JPS59202053A - Manufacture of humidity-sensitive element - Google Patents

Abstract

PURPOSE:To obtain an small and low-cost element by a method wherein a high- molecular humidity sensitive film is formed over a substrate covering an electrode thereon and after the formation of a mask material in a pattern on the humidity sensitive film, the humidity-sensitive film is shaped in a specified pattern on the electrode by oxygen plasma etching. CONSTITUTION:A high-molecular humidity-sensitive film material such as cellulose, polyacrylate and polystylene sulfonate, particularly a polyvinyl alcohol (PVA) is applied on a substrate 1 such as glass and after dried, a humidity-sensitive film 3 is formed covering a pair of comb-shaped electrodes 2a and 2b on the substrate 1 by a heat treatment. Then, a fine pattern 4 of a resist is formed on the film 3 corresponding to the electrode 2. Then, the film 3 is etched by oxygen plasma etching and the resist left is dissolved away to obtain a humidity sensitive film 3' with a fine pattern. Then, an upper electrode 5 is formed on the film 3' and a lead 6 is connected thereto. Thus a small element with a high sensitivity and response is obtained.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a method for manufacturing a moisture-sensitive element that has a moisture-sensitive film made of a polymer film and detects changes in humidity in an atmosphere by changes in impedance. <Prior art> As a moisture-sensitive element whose impedance changes in response to the humidity in the atmosphere, conventionally, sintered bodies of metal oxides such as iron oxide (Fe203 or Fe304) and tin oxide (Sn02) have been used. Or one using metal oxide film, ■ one using hydrophilic polymer membrane, ■ lithium chloride (LiCA)
and those using electrolyte salts such as *No O and J Shee 4 Seishaku Mek Koko Komazuichi 4 Kidney 4 and -444 (27-Kami-δ Tsuru 1
zu)==Ryo=4jijimimeishi, w< (-riho
--- in which conductive particles or fibers such as carbon are dispersed are known. Among these, moisture-sensing elements using metal oxide Idonsai Uso Shichisenzukuri ÷ 1 generally have a wide humidity sensing range, but the resistance value of the element changes exponentially in response to the relative humidity value. . In addition, humidity sensing elements that use electrolyte salts such as lithium chloride have a narrow detectable humidity range, and if the element is left in a high humidity atmosphere for a long time, the electrolyte salts will be eluted or diluted, resulting in significant humidity sensitivity. For reasons such as deterioration, it cannot be used for measurements in high humidity atmospheres. Furthermore, a moisture-sensing element made of conductive particles or fibers dispersed in a hygroscopic resin or the like exhibits a steep resistance change in a high-humidity atmosphere, but lacks sensitivity in a low-humidity atmosphere, making it difficult to detect a wide range of humidity. cannot be used. On the other hand, those using hydrophilic polymer membranes or polymer electrolytes are easy to manufacture, have excellent reproducibility and compatibility, have a wide moisture sensitivity range, have a large resistance change, have high sensitivity, and have a fast moisture response speed. However, as methods for forming these moisture-sensitive films, methods such as tipping and spin coating are usually adopted, or methods such as direct coating are used to form these moisture sensitive films. Pattern formation is not possible. Regarding the wet etching method, since water resistance and solvent resistance of polymeric moisture-sensitive membranes are usually established by methods such as crosslinking, polymerization, or heat treatment, an appropriate etching solution is not available. Therefore, in the past, unnecessary parts of the moisture-sensitive film such as lead connections were removed by melting them with the heat of a soldering iron, or tape was pasted in advance and the moisture-sensitive film was coated, and then the moisture-sensitive film was partially removed with the tape. The pattern was formed using a simple method of not peeling it off. This causes problems such as deterioration of the moisture-sensitive film due to heat and lifting of the moisture-sensitive film at the boundary, and only very large patterns can be formed. Furthermore, there are many problems such as very poor accuracy and reproducibility, and it is extremely difficult to realize a pattern size of one order of magnitude or less using such methods. Screen printing is a method for directly forming patterns, but the viscosity of the printing liquid tends to change, there are many impurities that cause variations, and the accuracy and reproducibility are poor, limiting miniaturization. There are many problems such as 1.For this reason, the screen printing method is not often used as a coach ink method for polymeric moisture-sensitive films.

As mentioned above, it is extremely difficult to perform microfabrication of polymeric moisture-sensitive films using conventional methods, and moisture-sensitive elements in which fine patterns are formed using polymeric moisture-sensitive films have not yet been reported. There wasn't.

On the other hand, in recent years, devices have become smaller and more complex, and FET (field effect transistor) humidity sensors in which a moisture-sensitive material is attached to the gate of the FET are also being developed. Therefore, there is an increasing need for techniques for finely processing moisture-sensitive films.

<Object of the Invention> In view of the above-mentioned current situation, the present invention has been made to accurately produce moisture-sensitive polymer materials.
It is an object of the present invention to provide a method for manufacturing a moisture-sensitive element in which a moisture-sensitive film is micro-processed using a technique for micro-processing it into an arbitrary shape with good reproducibility.

<Example> FIGS. 1(A), (B), (C), (D), and (E) are manufacturing process diagrams of a moisture-sensitive element that is an example of the present invention.

