JPH04232454A - Oxygen sensor - Google Patents

Abstract

PURPOSE:To provide an oxygen sensor using a solid electrolyte which is compact and light-weight and operates at ordinary temperatures without requiring a reference gas source. CONSTITUTION:Two silicon wafers 1, 7 are bonded together. The silicon wafers 1, 7 have diaphragm parts 2, 8 with many minute holes 2a, 8a, respectively. Layers 3, 9 of a solid electrolyte and electrodes 4, 10 are formed on the corresponding diaphragm parts 2, 8. Moreover, electrodes 5, 11 are formed in a cell in the diaphragm parts. A hole 12 is formed in the silicon wafer 7 to penetrate into the cell.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen sensor using a solid electrolyte.

0002

2. Description of the Related Art Conventional oxygen sensor systems using solid electrolytes include an electromotive force type and a limiting current type. Moreover, there are two types of shapes: bulk type and thin film type.

0003

However, the limiting current type requires calibration, and the electromotive force type uses a reference gas, so there are problems in that a separate reference gas source is required.

Furthermore, since the solid electrolyte used in the bulk type is thick, its impedance is high at room temperature, and the operating temperature is
There is also the problem that measurements cannot be made unless the temperature is raised to about 00°C.

The present invention was made in view of the above problems, and its purpose is to provide an oxygen sensor that is small and lightweight, operates at room temperature, and does not require a separate reference gas source. There is a particular thing.

[0006]

[Means for Solving the Problems] The present invention to solve the above problems provides a first silicon wafer on which a first diaphragm portion in which a large number of fine holes are formed, and a first diaphragm portion formed with a plurality of fine holes. a first solid electrolyte layer formed on the outer surface of the first solid electrolyte layer, a mesh-shaped first electrode formed on the first solid electrolyte layer, and a mesh formed on the inner surface of the first diaphragm part. a second electrode bonded to the surface of the first silicon wafer opposite to the surface on which the first diaphragm portion is formed, and having a large number of fine holes drilled in the surface opposite to the bonding surface; a second silicon wafer on which a diaphragm portion is formed; a second solid electrolyte layer formed on the outer surface of the second diaphragm portion; and a mesh-like solid electrolyte layer formed on the second solid electrolyte layer. a third electrode, a mesh-shaped fourth electrode formed on the inner surface of the second diaphragm portion and connected to the second electrode, the second silicon wafer, and the second solid electrolyte. a hole penetrating the layer, the third electrode and the fourth electrode, a power source for applying voltage to the third and fourth electrodes, and a potential difference between the first electrode and the second electrode. It is equipped with a voltage measurement circuit that measures the voltage.

[0007]

[Function] In the oxygen sensor of the present invention, by applying a voltage to the third and fourth electrodes, the second solid electrolyte acts as an oxygen pump and is formed in the first and second diaphragm parts. Only oxygen in the gas to be measured is fed into the cell, and the oxygen concentration inside the cell is 100%. The first solid electrolyte is formed according to Nelson's equation,
Generates a voltage proportional to the logarithm of the ratio between the oxygen concentration in the cell (100%) and the oxygen concentration of the surrounding gas to be measured, and detects this voltage with a voltage measurement circuit to determine the oxygen concentration of the gas to be measured. .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to the drawings. Figure 1 is a cross-sectional configuration diagram of an embodiment of the present invention, and Figure 2 is Figure 1.
FIG. 3 is a diagram illustrating a main part of the manufacturing method of this embodiment, and FIG. 4 is a diagram illustrating a continuation of the manufacturing method shown in FIG. 3.

First, the configuration of the oxygen sensor of this embodiment will be explained using FIGS. 1 and 2. This embodiment has a configuration in which two processed silicon wafers are bonded.

First, one silicon wafer will be explained. In the figure, a first silicon wafer 1 has a first
A diaphragm portion 2 is formed, and the first diaphragm portion 2 is provided with a large number of fine holes 2a. A first solid electrolyte layer 3 is formed on the outer surface of the first diaphragm portion 2, and a mesh-shaped first electrode 4 is further formed on the first solid electrolyte layer 3.

Furthermore, a mesh-like second electrode 5 is formed on the inner surface of the first diaphragm portion 2. and,
An insulating film 6 is formed on the outer surface of the first silicon wafer 1 except for the solid electrolyte layer 3 .

On the other hand, the second silicon wafer 7 to be bonded to the surface opposite to the surface on which the first diaphragm portion 2 of the first silicon wafer 1 is formed has a surface opposite to the surface S to be bonded to the first silicon wafer 1. A second diaphragm portion 8 is formed in which a large number of fine holes 8a are bored on the surface side. A second solid electrolyte layer 9 is formed on the outer surface of this second diaphragm portion 8, and a mesh-shaped third electrode 10 is further formed on this second solid electrolyte layer 9. . Further, on the inner surface of the second diaphragm portion 8, a mesh-shaped fourth electrode 11 is formed to be connected to the second electrode 5. The second silicon wafer 7 includes a second silicon wafer 7, a second solid electrolyte layer 9, a third electrode 10, and a fourth electrode.
A hole 12 passing through the electrode 11 is formed.

[0013] Also, on the outer surface of the second silicon wafer 7, a second
An insulating film 13 is formed in a portion other than the solid electrolyte layer 9 .

Next, the electrical connections of the oxygen sensor of this embodiment will be explained. The third electrode 10 and the fourth electrode are connected to a negative electrode and a positive electrode of a power source 14, respectively, so that a constant voltage is applied thereto. On the other hand, the first electrode 4 and the second
The electrode 5 is connected to a differential amplifier 15 so that the voltage of the first electrode 4 can be measured.

