JP3050652B2 - Gas sensor manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 Gas sensors using thin or thick gas sensing parts are well known. If such a pattern of the gas-sensitive portion is called a gas-sensitive pattern, it is indispensable to miniaturize the gas-sensitive pattern in order to reduce the size of the gas sensor. A commonly used technique for pattern miniaturization is etching. However, stannic oxide, indium oxide, and the like, which are mainly used for gas sensors, are difficult to etch. 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 It is an object of the present invention to provide a method for manufacturing a gas sensor which enables a fine gas-sensitive pattern. Another object of the present invention is to make the thickness of the gas-sensitive thick film uniform.

[0004]

According to the present invention, a step of forming a gas-sensitive pattern by applying and developing a photoresist on a substrate, a step of applying a paste of a gas-sensitive material to the gas-sensitive pattern and filling the pattern, Wrapping the gas-sensitive paste, removing the gas-sensitive paste in areas other than the pattern, and adjusting the thickness of the gas-sensitive paste in the pattern part based on the thickness of the photoresist, and baking the gas-sensitive paste. Forming a gas-sensitive film and removing the photoresist.

The present invention also provides a step of forming a gas-sensitive pattern by coating and developing a photoresist on a substrate, a step of forming a thin film of a gas-sensitive material on the gas-sensitive pattern, and removing the photoresist. Removing a thin film of the gas-sensitive material in a portion other than the gas-sensitive pattern.

[0006]

After filling the photoresist pattern with the gas-sensitive material paste, the pattern is wrapped. Then, the paste of the gas-sensitive material in portions 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 extremely fine, for example, 10 μm × 10 μm.
A pattern of about m can be obtained. Variations in paste thickness result in variations in gas sensor characteristics. However, since the thickness of the paste can be controlled by the thickness of the photoresist, the characteristics of the gas sensor can be made uniform. If the ratio between the thickness of the gas-sensitive pattern and the width or length is called the aspect ratio,
The aspect ratio is determined by the gas-sensitive pattern of the photoresist. This aspect ratio can be, for example, about 3, and an appropriate aspect ratio can be obtained.

In the case of a thin-film gas sensor (the thickness of the gas-sensitive portion is 10 μm or less, more specifically 5 μm or less, and more specifically 1 μm or less), a gas-sensitive 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 by a solvent and ultrasonic vibration or the like. 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, and the gas-sensitive material is removed. A thin film remains only in the pattern. When the thickness of the gas-sensitive material thin film is small and the photoresist thickness is large, even if the photoresist is removed by baking, the gas-sensitive material thin film on the resist and the gas-sensitive material thin film in the pattern are separated. The thin film of the gas-sensitive material can be left only in the pattern.

[0008]

Embodiment 1 FIG. 1 shows a manufacturing process of an embodiment. First, the Si substrate is thermally oxidized or the silica film is sputtered to form S
An iO2 film is formed. Next, an electrode pattern such as Pt and a heater pattern are formed by electroless plating, dry etching after sputtering the entire surface, or the like. Thereafter, 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. After the photoresist 10 is pre-baked, it is exposed and developed to form the gas-sensitive pattern 9. This state is shown in FIG. After the development, post-baking is performed to increase the strength of the photoresist, and stannic oxide paste as a gas-sensitive paste is printed. The type of paste is not limited to stannic oxide, but may be indium oxide or tungsten oxide, or Pt catalyst-added alumina used in a catalytic combustion gas sensor, antimonic acid used in a proton conductor gas sensor, β-alumina solid electrolyte material, etc. Is optional. This state is shown in FIG. Reference numeral 12 denotes a gas-sensitive paste of stannic oxide, which is thicker than the photoresist 10. The printing accuracy is lower than the pattern accuracy of the photoresist, and the tin oxide paste is wider than the gas-sensitive pattern 9. Next, the stannic oxide paste 12 is wrapped. The lapping is performed by rotating a sticky plate such as a Teflon resin, for example, so as to remove a portion which is raised from the photoresist 10. As a result, as shown in FIG. 6, the paste 12 other than the gas-sensitive pattern 9 is removed, and the thickness of the paste 12 is made equal to the thickness of the photoresist 10. Thereafter, 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, the Si substrate 2
Is subjected to undercut etching, the SiO2 film 4 remains, and an undercut etching type gas sensor is obtained. Note that the undercut etching need not be performed.

Referring to FIG. 8, the aspect ratio and shape limit of the gas-sensitive pattern 9 will be described. The precision of the shape of the gas-sensitive pattern 9 is determined by the precision of exposure and development of the photoresist 10, and for example, a pattern of about 10 μm width × 10 μm length can be easily obtained. The aspect ratio is given by d / w in the figure, for example, up to about 3 is 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 of μm length × 10 μm thickness is obtained. Since the power consumption of the gas sensor decreases due to the miniaturization of the gas-sensitive pattern, 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. In addition, variations in thickness cause variations in characteristics. In the embodiment, this thickness is determined based on the thickness of the photoresist 10, and a desired aspect ratio and
For example, about 0.01 to 3 gas-sensitive patterns 9 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 the first embodiment. Next, as shown in FIG. 9, vacuum deposition, sputtering, CV
A thin film 14 of a gas-sensitive material is formed by D or the like. This film is
For example, it may be in a state of metal Sn in a previous stage or in a state of final tin, for example, stannic oxide. Assuming that the thin film of the gas-sensitive material at the bottom of the pattern 9 is 16 and the thin film on 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 less than a fraction, the thin film 14 is cut at the wall portion 18 except for the photoresist 10. Thus, 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 of the thickness t of the thin film 16 to 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 the thin film 16 is formed only on the gas-sensitive pattern 9, the characteristics of the thin film 16 are controlled by baking or the like as desired, and the Si substrate 2 is removed by undercut etching.

[0012]

According to the present invention, a gas-sensitive pattern determined by the accuracy of the photoresist can be obtained, the gas-sensitive pattern can be miniaturized, and the power consumption of the gas sensor can be reduced. In the case of the first aspect, the thickness of the thick-film gas sensor can be controlled and made uniform.

[Brief description of the drawings]

FIG. 1 is a process diagram of an embodiment.

FIG. 2 is a process diagram of a second embodiment.

FIG. 3 is a cross-sectional view showing a state where the photoresist of the embodiment 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 of a gas-sensitive paste according to the embodiment.

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

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

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

FIG. 9 is a cross-sectional view showing a lift-off step 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)

(57) [Claims] A step of forming a gas-sensitive pattern by applying and developing a photoresist on a substrate; a step of applying a gas-sensitive material paste to the gas-sensitive pattern to fill the pattern; and a step of filling the filled gas-sensitive paste. To remove the gas-sensitive paste in areas other than the pattern, and to adjust the thickness of the gas-sensitive paste in the pattern area based on the thickness of the photoresist. Forming a gas sensor and removing the photoresist. A step of forming a gas-sensitive pattern by coating and developing a photoresist on a substrate; a step of forming a thin film of a gas-sensitive material on the gas-sensitive pattern; and removing the photoresist to form a gas-sensitive pattern. Removing the thin film of the gas-sensitive material in a portion other than the above.