JPH0820408B2 - Limiting current type oxygen sensor and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a limiting current type oxygen sensor and a method for producing the same, and more particularly to a thin film type limiting current type oxygen sensor in which an ion conductor film and electrodes are formed by a thin film technique and a method for producing the same.

[0002]

2. Description of the Related Art A ceramic oxygen sensor using yttrium (Y) -stabilized zirconium oxide (ZrO2 --Y2 O3) as an ion conductor (solid electrolyte) has been known. In the bulk type ceramic oxygen sensor, a ZrO2 --Y2 O3 ionic conductor bulk is obtained by press molding and firing, and a Pt electrode having a catalytic action is formed by printing and firing a Pt paste.

In contrast to such a bulk type ceramic oxygen sensor, recently, in order to miniaturize, miniaturize, and mass-produce elements, a thin film type limit for forming a ZrO2 --Y2 O3 ionic conductor and an electrode by a thin film technique is applied. Current oxygen sensors have been proposed. This type of thin film type ceramic oxygen sensor is obtained, for example, by sequentially stacking a cathode electrode, an oxide ion conductor film, and an anode electrode on a substrate. In order to obtain the limiting current characteristic with the substrate side as the oxygen gas supply side in this thin film type ceramic oxygen sensor, a gas permeable substrate having a diffusion rate control of oxygen molecules is required as the substrate. As such a gas permeable substrate, for example, ZrO2
There is BN.

[0004]

The gas permeable substrate as described above has a large pore size of about 0.1 to 0.2 μm, and a thin film having excellent uniformity should be formed on this substrate by a sputtering method or the like. Is difficult. Therefore, in order to form a thin film having excellent uniformity, it is desirable to use a dense substrate. However, when a thin film type limiting current type oxygen sensor is formed using a dense substrate, in order to obtain good limiting current characteristics, gas can be supplied to the interface between the cathode electrode and the ionic conductor with diffusion rate control. The problem is how to form the gas diffusion layer. The present invention has been made in view of such circumstances, and an object of the present invention is to provide a thin film type limiting current type oxygen sensor capable of obtaining excellent limiting current characteristics and a method for manufacturing the same.

[0005]

According to the present invention, a cathode electrode is formed on a dense substrate, an oxide ion conductor film is formed so as to cover the cathode electrode, and an anode electrode is formed on the ion conductor film. In the limiting current type oxygen sensor having the structure described above, the oxide ion conductor film is formed in a state in which voids serving as gas diffusion holes are provided along the side wall of the cathode electrode.

The present invention also manufactures a thin film type limiting current type oxygen sensor as described above, by forming an oxide ion conductor film by oblique sputtering or oblique deposition, and by gas diffusion along the side wall of the cathode electrode. It is characterized by forming voids that become holes.

[0007]

According to the present invention, in a structure in which a cathode electrode, an oxide ion conductor film and an anode electrode are laminated on a substrate, a dense substrate is used by forming micro gas diffusion holes along the cathode electrode. Therefore, excellent limiting current characteristics can be obtained without using a special gas diffusion layer. Further, according to the manufacturing method of the present invention, gas diffusion holes can be automatically obtained by utilizing oblique sputtering or oblique deposition in the step of forming the oxide ion conductor film. Mass productivity of the sensor is improved.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 (a) and 1 (b) are a plan view and a sectional view taken along the line AA 'of a thin film type limiting current type oxygen sensor according to an embodiment of the present invention. In this embodiment, a ceramic substrate 1 which can be cut is used as the dense substrate. The surface of the substrate 1 is mirror-finished. A comb-teeth-shaped Pt cathode electrode 2 is formed on this substrate 1, and an oxide ion conductor film of ZrO 2 -8 mol% Y 2 is formed so as to cover the cathode electrode 2.
An O3 film (hereinafter simply referred to as a ZrO2-Y2O3 film) 3 is formed, and a Pt anode electrode 4 having a comb-teeth shape is formed thereon so as to overlap the cathode electrode 2.

