pressure-electrical conversion element.

[Conventional technology]

As this type of semiconductor pressure sensor, conventional
As shown in the schematic plan view of the figure, a thin diaphragm 2 is formed in the center of a semiconductor substrate 1.
A semiconductor strain gauge 3 is disposed at a predetermined position, and an electrode 4 is formed around the semiconductor substrate 1 to be electrically connected to the semiconductor strain gauge 3. It guides electrical signals according to the information to external equipment. Furthermore, in recent years, a structure in which amplification, temperature compensation, and adjustment circuits are integrated on the surface of the semiconductor substrate 1 has also been developed.

By the way, such semiconductor pressure sensors are subjected to blowing to measure the electrical characteristics of the sensor and adjust the output at the end of the manufacturing process, and at that time, probe terminals made of tungsten etc. However, in order to keep the contact resistance low, a stylus pressure of about 3 to 5 gf is usually applied.

[Problem to be Solved by the Invention] As mentioned above, the inventors of the present invention have considered the fact that the probe terminal applies stylus pressure to the semiconductor substrate l during blowing, and as a result, it has been found that the stylus pressure caused by this stylus pressure is It has been found that the stress propagates and generates surface stress on the diaphragm 2, and that when this stress is applied to the semiconductor strain gauge 3, it acts as a change in resistance value, which is a hindrance to high-precision measurement and adjustment of the sensor.

Figure 3 shows the FEM analysis results showing the relationship between the distance χ from the electrode 4 as a load point to which stylus pressure is applied and the surface stress σ due to the stylus pressure at that position. These are the characteristics of this conventional semiconductor pressure sensor.

Note that the stylus pressure was set at 3 to 5 gf. As can be seen from the figure, in the conventional configuration, surface stress σ is generated even at a position 0.5 mm or more away from the electrode 4, causing a change in gauge resistance that poses a problem in terms of accuracy. Also, FIG. 5 shows the stylus force and sensor fluctuation output Δ■ in this conventional configuration.

This is a characteristic diagram showing the relationship between the sensor output and the sensor output.

The present invention has been made in view of the above-mentioned problems, and provides a semiconductor pressure sensor having a structure that suppresses surface stress caused by blobbing from propagating to the diaphragm and enables high-precision measurement and adjustment of the sensor. The challenge is to do so.

[Means to solve the problem]

In order to achieve the above object, the semiconductor pressure sensor of the present invention includes: a semiconductor substrate having a thin diaphragm; a semiconductor strain gauge formed on the main surface of the semiconductor substrate; and a semiconductor strain gauge formed on the main surface of the semiconductor substrate. , an electrode electrically connected to the semiconductor strain gauge, and a groove formed in the semiconductor substrate between the diaphragm and the electrode.

[Effect]

Therefore, according to the above configuration, the surface stress generated during blowing is blocked by the groove portion formed in the semiconductor substrate, and the stress no longer acts on the diaphragm and, by extension, the semiconductor strain gauge.

〔Example〕

Hereinafter, the present invention will be explained using embodiments shown in the drawings.

FIG. 1 shows a semiconductor pressure sensor according to an embodiment of the present invention, and FIG.
A line cross-sectional view is shown. In the figure, 1 indicates a chip size of 3 to
It is a semiconductor substrate made of a single crystal silicon substrate or the like with a 4M opening and a thickness of 150 to 400 μm, and a thermal oxide film 9 produced by thermally oxidizing silicon is formed on its main surface. Then, by ion-implanting P-type impurities such as boron (B) into four predetermined regions on the diaphragm 2, which will be described later, within the semiconductor substrate l,
A semiconductor strain gauge 3 of type conductivity type is formed. Also, in the same manner (implanting impurities such as boron at a high concentration into a predetermined region in the semiconductor substrate 1, electrically connecting the semiconductor strain gauges 3 to each other,
Diffusion wiring 5 having a low specific resistance for forming a bridge circuit is formed.

Then, electrodes 4 made of aluminum are formed in each region around the semiconductor substrate l by vacuum evaporation or the like, and at the same time electrodes 4 made of aluminum, diffusion wiring 5, and adjustment (trimming) made of thin films such as 5i-Cr are formed. A conductor wiring 6 is formed to electrically connect the resistors 10 to each other. Furthermore, a surface protection film 7 made of a silicon oxide film or the like is formed by CVD or the like, and the surface protection film 7 on the electrode 4 is partially removed.

