JPH0712658A - Combination sensor comprising silicon - Google Patents

Abstract

PURPOSE: To interrupt external influence to reduce distorsion and stress caused by heat and improve the accuracy by providing a resistive element formed by silicon variously doped in a deformed area under a conductive type layer. CONSTITUTION: A conductive path 9, a resistance element 3, a conductive type layer 8, an earthquake material 20, a frame 21 and the lower area of a deformed area are formed by silicon. Strong p-doping for forming the conductive path 9 is introduced into the surface of an n-doped silicon wafer, a p-doped silicon wafer or an n-doped silicon wafer, and further weak n-doping is introduced to form a resistive element 3. In this case, the layer 8 is disposed in such a manner as to have electric contact with n-material of the wafer. The deformed area 1 is not covered with a dielectric insulating layer 23. Accordingly, the bimetal effect produced by a difference in coefficient of thermal expansion between silicon oxide or silicon nitride for forming the insulating layer 23 and silicon can keep the deformed area from being deformed.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a combination sensor made of silicon with at least one deformation area (1, 2) and at least one resistance element (3-7) in the deformation area (1, 2). .

[0002]

2. Description of the Related Art Combination sensors made of silicon are already known (Wong et al., IEEE Digest of T.
technical Papers, Transduc
rs85, pp. 26-29), the combined sensor comprises a deformation region and n-doped Si in the deformation region.
It comprises a resistive element made of p-doped silicon as covered by a layer. However, the sensor
A protective layer of silicon oxide is additionally provided in the deformation region.

[0003]

The above-mentioned problems are imposed on the present invention.

[0004]

In contrast to the prior art, the sensor according to the invention as characterized in the independent claims is
The problem is solved by the advantage that the deformation region consists exclusively of variously doped silicon. Because,
Because the coefficients of thermal expansion of differently doped silicon differ only slightly, and also produce only minimal thermal strain and stress. Therefore, the accuracy of this type of sensor is essentially better than that of a sensor composed of different materials.

Advantageous other configurations and refinements of the sensor described in the independent claim are possible by the measures specified in the dependent claims. In order to shield the resistance element from external influences and to insulate it towards the surface, the resistance element underlies a layer of the second conductivity type. The resistive element can also be contacted by a conductive path consisting of heavily doped silicon or, as long as the resistive element extends over the deformation region, by a metallic conductive band. The sensitivity of the sensor is improved if the deformation area is configured as a bending tongue or a membrane. By using multiple resistance elements in the deformation region, the characteristic curve of the sensor can be improved, for example by using four resistance elements in a bridge circuit. In the production of this sensor, it is possible to start with p-conducting as well as n-conducting wafers.

Embodiments of the present invention will now be described and detailed with reference to the drawings.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a vertical sectional view through an acceleration sensor,
In this case, seismic mass
e) 20 is suspended from an opposed bearing 21 which is rigidly fixed by the deformation zone 1 which is described as a bending tongue. When the structure is accelerated, the seismic material tilts and the deformation zone 1 bends.

In the vicinity of the rigidly fixed counter bearing 21, a longitudinal resistance element 3 in the deformation zone 1 is present.
This resistive element 3 underlies the layer 8 and is contacted by two conductive paths 9. Furthermore, on the opposite bearing 21, there is a metal contact 22, which has a direct contact to the conductive path 9. Insulation layer 23 with structure
Electrical contact between the metal contacts 22 and the counter bearing 21 or the layer 8 is prevented by the use of.

FIG. 2 shows the acceleration sensor according to FIG. 1 in plan view. The longitudinal cross section through the structure described in FIG. 1 occurs along straight lines I-I. The resistance element 3 can be brought into contact with the conductive path 9 and a metal contact 22 arranged oppositely on the opposite bearing 21 so that the electrical resistance of the resistance element 3 can be measured. In this case, the metal contact 22 is used to connect an external connection line. Furthermore, the position of the layer 8 is entered in FIG.

The first modification of the resistance element changes the resistance of the resistance element 3 based on the piezo effect of single crystalline silicon. The deformation of the deformation region 1 based on the change of the resistance,
As a result, the accompanying acceleration can be estimated.

