JPH0795058B2 - Limiting current type oxygen sensor - Google Patents

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 an oxide ion conductor, and more particularly to a thin film type limiting current type oxygen sensor.

[0002]

2. Description of the Related Art Among oxygen sensors using an oxide ion conductor such as zirconia, a so-called limiting current type oxygen sensor utilizes a limiting current characteristic obtained by limiting the supply amount of oxygen gas to electrodes. is there. A conventionally known limiting current type oxygen sensor has a structure as shown in FIGS. 3 (a) to 3 (d). Of these, FIGS. 3 (a) to 3 (c) are called bulk type (thick film type). In FIG. 3A, the Pt cathode electrode 2 and the anode electrode 3 are formed on both surfaces of the ZrO ₂ —Y ₂ O ₃ sintered body substrate 1 having ionic conductivity by a printing method.
The element chip on which is formed is supported on the support base 4 by the glass material 5 with a predetermined space. Support base 4
A small gas diffusion hole 6 is formed in the
A heater 7 for activating the rO ₂ —Y ₂ O ₃ sintered body substrate 1 is provided. In FIG. 3B, contrary to FIG. 3A, the gas diffusion hole 6 is formed on the element chip side. Figure 3
FIG. 3C is an example in which the supporting gas 4 and the glass material 5 in FIG. 3B are integrally molded.

On the other hand, FIG. 3 (d) shows a so-called thin film type in which a cathode electrode 2 ', an oxide ion conductor film 1', and an anode are formed on a gas permeable substrate 8 by a thin film technique such as sputtering. The electrodes 3'are sequentially formed. In this structure, the gas permeable substrate 8 serves to limit the gas supply amount to the cathode electrode 2 '. The bulk type limiting current type oxygen sensor as shown in FIGS. 3 (a) to 3 (c) has a complicated processing process and is not suitable for mass production. Considering mass productivity, the thin film type as shown in Fig. 3 (d) is superior.

[0004]

However, the conventional thin film type limiting current type oxygen sensor has the following problems.
The cathode electrode and the anode electrode are, for example, Pt electrodes, which are formed by the sputtering method as described above.
When electrodes are formed on the entire surface of the chip as shown in (d), it is necessary to make them gas permeable, that is, to form a porous film. This is because the oxygen molecules supplied from the substrate 8 are ionized at the interface of the cathode electrode 2'with the ionic conductor 1 ', and as an ionic current, the ionic conductor film 1'.
This is because it is necessary to have a flow of flowing through the anode electrode 3 ', converted again into oxygen molecules at the anode electrode 3', and discharged. It is possible to form a porous Pt electrode by sputtering at a pressure near atmospheric pressure, but controlling the degree of porousness is not easy. Therefore, the reproducibility of element characteristics is low.
Further, the porous Pt electrode does not rely on sufficient sputtering and is only physically deposited on the surface of the Pt electrode, so that the bonding characteristics of the electrode are poor. That is, good voltage-current characteristics cannot be obtained, and peeling may occur, resulting in insufficient reliability. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thin film limiting current type oxygen sensor capable of improving the reproducibility of the electrode bonding characteristics and element characteristics.

[0005]

The present invention provides a limiting current type oxygen sensor comprising a cathode electrode, an oxide ion conductor film and an anode electrode laminated on a gas permeable substrate. Is a comb-shaped pattern, and these are formed in a state in which they are 180 ° out of phase with each other.

[0006]

