JPH04110762A - Electrostatic capacity type humidity sensor - Google Patents

Abstract

PURPOSE:To improve the withstand characteristic against environments by forming a moisture sensitive film from Si oxide or Si nitride. CONSTITUTION:On an electroconductive base board 21 a lower electrode 23 is formed, whereover a moisture sensitive film 24 is formed, and further thereover an upper electrode 25 is formed. Sensor thus formed measures change in the electrostatic capacitance caused by varying relative humidity. The moisture sensitive film 24 is made of Si oxide or Si nitride. Embodying in a thin film in this manner achieves a high response, and the nature inherent in Si oxide or Si nitride should provide improved withstand characteristics against environments such as heat resistance and resistance against attack of organic solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a capacitive humidity sensor. More specifically, the present invention relates to a capacitive humidity sensor that has improved environmental resistance such as heat resistance and organic solvent resistance.

[Prior Art] Conventionally, there are two types of humidity sensors using a polymer film as a moisture-sensitive film: a resistance detection type and a capacitance detection type. The resistance detection type is
The reliability of measured values in low temperature and low humidity areas is low, while capacitive detection types have poor accuracy in high temperature and high humidity areas, but with the humidity sensors currently in use, Most of the devices that can measure the range are of the capacitive detection type.

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 this polymer moisture-sensitive film. It has a structure in which a polymer moisture-sensitive membrane is sandwiched between a lower electrode made of a conductive electrode 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.

By the way, among the capacitance detection type humidity sensors, the following two types are generally employed as capacitance type humidity sensors.

(1) As shown in Figures 2 (a) to (c) of the drawings,
After forming a pair of opposing lower electrodes 23 and 23' having terminal portions 22° and 22' on the insulating substrate 21 by sputtering, vapor deposition, and photophosphorography, the moisture sensitive film 24 and vapor deposition are performed. Upper electrode 2 made of film
(2) As shown in FIGS. 3(a) to 3(c) of the drawings.

After forming a lower electrode 34 having a terminal portion 32 and a large electrode portion 33 on an insulating substrate 31, a moisture sensitive film 35 is formed over the electrode portion, and a moisture sensitive film 35 is formed symmetrically with the lower electrode. A shaped upper electrode 36 (or a comb-shaped upper electrode) is connected so that its electrode part 37 is located on the moisture sensitive membrane and the terminal part 38
The moisture-sensitive film of these capacitive humidity sensors is made of ZnO, S, etc.
It is formed from metal oxides such as nO□ or polymeric substances such as cellulose acetate and polyvinyl alcohol. Moisture-sensitive films formed from such materials have environmental resistance such as heat resistance and organic solvent resistance. There are problems with sexuality.

[Problem to be solved by the invention]

An object of the present invention is to improve the environmental resistance (life) of a capacitive humidity sensor in which a lower electrode, a moisture-sensitive film, and an upper electrode are sequentially formed on an insulating substrate.

[Means to solve the problem]

This object of the present invention is achieved by using a moisture-sensitive film made of silicon oxide or nitride as the humidity-sensitive film in the capacitive humidity sensor having the above structure.

As the insulating substrate, glass, alumina, quartz, a silicon wafer whose surface is insulated, etc. are used, and the electrode materials for the upper and lower electrodes having the above-mentioned configurations include Au, Pt, AΩ, Au, A conductor that can be made into a thin film, such as -, is used, and the film is made into a thin film 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 made of silicon oxide or nitride formed between the upper electrode and the lower electrode is 5in2, Si3
Using a silicon oxide or nitride such as N4 or SiOxNy, a sputtering method, vapor deposition method, etc. is applied while masking so that a moisture-sensitive film is formed only in a predetermined position, and a film thickness of several μm to 1 μm or Forms a moisture-sensitive film less than that.

〔Effect 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 film can be made thinner by forming the moisture-sensitive film from a thin film made of silicon oxide or nitride. In addition, due to the inherent properties of silicon oxides or nitrides, environmental resistance such as heat resistance and organic solvent resistance is improved.

〔Example〕

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

Example: 100% MO was deposited on a glass substrate by sputtering.
After the film was formed to a thickness of 0.05 mm, a resist pattern was formed by photolithography, and then etched to form a lower electrode having the shape shown in FIG. 2(a).

On this lower electrode, 5in2 or Si3N4 was sputtered using a metal masking plate to form a moisture sensitive film with a thickness of 5000 mm each in the shape shown in FIG. 2(b).

Further, Au was deposited to form an upper electrode having a thickness of 700 mm in the shape shown in FIG. 2(C).

When measuring the change in capacitance with respect to relative humidity under the following conditions for the capacitive humidity sensor with the above 5 in 2 or Si, N4 moisture sensitive film formed, the results are shown in the graph in Figure 1. was obtained, and a good correlation was confirmed there.

Humidity tank: Shinei separate flow precision humidity generator Measuring instrument: YHP LCR meter Conditions: 30℃, ]V, 1KHz applied

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between relative humidity and capacity of the capacitive humidity sensor according to the present invention, and FIGS. 2 and 3 show the manufacturing order of the conventional capacitive humidity sensor. FIG. (Explanation of symbols) 21.31... Conductive substrate 23, 34... Lower electrode 24.35... Moisture sensitive membrane 25.36... Upper electrode representative Patent attorney Shikichi 1) Toshio 1st figure M warm friend (%RH) Φdo figure 2 figure 3

Claims (1)

[Claims] 1. A capacitive humidity sensor comprising a lower electrode, a moisture sensitive film made of silicon oxide or nitride, and an upper electrode sequentially formed on an insulating substrate.