As shown in FIG. 1 (b), the ZrO2-Y2O3 film 3 is in close contact with the upper surface and the left side surface of the cathode electrode 2, but not in the right side surface. The void 5 formed along the right side surface of the cathode electrode 2 serves as a gas diffusion hole.

A manufacturing process for obtaining such a structure will be described below. First, the Pt cathode electrode 2 is formed on the substrate 1 by sputtering using a metal mask. Next, Zr
The ZrO2-Y2O3 film 3 is formed by the sputtering method using the O2-Y2O3 ceramic target. At this time, the sputtering is performed in a state where the substrate is tilted at 45 ° with respect to the particles knocked out from the target. As a result, one side of the cathode electrode 2 is shaded to form the void 5 as shown in FIG. 1 (b). After that, the Pt anode electrode 4 is formed by a normal sputtering process.

Pt cathode electrode 2 and Pt anode electrode 4
In this embodiment, the comb teeth are arranged so as to face each other with the ZrO2-Y2O3 film 3 interposed therebetween as shown in the drawing. However, it is not always necessary that the Pt cathode electrode 2 and the anode electrode 4 have such a pattern arrangement that they vertically overlap. For example, the pattern arrangement may be such that the comb teeth of the Pt anode electrode 4 are inserted between the comb teeth of the Pt cathode electrode 2.

Specific numerical examples will be given. The ceramic substrate 1 is 5 mm × 5 mm × 0.2 mm, and the Pt cathode electrode 2 and the Pt anode electrode 4 are 20 pairs of comb teeth patterns having a film thickness of 0.2 μm and a line width and a line interval of 75 μm. The ZrO2 --Y2 O3 film 3 has a thickness of 0.5 .mu.m.

According to this embodiment, since the surface of the substrate 1 is dense, the Pt cathode electrode 3 and the ZrO2-Y2O3 film 3 formed thereon have good uniformity. Further, the gap 5 formed along the side wall of the cathode electrode 2 by the oblique sputtering of the ZrO2 --Y2 O3 film 3
It becomes a gas diffusion hole having a diffusion rate controlling property. As a result of performing oxygen gas measurement in an atmosphere of 400 ° C. using the element actually obtained, a very clear limiting current characteristic was obtained.

The present invention is not limited to the above embodiment. For example, in the embodiment, Z is used as the oxide ion conductor.
Although rO2 --Y2 O3 is used, the present invention can be applied to a thin film type oxygen sensor using another oxide ion conductor. Further, as a method for forming the oxide ion conductor film, oblique vapor deposition such as electron beam vapor deposition can be used, and similarly, gas diffusion holes can be formed along the cathode electrode.

[0015]

As described above, according to the present invention, it is possible to form a fine gas diffusion hole along the interface between the cathode electrode and the oxide ion conductor film by using the dense substrate, which is excellent. It is possible to realize a thin film type oxygen sensor capable of obtaining the limiting current characteristic.

[Brief description of drawings]

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

[Explanation of symbols]

1 ... Ceramic substrate, 2 ... Pt cathode electrode, 3 ... Zr
O2-Y2O3 film, 5 ... Pt anode electrode, 5 ... Void (gas diffusion hole).

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Issei Ishibashi 1-5-1 Kiba, Koto-ku, Tokyo Fujikura Ltd. (72) Inventor Yoshinori Kato 1-1-5 Kiba, Koto-ku, Tokyo Shares Fujikura in the company (56) Reference JP-A-6-160341 (JP, A)

Claims (2)

[Claims] 1. A dense substrate, a cathode electrode partially formed on the substrate, and a void that covers the cathode electrode and serves as a gas diffusion hole along a side wall of the cathode electrode. Limiting-current-type oxygen sensor, comprising: the oxide ion conductor film formed as described above; and an anode electrode partially formed on the oxide ion conductor film. 2. A step of partially forming a cathode electrode on a dense substrate, and a gas diffusion hole is formed along the side wall of the cathode electrode by oblique sputtering or oblique deposition on the substrate on which the cathode electrode is formed. A limiting current formula characterized by comprising a step of forming an oxide ion conductor film in a state where a void is provided, and a step of partially forming an anode electrode on the oxide ion conductor film. Oxygen sensor manufacturing method.