Conductive path 9, resistance element 3, layer 8, seismic material 2
0, the frame 21, and the lower region of the deformation region 1 are made of silicon. Now, in the case of the following description, it is assumed that the sensor described herein was manufactured by processing an n-doped silicon wafer. However, in the case of the stoichiometric method, it is also possible to manufacture from p-doped silicon wafers. Into the surface of the n-doped silicon wafer is introduced a strong p-doping which forms the conductive paths 9. Furthermore, a weak p-doping is introduced, which forms the resistance element 3. In this case, it is important that the layer 8 is arranged such that it has electrical contact with the n-material of the wafer. Patterning methods for the production of seismic material, deformation zone 1 and frame 21 are known to the person skilled in the art. In the case of the structure shown here, it is particularly important that the deformation region 1 is not covered by the dielectric insulating layer 23. This kind of dielectric insulating layer 23 is usually made of silicon oxide or silicon nitride. The two materials have coefficients of thermal expansion that differ by about the power of ten of the coefficient of thermal expansion of silicon. When the surface of the deformation region 1 is covered with this type of insulating layer, the deformation region is deformed due to a change in temperature based on the so-called bimetal effect. Since the coefficients of thermal expansion of various doped silicons differ only slightly, the thermally limited flow of the characteristic curve of the sensor in the case of the geometries presented here of the acceleration sensor is: Decrease. Insulation of the conductive path 9 and the resistance element 3 is achieved by the above-mentioned n-doped layer 8
And the pn junction created by this layer. Further insulation of the deformation area is unnecessary.

FIG. 3 shows a deformation region 2 formed as a film.
Another embodiment with is shown. This sensor can be used as an acceleration sensor as well as a pressure sensor. Frame 24, deformation area 2 and seismic material 20
Is made of single crystalline silicon. Furthermore, the resistance elements 4 to 7 and the conductive path 9 are also made of silicon. For the sake of simplicity, the n-layer 8 has not been filled in. In order to obtain the same thickness over the entire deformation area, said layers 8 are correspondingly arranged such that this layer covers the entire area of the membrane. The resistance element 7 is enlarged so as to further extend to the frame 24. In the above case, the resistance element 7 is made of the metal conductive band 10.
May be contacted by.

By using a plurality of resistive elements 4, 5, 6, 7 it is possible to improve the accuracy of the sensor and the output signal. This means that, for example, the four resistance elements 4 to 7 are
It can be achieved by constructing together in a bridge, so that the temperature dependence of the electrical resistance is compensated.

The change in resistance exhibits various signs in response to pressure or tensile stress, and can therefore be enclosed as a Wheatstone bridge to improve the output signal.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing the shape of a sensor including a bent tongue.

2 is a plan view showing the shape of the sensor according to FIG.

FIG. 3 is a plan view showing the shape of a sensor including a membrane.

[Explanation of symbols]

1, 2 deformation region, 3, 4, 5, 6, 7 resistance element,
8 Second-conductivity-type layer, 9 Conductive path, 10
Conductive band, 20 seismic material (seismische M)
assembly), 21 opposite bearings, 22 metal contacts,
23 insulating layer, 24 frame

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Claims (8)

[Claims] 1. A combination sensor made of silicon comprising at least one deformation region (1, 2) and at least one resistance element (3-7) in the deformation region (1, 2), the sensor comprising a deformation region. A combination sensor made of silicon, characterized in that it consists exclusively of variously doped silicon in (1, 2). 2. Sensor according to claim 1, wherein the resistive element (3-7) comprises a layer of the first conductivity type and underlies a layer (8) of the second conductivity type. 3. Conductive path (9) in which the resistive element (3 to 7) consists of heavily doped silicon of the first conductivity type.
The sensor according to claim 1 or 2, which is contacted by. 4. The resistance element (3 to 7) is a deformation area (1,
Sensor according to any one of claims 1 to 3, which extends over 2) and is contacted by at least one metallic conductive band (10). 5. The sensor according to claim 1, wherein the deformation region (1, 2) is formed as a bent tongue or a membrane. 6. Sensor according to claim 1, wherein a plurality of resistance elements (4-7), preferably (4), are used in the bridge circuit. 7. The first conductivity type is p-conductivity and the second conductivity type is n-conductivity.
The sensor according to any one of items 1 to 7. 8. The first conductivity type is n-conductivity and the second conductivity type is p-conductivity.
The sensor according to any one of items 1 to 7.