JPS58102567A - Semiconductor pressure transducer - Google Patents

Abstract

PURPOSE:To obtain a device resistant to noises, by forming a piezoresistive element on a substrate via an insulation layer, and surrounding the outer periphery thereof by a conductor layer. CONSTITUTION:A piezoresistor constituted of P type single crystal Si has good linearity of pressure-resistance and can take out the output in forward-reverse directions having good symmetry, in the plane (100) and the direction <110> wherein the piezoresistance coefficient becomes the maximum. Therefore, by constituting the substrate 1 and the conductor layer 5 of P type single crystal semiconductor the same as the piezoresistive element 3, a P-N junction is not formed, and accordingly electrically and mechanically good matching ca be obtained. By impressing a positive potential with the highest circuit voltage on the conductor layer 5 and the substrate 1 connected thereto, the piezoresistive element 3, in the periphery thereof, is surrounded by a shield plate having a higher potential, and negative ions contained in sealing solution are trapped to the conductor layer 5 or the substrate 1. Therefore, the output drift due to ion migration can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor pressure transducer using a piezoresistive element made of semiconducting crystal.

Conventionally, this type of semiconductor pressure transducer has a structure in which a piezoresistive region having a conductivity type different from that of the substrate is provided in a strain-generating portion that is provided approximately in the center of a semiconductor single crystal substrate and that generates strain in response to pressure. are doing.

Thus, in conventional semiconductor pressure and force transducers, the insulation between the piezoresistive regions is the same as the insulation between the piezoresistive regions and the substrate.
Since this is maintained by the N junction, there have been drawbacks such as a decrease in the S/N ratio due to leakage current between the PN junctions, especially at high temperatures.

In addition, especially when this pressure transducer is used in a sealed liquid such as silicone oil or fluorine oil as a pressure transmission medium, the output may take a long time due to the influence of the movement of ions contained in the filled liquid. The disadvantage of this method was that it allowed fluctuations (drift).

The present invention was made in view of the above-mentioned situation Kfs, and its purpose is to suppress output drift caused by leakage current and ion movement between piezoresistive regions,
The object of the present invention is to provide a semiconductor pressure transducer that is resistant to noise and capable of obtaining a stable output when energized.

In order to achieve such an object, the present invention provides a strain-generating portion provided approximately at the center of a semiconductor single crystal substrate.
An insulating layer made of a compound of It has layers.

In other words, by providing an insulating layer on a semiconductor single-crystal substrate and forming a piezo-resistive element made of a semiconductor single-crystal on top of the insulating layer, the piezo-resistive element can maintain its insulation as a completely insulated body. Therefore, it is possible to prevent leakage current as in the case of a conventional PN junction, and it is possible to use the device at a much higher temperature. In addition, conventionally, the depletion effect of the PN junction has caused a phenomenon in which the voltage and resistance are not proportional, but by interposing an insulating layer between the piezoresistive element and the substrate as described above, this This phenomenon can be effectively prevented.

In this case, since the insulating layer is formed from a semiconductor compound that constitutes the substrate and the piezoresistive element, the consistency at each interface is good, and it is possible to avoid distortion due to differences in thermal expansion coefficients, etc. can.

Furthermore, since the piezoresistive element is surrounded by a conductive layer through the insulating layer, this conductive layer functions as a Faraday shield, resulting in a structure that is resistant to noise. becomes. In particular, when a sealed liquid such as silicone oil or fluorine oil is used as a pressure transmission medium, the ions in the filled liquid are fixed to this conductive layer, so it is possible to suppress output drift due to the influence of ion movement. Can be done.

Examples will be described below.

FIG. 1 is a sectional view showing one embodiment of the present invention. In the figure, reference numeral 1 denotes a substrate made of P-type single crystal silicon. This substrate 1 is formed into a cup shape by removing a substantially central portion of the back surface of the substrate 1 by etching, and includes a diaphragm 1 in the center and a fixing portion 1 that supports the diaphragm 1 at its periphery.
It consists of b.

