JPH03158731A - Semiconductor capacity type pressure transducer - Google Patents

Abstract

PURPOSE:To improve the accuracy by etching a silicon substrate into a diaphragm shape, and providing a semiconductor substrate which is provided with an electrode for capacitance detection at its center part and a glass substrate for a pedestal on the reverse surface of the center silicon substrate. CONSTITUTION:At the center part of the semiconductor silicon substrate 4 made of silicon single crystal, the diaphragm part 6 is formed, and the top surface of the center part surrounded with the diaphragm part 6 are connected by an electric conductor to an external circuit where a movable electrode 2 is formed. Further, the substrate 4 and glass substrate 3 are welded together by anode joining and a fixed electrode 1 which is equal in area to the electrode 2 is formed on the surface facing the electrode 2. Further, the pedestal glass plate 5 where a pressure port 8 is formed is welded to the substrate 4 by anode joining together with the substrate 3 to apply pressure to the diaphragm part 6, and the electrode 2 moves vertically in parallel with the applied pressure. Further, when the groove width 18 of the diaphragm part 6 is narrowed down, the vertical variation quantity of the electrode 2 becomes smaller with the applied voltage, so the gap between the electrodes 1 and 2 is set to several mum and the sensitivity is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a capacitive pressure transducer, in particular a semiconductor substrate in which a concave diaphragm portion serving as a detection portion is formed, a semiconductor substrate having a movable electrode, and a movable electrode. The present invention relates to a structure of a substrate having fixed electrodes facing each other.

[Conventional technology]

The structure of the conventional capacitive pressure transducer is disclosed in Japanese Patent Application Laid-Open No. 62-598.
As described in No. 28, No. 5g-160832, an electrode was formed on the surface of a silicon single crystal diaphragm, and when two pressures were applied to the diaphragm part, the electrode deformed into an arc shape.

[Problems that the invention attempts to solve]

In the above conventional technology, the thickness of the diaphragm part formed on the semiconductor substrate and the thickness of the movable electrode part formed on the diaphragm part (thickness of the movable electrode part = thickness of the movable electrode + thickness of the diaphragm part) are almost the same. Therefore, when pressure is applied, the diaphragm part (movable electrode part) draws a shape like the arc of a fan, and the gap between the movable electrode part and the diaphragm part is uneven at each point of each electrode part. becomes. This non-uniformity becomes more pronounced as the applied pressure increases, resulting in deterioration of linearity and measurement accuracy.In addition, if the area of the image electrode is expanded to improve accuracy, the diaphragm As the arc shape becomes larger, a contradiction occurs that does not necessarily lead to improved accuracy.

Therefore, an object of the present invention is to improve linearity and accuracy by causing the diaphragm to be displaced or deformed not in an arc shape but in vertical parallel motion when pressure is applied.

[Means to solve the problem]

In order to achieve the above purpose, a semiconductor substrate, a movable electrode formed on the upper surface of the semiconductor substrate, a diaphragm part with a thickness of about 25 μm formed by micromachining around the movable electrode, and a movable part parallel to the semiconductor substrate are used. A glass substrate having a fixed electrode with a gap of several μm and the same area as the movable electrode is welded by anodic bonding to form the diaphragm part of the semiconductor substrate, and the movable electrode is vertically displaced in proportion to the pressure. It consists of movable electrodes.

[Effect]

The semiconductor capacitive pressure transducer constructed in this way is composed of a diaphragm section, which undergoes displacement in response to applied pressure, and the movable electrode section surrounded by the diaphragm section is perpendicular to the applied pressure. Move in parallel. Therefore, each point on the movable electrode surface always maintains a uniform gap with each point on the opposing fixed electrode surface, which is different from the conventional movable electrode surface which deforms into an arc shape in response to applied pressure. difference.

Since a capacitance change proportional to pressure can be obtained, a pressure transducer with high linearity and precision can be obtained.

