JPH04318450A - Electrostatic capacitance-type humidity sensor - Google Patents

Abstract

PURPOSE:To easily form the humidity-sensitive film of a electrostatic capacitance-type humidity sensor constituted by successively forming a lower electrode, the humidity sensitive film, and an upper electrode on an insulating substrate. CONSTITUTION:After an Mo and Au films are successively formed on a glass substrate by sputtering, a resist pattern is formed by a photolithographical method and a lower electrode 23 is formed by etching. After removing the resist, a negative or positive type photoresist is spin-coated and baked. After baking, a humidity sensitive film 24 is formed by curing the photoresist with ultraviolet rays. Then an upper electrode 25 is formed by vapor-depositing an Au film.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitive humidity sensor. More specifically, the present invention relates to a capacitive humidity sensor with improved environmental resistance such as heat resistance.

0002

2. Description of the Related Art Hitherto, humidity sensors using a polymer film as a moisture-sensitive film include a resistance detection type and a capacitance detection type. Resistance detection types have low reliability of measurement values in low temperature and low humidity areas, while capacitance detection types have poor accuracy in high temperature and high humidity areas, but humidity sensors currently in use are Most of the devices that can measure relative humidity in the range of 0 to 100% are of the capacitive detection type.

[0003] In this capacitive detection type, the surface of a conductive electrode formed on an insulating substrate is generally covered with a polymer film, and a moisture-permeable upper electrode is formed on the polymer moisture-sensitive film. A moisture-sensitive polymer film is sandwiched between this and a lower electrode made of a conductive electrode. The function of the capacitive humidity sensor is based on the principle that the amount of change in dielectric constant that accompanies changes in the water content in the moisture sensitive film due to humidity is detected as the amount of change in capacitance.

Among the capacitance detection type humidity sensors, the following two types of capacitance type humidity sensors have been generally employed. (1) As shown in FIGS. 1(a) to 1(c) of the drawings, a pair of opposing terminal portions 22, 22' are formed on an insulating substrate 21 by applying a sputtering method, a vapor deposition method, and a photolithography method. After forming the shaped lower electrodes 23, 23', the moisture-sensitive film 24 and the upper electrode 25 made of a vapor-deposited film are sequentially stacked and formed (2) Figures 2(a) to (c) of the drawings.
), a lower electrode 34 having a terminal portion 32 and a large electrode portion 33 is formed on an insulating substrate 31, and then a moisture sensitive film 35 is formed over the electrode portion, Further, an upper electrode 36 (or a comb-shaped upper electrode) having a shape symmetrical to that of the lower electrode is arranged so that its electrode portion 37 is located on the moisture sensitive membrane, and its terminal portion 38 is located symmetrically to the terminal portion of the lower electrode. formed like this

The moisture-sensitive films of these capacitive humidity sensors are made of metal oxides such as ZnO and SnO2, or polymeric substances such as cellulose acetate. When forming, patterning is performed using photoresist.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to facilitate the formation of a moisture-sensitive film in a capacitive humidity sensor in which a lower electrode, a moisture-sensitive film, and an upper electrode are sequentially formed on an insulating substrate. It's about getting used to it.

[0007]

[Means for Solving the Problems] The purpose of the present invention is to
In the capacitive humidity sensor having the above configuration, this is achieved by using a humidity sensitive film made of a cured photoresist film as the humidity sensitive film. That is, in the present invention, the moisture-sensitive film is formed using the photoresist itself, which has conventionally been used for patterning when forming the moisture-sensitive film.

[0008] As the insulating substrate, glass, alumina,
Quartz, a silicon wafer whose surface is insulated, etc. are used, and conductors that can be made into thin films, such as Au, Pt, and Al, are used as electrode materials for the upper and lower electrodes having the above-mentioned configuration. This is done by a vapor deposition method, a sputtering method, or the like. Further, the patterning thereof is performed by forming a resist pattern by photolithography and etching.

The moisture-sensitive film formed between the upper electrode and the lower electrode is conventionally formed by spin-coating a coating agent of a material that can be made into a thin film and then pre-baking, and then applying a positive photoresist to the resist after spin-coating, pre-baking, exposure and development. This is done by removing and heat-treating.

[0010] Furthermore, since the upper electrode must be formed on the moisture-sensitive film, it is necessary to mask the terminal part, or to peel off unnecessary parts after laminating the electrode forming material over the entire surface. Photoresist is used.

In the present invention, such a photoresist, such as OMR series (negative type) or OFPR series (positive type) manufactured by Tokyo Ohka Chemical Co., Ltd., is used, and it is spin-coated onto the lower electrode, patterned, and post-baked. After that, the film is further cured by irradiation with ultraviolet rays, thereby forming a moisture-sensitive film with a thickness of about 1 to several μm.

0012

[Effects of the Invention] In a capacitive humidity sensor in which a lower electrode, a moisture-sensitive film, and an upper electrode are sequentially formed on an insulating substrate, the humidity-sensitive film is formed from a cured photoresist film, making it easier to manufacture. Not only is it easier to achieve this, but it also provides faster response due to the thinner film (several μm or less), and the adjustment of the film thickness, or in other words, the response, can be controlled by changing the coating agent concentration, spinner rotation speed, etc. This can be easily done by selecting .

[0013]

EXAMPLES Next, the present invention will be explained with reference to examples.

Example: 500% Mo was deposited on a glass substrate by sputtering.
After continuously forming a film of 2000 Å thick, a resist pattern was formed by photolithography.
Thereafter, etching was performed to form a lower electrode having the shape shown in FIG. 1(a).

After removing this resist, a negative photoresist (OMR-85, viscosity 25c) is applied on the lower electrode.
ps) or positive photoresist (OFPR-80
0, viscosity 25 cps), post-baked (140° C., 30 minutes), and then cured by ultraviolet irradiation to form a moisture-sensitive film having the shape shown in FIG. 1(b).

Furthermore, Au was deposited to form an upper electrode with a thickness of 100 Å in the shape shown in FIG. 1(c).

When measuring the change in capacitance with respect to relative humidity under the following conditions for a capacitive humidity sensor formed with a moisture-sensitive film with a film thickness of 0.8 μm, the graph shown in FIG. 3 is obtained. The results showed a good correlation. Humidity tank: Separate flow precision humidity generator made by Shinei Measuring device: LCR meter made by YHP Conditions: 25°C, 1V, 1KHz applied

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the manufacturing sequence of a conventional capacitive humidity sensor.

FIG. 2 is a perspective view showing the manufacturing order of a conventional capacitive humidity sensor.

FIG. 3 is a graph showing the relationship between relative humidity and capacitance of the capacitive humidity sensor according to the present invention.

[Explanation of symbols]

21, 31 Conductive substrate 23, 34 Lower electrode 24, 35 Moisture sensitive membrane 25, 36 Upper electrode

Claims (1)

[Claims] 1. A capacitive humidity sensor comprising a lower electrode, a moisture sensitive film made of a cured photoresist film, and an upper electrode formed in sequence on an insulating substrate.