JPH0587763A - Production of gas sensor - Google Patents

Abstract

PURPOSE:To obtain a gas sensor reduced in power consumption by printing gas-sensitive paste to patterns formed by developing a resist to wrap the same and removing the paste other than the patterns to uniformize the thickness of the patterns and baking the patterns to finely divide a gas detection film. CONSTITUTION:An SiO2 film 4 is formed to an Si substrate 2 and electrode patterns 8 composed of Rt and heater patterns 6 are formed to be coated with a photoresist 10. The photoresist 10 is prebaked and subsequently exposed and developed to form a gas-sensitive pattern 9. Further, stannic oxide paste 12 being gas-sensitive paste is printed on the pattern 9. The stannic oxide paste 12 is wrapped and the part built up from the photoresist 10 is removed. Thereafter, the whole is baked to remove the photoresist 10 and the paste 12 is sintered to obtain a gas-sensitive thick film. The gas-sensitive pattern 9 determined by the accuracy of the photoresist 10 can be obtained and this pattern 9 is finely divided to reduce the power consumption of the gas sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a gas sensor, and more particularly to a method for manufacturing a fine gas sensitive pattern.

[0002]

2. Description of the Related Art A gas sensor using a thin or thick film gas sensitive portion is well known. When such a pattern of the gas sensitive portion is called a gas sensitive pattern, it is indispensable to make the gas sensitive pattern fine in order to miniaturize the gas sensor. A commonly used technique for pattern miniaturization is etching. However, it is difficult to etch stannic oxide, indium oxide, etc., which are mainly used for gas sensors. In simple printing without etching, the shape of the gas sensitive pattern is limited to about 200 μm × 200 μm.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a gas sensor which enables a fine gas sensitive pattern. Moreover, a secondary problem in claim 1 is to make the thickness of the gas-sensitive thick film uniform.

[0004]

According to the present invention, a step of coating and developing a photoresist on a substrate to form a gas-sensitive pattern, a step of coating a paste of a gas-sensitive material on the gas-sensitive pattern and filling the pattern, and a filling step. The gas-sensitive paste is lapped to remove the gas-sensitive paste in the portion other than the pattern, and the step of aligning the thickness of the gas-sensitive paste in the pattern portion with the thickness of the photoresist as a reference, and baking the gas-sensitive paste. A method of manufacturing a gas sensor, which comprises a step of forming a gas sensitive film and removing a photoresist.

Further, according to the present invention, a step of coating and developing a photoresist on a substrate to form a gas-sensitive pattern, a step of forming a thin film of a gas-sensitive material on the gas-sensitive pattern, and removing the photoresist, And a step of removing a thin film of the gas-sensitive material in a portion other than the gas-sensitive pattern, the method for manufacturing a gas sensor.

[0006]

The pattern of the photoresist is filled with the paste of the gas sensitive material and then the pattern is lapped. Then, the paste of the gas-sensitive material on the portion other than the pattern is removed, and at the same time, the thickness of the paste is determined by the thickness of the photoresist. The photoresist pattern can be made extremely fine, for example, 10 μm × 10 μ
A pattern of about m can be obtained. Variations in paste thickness result in variations in gas sensor characteristics. However, since the paste thickness can be controlled by the photoresist thickness, the characteristics of the gas sensor can be made uniform. When the ratio of the thickness of the gas sensitive pattern to the width and length is called the aspect ratio,
The aspect ratio is determined by the gas sensitive pattern of the photoresist. This aspect ratio can be set to about 3, for example, and an appropriate aspect ratio can be obtained.

In the case of a thin film gas sensor (the film thickness of the gas sensing portion is 10 μm or less, more specifically 5 μm or less, more specifically 1 μm or less), a gas sensing portion having a predetermined pattern can be obtained by lift-off. it can. First, a thin film of a gas sensitive material is formed on a gas sensitive pattern of a photoresist by sputtering, vacuum deposition or the like. Next, the photoresist is removed with a solvent and ultrasonic vibration. Then, if the thickness of the photoresist is sufficiently larger than the thickness of the thin film of the gas-sensitive material, the thin film of the gas-sensitive material of the gas-sensitive pattern and the thin film in other parts are separated in the process of removing the photoresist, A thin film remains only in the pattern. When the thin film of the gas-sensitive material is thin and the thickness of the photoresist is large, even if the photoresist is removed by baking, the thin film of the gas-sensitive material on the resist and the thin film of the gas-sensitive material in the pattern are separated. The thin film of the gas sensitive material can be left only in the pattern.

[0008]

EXAMPLES Example 1 FIG. 1 shows a manufacturing process of an example. First, S is applied to the Si substrate by thermal oxidation of the substrate such as Si or sputtering of the silica film.
An iO2 film is formed. Then, an electrode pattern of Pt or the like and a heater pattern are formed by electroless plating or dry etching after overall surface sputtering. After this, a photoresist is applied. This state is shown in FIG. In the figure, 2
Is a Si substrate, 4 is a SiO2 film, 6 is a Pt heater pattern, 8 is a Pt electrode pattern, and 10 is a photoresist. The photoresist 10 is pre-baked, then exposed and developed to form the gas-sensitive pattern 9. This state is shown in FIG. After development, post-baking is performed to increase the strength of the photoresist, and stannic oxide paste, which is a gas-sensitive paste, is printed. The type of paste is not limited to stannic oxide, but indium oxide, tungsten oxide, Pt catalyst-added alumina used for catalytic combustion gas sensors, antimonic acid used for proton conductor gas sensors, β-alumina for solid electrolyte materials, etc. Is optional. This state is shown in FIG. Reference numeral 12 is a gas sensitive paste of stannic oxide, which is thicker than the photoresist 10. The printing accuracy is lower than the photoresist pattern accuracy, and the stannic oxide paste is wider than the gas sensitive pattern 9. Then, the stannic oxide paste 12 is lapped. The lapping is performed, for example, by rotating a sticky plate made of Teflon resin or the like so as to remove a portion that is higher than the photoresist 10. As a result, as shown in FIG. 6, the paste 12 except for the gas sensitive pattern 9 is removed, and the thickness of the paste 12 is made uniform with the thickness of the photoresist 10. After that, if baking is performed, the photoresist 10 is removed, and the paste 12 is sintered to obtain a gas-sensitive thick film. This state is shown in FIG. After these, Si substrate 2
Is undercut-etched, the SiO2 film 4 remains, and an undercut-etching type gas sensor is obtained. Undercut etching may not be performed.