According to the present invention, the cathode electrode and the anode electrode are arranged above and below the ion conductor film in a comb pattern and 180 ° phase-shifted, so that the cathode electrode, the anode electrode and the ion conductor film are formed. It is possible to secure a sufficiently large contact area. Moreover, since the electrodes have a comb-shaped pattern, oxygen can be supplied to the interface between the cathode electrode and the ion conductor film through the gap. Therefore, both the cathode and anode electrodes
Formed as a dense film under general sputtering conditions, while maintaining excellent electrical and mechanical electrode bonding characteristics,
It can perform the same electrode function as in the case of a porous electrode film. Further, a mechanically strong electrode joint can be obtained, so that the sensor has high reliability. For the same reason, the reproducibility of element characteristics is also excellent.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view and an AA ′ sectional view of a limiting current type oxygen sensor according to an embodiment of the present invention. In this example, as a gas permeable substrate, ZrO ₂ -BN (B
N10%) substrate 11 on which a Pt cathode electrode 12 and an oxide ion conductor film of ZrO ₂ -8 m are used.
The ol% Y ₂ O ₃ film 13 (hereinafter, simply referred to as ZrO ₂ —Y ₂ O ₃ film) and the Pt anode electrode 14 are sequentially stacked. As shown in FIG. 1 (a), the cathode electrode 1
2 and the anode electrode 14 have a comb-shaped pattern, and they are stacked 180 degrees out of phase with each other. The cathode electrode 12, the ZrO ₂ —Y ₂ O ₃ film 13 and the anode electrode 14 are all formed by sputtering under reduced pressure.

The ZrO ₂ --Y ₂ O ₃ film 13 is formed by, for example, a reactive sputtering method using a Zr-8 mol% Y alloy target and a mixed gas of argon and oxygen as a carrier gas. Since the sputtering rates of Zr and Y are almost the same, there is almost no change in composition between the target and the film formed by sputtering. In addition, ZrO ₂
-Y ₂ O ₃ in advance to create a ceramic target, a method of sputtering this is. Either method can be used.

Specific data will be described below. ZrO ₂
-BN substrate 11 has a thickness of 0.2 mm, and cathode electrode 12 and anode electrode 14 both have a thickness of 0.3 μm and Zr.
The thickness of the O ₂ —Y ₂ O ₃ film 13 was 0.6 μm. The size of the sensor chip is 5 mm × 5 mm, and the comb teeth of the cathode electrode 12 and the anode electrode 14 have a width of 7 mm.
There are 33 lines with a pitch of 5 μm and a pitch of 75 μm, that is, 33 pairs.
The limiting current characteristics of the device obtained under such conditions are shown in FIG. As shown in the figure, the rise of the voltage-current characteristic is steep, and the ZrO ₂ − of the cathode electrode 12 and the anode electrode 14 −
It is shown that the bonding characteristics with respect to the Y ₂ O ₃ film 13 are good. Also, clear limiting current characteristics are obtained.

An element was made with a reduced sensor size. That is, the size of the sensor chip is 2.5mm x 2.5mm
The cathode electrode and the anode electrode had a width of 50 .mu.m and a pitch of 50 .mu.m, and there were 22 pairs. In this case as well, excellent characteristics similar to those of the above-described examples were obtained.

In the examples, one of the stabilized zirconia ZrO ₂ --Y ₂ O ₃ was used as the oxide ion conductor.
Other metal oxide ceramics can be used. For example, the present invention is effective when a stabilized zirconia in which Yb ₂ O ₃ or the like is substituted and dissolved is used instead of Y ₂ O ₃ .

[0012]

As described above, according to the present invention, by arranging the cathode electrode and the anode electrode sandwiching the oxide ion conductor film in a comb shape of a predetermined pattern, a thin film type having excellent device characteristics can be obtained. A limiting current type oxygen sensor can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a limiting current type oxygen sensor according to an embodiment of the present invention.

FIG. 2 is a diagram showing a limiting current characteristic of the sensor of the example.

FIG. 3 is a diagram showing a configuration example of a conventional limiting current type oxygen sensor.

[Explanation of symbols]

11 ... ZrO ₂ -BN substrate, 12 ... Pt cathode electrode,
13 ... ZrO ₂ —Y ₂ O ₃ film, 14 ... Pt anode electrode.

Continued Front Page (72) Inventor Issei Ishibashi 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Line Co., Ltd. (72) Yoshinori Kato 1-1-5, Kiba, Koto-ku, Tokyo Fujikura Electric Line Incorporated (56) References JP-A-62-198748 (JP, A)

Claims (1)

[Claims] 1. A gas-permeable substrate, a comb-shaped cathode electrode formed on the substrate, an oxide ion conductor film formed on the substrate on which the cathode electrode is formed, and the oxide ion. A limiting current type oxygen sensor, comprising: an anode electrode formed on a conductor film and having a comb pattern that is 180 ° out of phase with the cathode electrode.