Next, a method for manufacturing the oxygen sensor of this embodiment will be explained using FIGS. 3 and 4. In the figure, first,
By machining, etching, etc. on silicon wafers 1 and 7,
Diaphragm parts 2 and 8 having a diameter of about 5 to 10 mm and a thickness of about 100 to 50 μm are formed (steps 1 and 2).

Next, a stop layer 31 is formed on the inner surface of the diaphragm parts 2 and 8 (step 3).

A resist layer 32 is formed on the outer surface of the silicon wafers 1 and 7 (step 4). The resist layer 32 is patterned (step 5), and a large number of fine pyramidal holes 2a, 8a with opening diameters of 1 μm or less are formed by photolithography (step 6).

The resist layer 32 is removed and a new resist layer 33 is formed (step 7).

An insulating layer 34 is formed on this resist layer 33 by sputtering (step 8), and then the resist layer 33 is removed by a lift-off method to form insulating films 6 and 13 (step 9).

[0020] Remove the stop layer 31 (step 10)
, a mesh-like second electrode 5 and fourth electrode 11 are formed on the inner surfaces of the diaphragm parts 2 and 8 (step 11).

Solid electrolyte layers 3 and 9 such as zirconia (YSZ; yttria-stabilized zirconia in this example) are sputtered on the diaphragm parts 2 and 8 (step 1).
2). Mesh-shaped first and third electrodes 4 and 10 are formed on the solid electrolyte layers 3 and 9 (step 13).

Further, a hole 12 is provided in the second silicon wafer 7 to pass through the second silicon wafer 7, the second solid electrolyte layer 9, the third electrode 10, and the fourth electrode 11.

The first silicon wafer 1 and the second silicon wafer 7 manufactured in this way are bonded (step 14).
).

Next, the operation of the above configuration will be explained. By providing the oxygen sensor configured in this way in the gas to be measured and applying a voltage to the third electrode 10 and the fourth electrode 11 from the power source 14, the second solid electrolyte layer 9 acts as an oxygen pump. , only oxygen in the gas to be measured is fed into the cell C formed in the first and second diaphragm parts 2 and 8, and the oxygen concentration in the cell C becomes 100%. Furthermore, cell C
Excess oxygen inside is discharged to the outside through the hole 12.

The first solid electrolyte layer 3 generates a voltage E proportional to the logarithm of the ratio of the oxygen concentration (100%) in the cell to the oxygen concentration of the surrounding gas to be measured, according to Nelson's equation shown below. . E=(RT/4F)Ln(Px/P100) E: Electromotive force R: Gas constant F: Faraday constant Px: Oxygen partial pressure in the gas to be measured P100: Oxygen partial pressure in cell C (100%) T: Environmental temperature By detecting this voltage E with a differential amplifier, the oxygen concentration of the ratio measurement gas can be determined.

[0026] According to the above configuration, since the sensor itself generates the reference oxygen concentration, there is no need for a conventional reference gas source. Furthermore, since the solid electrolyte layers 3 and 9 are very thin, their impedance is sufficiently low even at room temperature, and the operating temperature can be kept at room temperature. Furthermore, since the oxygen sensor of this embodiment is manufactured using a thin film manufacturing method, it is small and lightweight.

It should be noted that the present invention is not limited to the above embodiments. For example, an amplifier and a power source may be formed on the same silicon wafer for further integration.

[0028]

As described above, according to the present invention, it is possible to realize an oxygen sensor that is small and lightweight, operates at room temperature, and does not require a separate reference gas source.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional configuration diagram of an embodiment of the present invention.

FIG. 2 is an enlarged view of part A in FIG. 1;

FIG. 3 is a diagram illustrating a main part of the manufacturing method of this example.

4 is a diagram illustrating a continuation of the manufacturing method shown in FIG. 3. FIG.

[Explanation of symbols]

1 First silicon wafer 2 First diaphragm 2a hole 3 First solid electrolyte layer 4 First electrode 5 Second electrode 7 Second silicon wafer 8 Second diaphragm 8a hole 9 Second solid electrolyte layer 10 Third electrode 11 Fourth electrode 12 Hole 14 Power supply 15 Differential amplifier (voltmeter)

Claims (1)

[Claims] 1. A first silicon wafer on which a first diaphragm portion having a large number of fine holes is formed, and a first solid electrolyte layer formed on the outer surface of the first diaphragm portion. a mesh-like first electrode formed on the first solid electrolyte layer; a mesh-like second electrode formed on the inner surface of the first diaphragm; and a mesh-like second electrode formed on the first solid electrolyte layer. A second diaphragm part is bonded to the surface of the wafer opposite to the surface on which the first diaphragm part is formed, and a second diaphragm part having a large number of fine holes bored therein is formed on the surface opposite to the bonding surface.
a silicon wafer, a second solid electrolyte layer formed on the outer surface of the second diaphragm part, a mesh-shaped third electrode formed on the second solid electrolyte layer, and the second solid electrolyte layer. a mesh-like fourth electrode formed on the inner surface of the diaphragm portion and connected to the second electrode;
silicon wafer, the second solid electrolyte layer, and the third solid electrolyte layer.
a hole penetrating the electrode and the fourth electrode, a power source for applying voltage to the third and fourth electrodes, and a voltage measurement for measuring the potential difference between the first electrode and the second electrode. An oxygen sensor comprising a circuit.