The aspect ratio and shape limit of the gas sensitive pattern 9 will be described with reference to FIG. The shape accuracy of the gas sensitive pattern 9 is determined by the accuracy of the exposure and development of the photoresist 10, and for example, the shape of about 10 μm width × 10 μm length can be easily obtained. The aspect ratio is given by d / w in the figure, and for example, up to about 3 can be obtained. As a result, for example, 10
μm width × 10 μm length × 30 μm thickness or 60 μm width × 60
A gas sensitive pattern 9 having a length of μm and a thickness of 10 μm can be obtained. The power consumption of the gas sensor is reduced due to the miniaturization of the gas-sensitive pattern, so that a gas sensor with extremely low power consumption can be obtained. The thickness of the gas sensitive pattern 9 greatly affects the characteristics of the gas sensor. Further, variations in thickness cause variations in characteristics. In the embodiment, this thickness is determined based on the thickness of the photoresist 10, and the desired aspect ratio,
For example, a gas sensitive pattern 9 of about 0.01 to 3 can be obtained.

Embodiment 2 A manufacturing method for a thin film gas sensor will be described with reference to FIG. A gas sensitive pattern 9 is obtained in the same manner as in Example 1. Next, as shown in FIG. 9, vacuum deposition, sputtering, CV
The thin film 14 of the gas sensitive material is formed by D or the like. This thin film is
For example, the state of metal Sn in the previous stage or the state of stannic oxide in the final state may be used. When the thin film of the gas sensitive material at the bottom of the pattern 9 is 16 and the thin film at the wall surface of the pattern 9 is 18, the thin film 18 on the wall surface is thinner than other portions. Therefore, if the thickness t of the thin film 14 is sufficiently smaller than the thickness d of the photoresist 10, for example, if it is a fraction or less, the thin film 14 is cut at the wall portion 18 except the photoresist 10. Then, only the thin film 16 at the desired position remains.

For this purpose, the photoresist 10 is removed by, for example, a solvent and ultrasonic vibration. Then, at the same time, the unnecessary portion of the thin film 14 is lifted off, and only the thin film 16 remains. When the ratio between the thickness t of the thin film 16 and the thickness d of the photoresist 10 is smaller, the photoresist 1 is baked.
Even if 0 is removed, the unnecessary portion of the thin film 14 is removed. After forming the thin film 16 only on the gas-sensitive pattern 9, the characteristics of the thin film 16 are controlled by baking or the like, if desired, and the Si substrate 2 is removed by undercut etching.

[0012]

According to the present invention, it is possible to obtain a gas-sensitive pattern which is determined by the precision of the photoresist, make the gas-sensitive pattern fine, and reduce the power consumption of the gas sensor. Further, according to claim 1, the film thickness of the thick film gas sensor can be controlled and made uniform.

[Brief description of drawings]

FIG. 1 is a process chart of an embodiment

FIG. 2 is a process chart of the second embodiment.

FIG. 3 is a cross-sectional view showing a state where the photoresist of Example is applied.

FIG. 4 is a cross-sectional view showing a state after photoresist development of an example.

FIG. 5 is a sectional view showing a state after printing the gas-sensitive paste according to the embodiment.

FIG. 6 is a cross-sectional view showing a state after the gas-sensitive paste lapping of the example.

FIG. 7 is a cross-sectional view showing a state after firing the gas-sensitive paste of the example.

FIG. 8 is a sectional view showing the aspect ratio of the gas-sensitive paste of Example.

FIG. 9 is a cross-sectional view showing a lift-off process in the second embodiment.

[Explanation of symbols]

 2 Si substrate 4 SiO2 film 6 Heater pattern 8 Electrode pattern 9 Gas sensitive pattern 10 Photoresist 12 Gas sensitive paste

Claims (2)

[Claims] 1. A step of applying a photoresist on a substrate to develop the gas-sensitive pattern, a step of applying a paste of a gas-sensitive material to the gas-sensitive pattern and filling the pattern, and a filled gas-sensitive paste. And remove the gas-sensitive paste in the area other than the pattern, and align the thickness of the gas-sensitive paste in the pattern with the photoresist thickness as a reference. A method for manufacturing a gas sensor, the method including the step of forming the gas sensor and the step of removing the photoresist. 2. A step of coating and developing a photoresist on a substrate to form a gas-sensitive pattern, a step of forming a thin film of a gas-sensitive material on the gas-sensitive pattern, and a step of forming a gas-sensitive pattern by removing the photoresist. And a step of removing a thin film of the gas-sensitive material in a portion other than the above.