2 is an insulating layer made of silicon dioxide formed on the surface of the substrate 10; 3 is a piezoresistance element made of r-type single crystal silicon provided on the insulating layer 2 located above the diaphragm 1a; 4; 5 is a metallization batten serving as an electrode, and 5 is the insulating layer 2 on the piezoresistive element 3 except for the metallization batten 40.
This is a conductor layer made of T-type single crystal silicon formed so as to cover the conductor layer. This conductive layer 5 is connected to the substrate 1 through a through hole 6 provided in the insulating layer 2, and a bias voltage of the highest positive potential is applied to the conductive layer S and the substrate 1 by a power source 7. The voltage is applied via the metallization batten 8. Further, the piezoresistive cable 3 may be, for example, C
It can be formed by recrystallizing polysilicon deposited by the VD method by irradiating it with laser beams. In this case, the crystal axis direction of the recrystallized single crystal can be controlled by the scanning direction of the laser beam.

Generally, piezoresistors made of P-type single crystal silicon are N
It has better pressure-resistance adhesiveness compared to the shaped type,
(100) plane where the piezoresistance coefficient is maximum, <11.0
) output with good symmetry in both forward and reverse directions. In this case, in particular, as described above, the substrate, the plate 1, and the conductive layer 5t are also made of a P-type single crystal semiconductor similar to the piezoresistive element 3, so that a PN junction is not formed and electrical and mechanical provides the best consistency.

Furthermore, as described above, by applying the highest positive potential of the circuit voltage to the conductive layer 5 and the substrate 1 connected thereto, the piezoresistive element 3 is exposed to a shield plate having a higher potential than the surroundings. A shape surrounded by
Since the shadow ions contained in the filled liquid are trapped in the conductor layer 5 or the substrate 1, the output due to the movement of ions is
Drift can be avoided. .

FIG. 2 is a sectional view showing another embodiment of the present invention, and the same parts as in FIG. 1 are designated by the same symbols, and detailed explanation thereof will be omitted. That is, in the embodiment shown in FIG. 2, a conductive layer 11 made of metal is formed so as to surround the piezoresistive element 3 via an insulating layer 2, and a conductive layer 11 made of metal is formed at the contact portion with the substrate 1. An ohmic bias region 10 made of single crystal silicon is provided.

Such an ohmic contact region 10 is made of metal on a conductor, and when the impurity #1 degree of the substrate 1 is low,
This is necessary to obtain ohmic contact between the two.

In addition, in the above-mentioned embodiment, only the case where P-type silicon was used was explained, but when a piezoresistive element made of an N-type semiconductor is used, it is preferable that the conductor layer 4 is also made of an N-type semiconductor. , the conductor layer and the substrate are of course biased to the most negative potential.

Further, the conductor layer may be made of polysilicon.

As explained above, according to the present invention, a piezoresistive element tube is formed on a substrate via an insulating layer, and the outer periphery of this piezoresistive element is surrounded by a conductive layer. It has the excellent effect of making it possible to obtain a semiconductor pressure transducer that is strong against electricity and whose output stabilizes quickly in current-carrying class.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
FIG. 2 is a sectional view showing another embodiment of the present invention. 1... Board, 1h a fist/φ diaphragm, 1
b...Fixed part, 2...Insulating part, 3...0.
Piezoresistive element, 4@@@metallization" tongue 1
5, 9... Conductor layer. Patent applicant Yamatake Honeywell Co., Ltd.

Claims (1)

[Claims] A semiconductor single-crystal substrate exposed from a diaphragm-shaped strain-generating portion that strains in response to pressure and a fixed portion that supports the peripheral edge of the strain-generating portion, and a compound of the semiconductor formed on the strain-generating portion of this substrate. a piezoresistive element made of a semiconductor single crystal formed on the upper part of the insulating layer; a conductive layer covering at least the insulating layer on the piezoresistive element; and an electrode of the piezoresistive element. and a metallization pattern comprising a semiconductor pressure transducer.