As shown in FIG. 1(A)K, a large number of electrodes (2) for detecting impedance are provided at a predetermined pitch on a substrate made of an insulator such as glass or alumina or a semiconductor such as silicone, Further, as shown in FIG. 1(B), a thin film (3) is formed by coating a solution of a polymeric material by a dipping method, a spin coach ink method, or the like.

The arrangement pitch and width of the electrodes (2) may be less than 1 inch. As the electrode (2), noble metals such as gold and platinum, which are not oxidized even in oxygen plasma, are preferable. Cellulose, polyacrylate, polystyrene sulfonate, polyhinyl alcohol, and others are used as polymeric materials to form 3) on the thin film, but polyhinyl alcohol exhibits particularly good moisture sensitivity properties. .

After dissolving these in a solvent such as water or polyhydric alcohol to an appropriate concentration, a thin film (3) is formed by applying this solution as a coach ink in duplicate.

Next, as shown in FIG. 1(C), after patterning a resist (4) such as a photoresist on the thin film (3), the thin film (3) is etched by exposing it to oxygen plasma in this state. do. At this time, the resist (4) is also etched at the same time, but if the film thickness of the resist (4) is made sufficiently thick, even if the thin film (3) in the areas to which the resist (4) is not attached disappears, the resist (4) will remain etched. 4) also remains. Therefore, by oxygen plasma etching, as shown in Fig. 1 (D
), the thin film (3) is formed by etching according to the pattern of the resist (4). Thin film (3)
The resist (4) remaining above is removed using a stripping solution or a suitable solvent. Through the above steps, a moisture-sensitive element having a moisture-sensitive film (a) in which the thin film (3) is patterned as shown in FIG. 1 is fabricated. As the resist, in addition to the commonly used photoresist, a polymer material such as vinyl acetate polymer formed by a printing method, a metal vapor deposition film, a metal plate mask, a dry film resist, and the like may be used. Regarding the etching conditions using oxygen plasma,
Is it necessary to pay attention to deterioration of the moisture-sensitive film due to an increase in substrate temperature? For example, it is better to reduce the high frequency output as much as possible and use 100% oxygen to reduce the etching time and reduce the rise in substrate temperature, rather than using a mixed gas such as Ar and 02 or N2 and 02. can.

The moisture sensitive element shown in FIG. 1(E) is used by dividing the substrate +l) into individual elements or groups of elements as required.

More fundamental conditions and the like when producing a moisture sensitive element according to the above manufacturing process will be explained using the following specific example.

Specific example 1 Lower electrode backing 7t by mask vapor deposition on a glass substrate
Shape Dk. On the other hand, polyvinyl alcohol powder is dissolved in water, and the solution is coated on the patterned edge electrode-L using a spinner.

After drying and heat treatment, a fine pattern is formed using dry film resist, and oxygen plasma etching is performed. In a cylindrical plasma etching device with a diameter of 250 mm and a length of 300 nm, the oxygen pressure is 0.4 Torr.
+If the high frequency output is set to 150W, etching will be completed in about 20 minutes. When etching is completed, the remaining resist is removed using a solvent such as methylene chloride. Thereafter, an upper electrode pattern is formed on the etched moisture sensitive film by mask evaporation or the like.

Through the above steps, a moisture-sensitive element is manufactured. By connecting the upper electrode and the lower electrode to a detection circuit, it is possible to detect the change in impedance of the moisture-sensitive membrane corresponding to the ambient humidity, and from this, the humidity can be determined. An example of the device is shown in plan view in Figure 2.A lower electrode (2) is placed on a glass substrate (1).
are layered in a planar manner, and a moisture-sensitive film (a) is deposited on top of it. A planar upper electrode (5) is formed on the moisture sensitive membrane (3'), and the upper electrode (5) and the lower electrode (2) are extended from one end thereof and connected to a detection circuit by a lead wire (6). electrically connected to.

Specific Example 2 A metal thin film deposited on a glass substrate is patterned into a pair of opposing comb teeth by photo-etching to form electrodes.

Hereinafter, in the same manner as in Example 1: After polyvinyl alcohol is etched by oxygen plasma etching, the resist is removed using a solvent such as methylene chloride.

An example of a moisture sensitive element obtained by the above manufacturing method is shown in a plan view in FIG. A pair of comb-shaped electrodes (2a) and (2b) are patterned on a glass substrate (1), and a moisture-sensitive film (3) is layered thereon. Comb-shaped electrode (2a), (
2b) are both electrically connected to the detection circuit by a lead wire (6).

<Effect of the invention> As explained in detail above, the method for manufacturing a moisture sensitive element of the present invention includes: ■ Moisture sensing elements can be made extremely small.

(2) It is suitable for wafer processing in which a large number of microelements are produced on a single substrate, and costs can be reduced.

■ Problems such as moisture-sensitive film peeling during manufacturing are solved, and the yield and reliability of device manufacturing are improved.

It has excellent technical effects such as:

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a manufacturing process of a moisture-sensitive element showing one embodiment of the present invention. 2 and 3 are plan views of the moisture sensing device obtained through the manufacturing process shown in FIG. 1, respectively. ■・Substrate 2・Electrode 3・Thin film 3・Moisture sensitive film 4・
・Resist

Claims (1)

[Claims] 1. A method for manufacturing a moisture-sensitive element, which comprises forming a mask material in multiple turns on a moisture-sensitive film made of a polymeric material and subjecting it to oxygen plasma etching.