Furthermore, since the movable electrode moves vertically in parallel, the gap between the movable electrode and the fixed electrode can be several μm. Therefore, there is an advantage that high output sensitivity can be achieved.

By narrowing the width of the diaphragm part, it is also possible to reduce the amount of displacement of the movable electrode due to pressure.

〔Example〕

The present invention will be explained below using examples.

FIG. 1(a) is a block diagram showing an embodiment of a semiconductor capacitive pressure transducer according to the present invention. FIG. 1(b) is a plan view, and FIG. 1(a) is a sectional view taken along the line XY in FIG. 1(b). FIG. 1(c) shows its operating form.

In FIG. 1(a), there is a semiconductor silicon substrate 4 made of silicon single crystal, a diaphragm portion 6 is formed in the center of the semiconductor silicon substrate 4, and an upper surface of the central portion surrounded by the diaphragm portion 6. is wired so that it can be connected to an external circuit on which the movable electrode 2 is formed. (
The thickness from the diaphragm part 6 to the bottom part 9 shown here is around 25 μm for 1 atmosphere, although it depends on the maximum pressure to be measured. ) Also, the convex portion on which the movable electrode 2 is formed and the diaphragm portion 6 are formed by micromachining,
The difference between the upper surface of the semiconductor silicon substrate 4 and the movable electrode 2 is controlled to be several μm.

The back surface of the semiconductor silicon substrate 4 is also etched by micromachining, and the remaining thickness of the diaphragm portion 6 etched from the top surface and the thin plate portion of the pressure reservoir portion 7 etched from the back surface is determined by the pressure P from the pressure port 8. It becomes a diaphragm that can change sensitively in the pressure direction, and has a thickness of about 25 μm as described above.

Next, the semiconductor silicon substrate 4 and the glass substrate 3 are welded together by anodic bonding, and a fixed electrode 1 having the same area as the movable electrode 2 is formed on the surface facing the movable electrode 2. Like the movable electrode 2, this fixed electrode 1 is wired so that it can be connected to an external circuit. A variable capacitance is formed.

Since the pressure reservoir 7 of the semiconductor silicon substrate 4 becomes a diaphragm 6 that changes depending on the pressure, an introduction pipe is required to introduce pressure into the pressure reservoir 7. This is done by welding the substrate 4 together with the glass substrate 3 using anodic bonding. It becomes possible to apply pressure to the diaphragm part.

The capacitance used here is A C=ε−...(1) (C: capacitance, A: electrode area, d: gap between electrodes, ε
: relative dielectric constant), and the smaller the gap between the electrodes, the better the sensitivity.

From the above, according to the present invention, the movable electrode 2 is vertically translated in parallel by the applied pressure as shown in FIG. 1(Q). Furthermore, if the groove width 18 of the diaphragm portion 6 (difference with the movable electrode 2) is narrowed, the amount of vertical change in the electrode relative to the applied pressure will be reduced, so the gap between the fixed electrode 1 and the movable electrode 2 should be set to several μm. As shown in equation (2) above,
It is possible to increase the sensitivity. The groove width 18 of the diaphragm 6 is formed in a vertical shape by low-temperature microwave plasma etching in the illustration, but as shown in FIG. 6, it is possible to form the groove width 18 by anisotropic etching. Needless to say, at this time, the groove width 18' of the diaphragm 6 may be adjusted. In the conventional semiconductor capacitive pressure transducer, as shown in FIG. 2, the diaphragm portion forming the movable electrode 2' becomes arc-shaped in response to the applied pressure. The gap between electrode 2' and fixed electrode 1' is not necessarily uniform at each point on the electrode surface, causing deterioration in output linearity and accuracy on the low voltage side. However, in the configuration of the present invention, since the displacement of the movable electrode 2 moves perpendicularly to the applied pressure, the gap 10 between the electrodes is always uniform over the entire electrode surface, resulting in good output linearity and accuracy.

Next, a modified example of FIG. 1 will be shown.