Then, a trench 8 having a width of 100 to 300 .mu.m is formed by anisotropic etching, reactive ion etching, etc., in the semiconductor substrate Fi, 1 between the electrode 4 and the diaphragm 2, which will be described later. In the case of the present embodiment, the electrode 4 has a rectangular shape, and grooves 8 having a U-shaped plane are formed corresponding to three sides closer to the diaphragm 2 among the four sides of the electrode 4. Therefore, the conductor wiring 6 is led out from the remaining side of the electrode 4. still,
In FIG. 1(a), the groove portion 8 is distinguished by hatching.゛After that, etching is performed from the other main surface side of the semiconductor substrate 1 using an alkaline solution such as KOH, for example, 1.5 to 2 μm.
A thin film diaphragm 2 having a rectangular or circular shape and a thickness of 30 to 70 μm is formed to constitute the semiconductor pressure sensor of this embodiment.

In the semiconductor pressure sensor configured as described above, for example, when a detected pressure P acts on the diaphragm 2 from the other main surface side of the semiconductor substrate 1, the semiconductor strain gauge 3 is deformed along with the displacement of the diaphragm 2, and the piezoresistive effect is applied. The change in resistance value is output as an electrical signal from the electrode 4 to an external device.

According to this embodiment, in order to measure the electrical characteristics of the sensor and adjust the output by trimming the adjustment resistor at the final stage of the manufacturing process, the probe terminal 11 is used to blow the air as shown in FIG. Although the surface stress generated at that time is absorbed and cut off by the groove 8, the stress is applied to the diaphragm 2 and, by extension, the semiconductor strain gauge 3 in a state where no stress is applied. Therefore, even after the probe terminal 11 is separated from the electrode 4, its characteristics do not change.
A semiconductor pressure sensor that is measured and adjusted with high precision can be provided.

The electrode 4 when the groove 8 is formed with a width of 150 μm and a depth of 100 μm, and is provided at a position 100 μm apart from the electrode 4.
The relationship between the distance χ from the stylus pressure and the surface stress σ caused by the stylus pressure is shown in FIG. 3. According to FIG. It can be seen that almost no stress is generated at these positions.

Although the present invention has been described above using the example shown in FIG. 1, the present invention is not limited to this, and can be modified in various ways without departing from the spirit thereof. Bipolar IC, MOS in the thick part of
A signal amplification circuit or the like consisting of an IC or the like may be formed, or
The shape of the electrode 4 or the groove 8 may be other shapes such as a circle.

〔Effect of the invention〕

As described above, according to the present invention, since there is a structure in which a groove is formed in the semiconductor substrate between the diaphragm and the electrode,
This has the effect of suppressing the propagation of surface stress generated during blowing to the diaphragm, and enabling highly accurate measurement and adjustment of the sensor.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are diagrams representing an embodiment of the present invention,
Fig. 2 is a partial sectional view of Fig. 1(b) during blobbing, Fig. 3 is a relationship diagram between distance χ and surface stress σ, and Fig. 4 is a diagram showing the relationship between distance χ and surface stress σ.
This figure is a plan view of a conventional semiconductor pressure sensor, and FIG. 5 is a diagram showing the relationship between stylus pressure and fluctuating output of the conventional semiconductor pressure sensor. 1... Semiconductor substrate, 2... Diaphragm, 3...
Semiconductor strain gauge, 4... Electrode, 5... Diffusion wiring, 6
...Conductor wiring, 8...Groove portion, 10...Adjustment resistor. Representative Patent Attorney Takashi Okabe Figure 2 Snow shoveling distance #L (χ) Figure 3

Claims (1)

[Scope of Claims] A semiconductor substrate having a thin diaphragm, a semiconductor strain gauge formed in contact with the diaphragm, and an electrode formed on the main surface of the semiconductor substrate and electrically connected to the semiconductor strain gauge. and a groove formed in the semiconductor substrate between the diaphragm and the electrode.