A conventional capacitive pressure transducer is shown in Figure 1.

There was only one capacitance detection section, but in order to further improve accuracy, four new diaphragms of the same thickness were formed, and the four capacitance sections were configured in a bridge configuration, as shown in Figure 3(b). By doing so, it is possible to respond to minute pressure changes and achieve high accuracy. (Fig. 3(d)) Similar to Fig. 1, minute movable 1
Capacitance is detected between the pole 11 and the minute fixed electrode, and at the same time pressure is applied to the actuator movable part 13 and the actuator boat 14, the actuator movable part 13 changes up and down to block the actuator boat 14. This allows it to be taken out as a pressure signal to the outside and used as another movable part. Further, as shown in FIG. 3(C), the actuator movable portion 13 may be shaped like a triangular pyramid like the tip 13', thereby allowing more accurate control.

In addition, as shown in FIG. 4, which is a modification of FIG. 3, an electrode configuration in which the diaphragm thickness is changed (that is, by changing the height or providing a movable electrode 15, it is possible to create an electrode configuration for each month) Needless to say.

FIG. 5 is also one of the embodiments of the present invention, in which one
On the chip (or two chips), the entire detection section 16 (
This is an example in which a circuit section is formed in which a capacitor section), a temperature compensation circuit 17, and a correction circuit such as an amplifier circuit 17' are mounted.

In FIGS. 1, 3, and 4, the shape of the movable electrode 2 on the diaphragm 6 is square.

It goes without saying that the shape may be polygonal or round, as long as it faces the fixed electrode 1 set above.

〔Effect of the invention〕

As can be seen from the above description, the present invention provides a capacitive pressure transducer that has excellent linearity with respect to applied pressure and is highly accurate.

[Brief explanation of the drawing]

FIG. 1(a) is a structural sectional view of a semiconductor capacitive pressure transducer of the present invention, and FIG. 1(b) is a plan view of the present invention. Fig. 1(c) is a deformation diagram of the electrode surface when pressure is applied in the present invention, Fig. 2 is a deformation diagram of the electrode surface when pressure is applied in a conventional capacitive pressure transducer, and Figs. 3 and 4 are diagrams of the present invention. FIG. 5 is a diagram showing an embodiment of the invention, FIG. 5 is a diagram showing an implementation example of the invention, and FIG. 6 is a diagram showing an embodiment of the etching shape of the invention. 1.1'... Fixed electrode, 2,2'... Movable electrode (on the diaphragm), 3... Glass substrate, 4... Semiconductor silicon substrate, 5... Pedestal glass plate, 6... ...Diaphragm part, 7...Pressure pool part, 8...Pressure port, 9...Bottom part, 10...Gap, 11...
Microscopic movable electrode. 12... Micro fixed electrode, 13.13'... Actuator movable part, 14... Actuator port,
15... Movable electrode section with different height, 16... Overall detection section, 17.17'... Temperature compensation and amplification circuit, 18
...Groove width, 19...Entire mounting part. Figure 3 (OL) <a-> Figure 3 f 4 Figure 5

Claims (1)

[Claims] 1. A silicon substrate is etched to form a diaphragm, and a semiconductor substrate is provided with an electrode for capacitance detection in the center thereof, and a glass plate is provided with an opposing electrode on the top surface of the semiconductor substrate to form a diaphragm. A semiconductor capacitive pressure transducer characterized in that a glass substrate constituting a detection gap and a glass substrate for a pedestal are welded to the lower surface of a central silicon substrate by anodic bonding, and output is detected in proportion to pressure. . 2. A semiconductor capacitive pressure transducer according to claim 1, characterized in that a plurality of capacitance detection sections are combined. 3. A semiconductor capacitive pressure transducer according to claim 2, characterized in that the electrode height is changed by the combination configuration of the capacitive detection section. 4. A semiconductor capacitive pressure transducer according to claim 1 or 2, characterized in that an actuator structure is provided in the center for pressure detection.