JP2962337B2 - Moisture sensitive element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moisture-sensitive element. More specifically, the present invention relates to a moisture-sensitive element in which the surface of a conductive interdigital electrode formed on an insulating substrate is covered with a moisture-sensitive plasma polymerized film.

[0002]

2. Description of the Related Art A moisture-sensitive element in which the surface of a conductive interdigital electrode formed on an insulating substrate is covered with various moisture-sensitive plasma polymerized films has been previously proposed by the present applicant. As the plasma polymerized film, a chlorine-containing polymer, preferably a plasma polymerized film of vinylidene chloride (JP-A-61-290351),
Plasma polymerized film of bis (trimethylsilyl) acetamide
(No. 62-49250), a mixture plasma polymerization film of a nitrogen-containing organic silicon compound and a halogenated hydrocarbon (No. 62-282255), a mixture plasma polymerization of a nitrogen-containing organic silicon compound and a halogenated silane Film (No. 62-255860), a mixture of an organic amine and a halogenated hydrocarbon or a halogenated silane Plasma polymerized film (No. 62-261946) or a nitrogen-containing organosilicon plasma polymerized film formed of an alkyl halide (Japanese Patent No. 62-80543).

[0003] Some of these plasma polymerized films have quaternary ammonium salts formed in the film, and therefore exhibit excellent moisture-sensitive properties. It has a function similar to that of the humidity sensor.

By the way, although a polymer electrolyte type humidity sensor can be used even in a high humidity region, it is common that salt in a membrane easily flows out when dew condensation or immersion in water for a long time. There are problems. For this reason, instruction manuals for commercially available polymer electrolyte type humidity sensors include:
It is often described to avoid condensation or use in water.

The present inventors have developed a plasma polymerized membrane having a function similar to that of the polymer electrolyte type as described above,
In particular, for a moisture-sensitive element using a quaternary ammonium salt-containing plasma polymerized film as a humidity sensor, its water resistance is improved,
As a result of various investigations so that the function can be sufficiently exerted even in a dew condensation state or in water, it was found that the above object can be achieved by further covering the moisture-sensitive plasma polymerized film with another specific plasma polymerized film. (Japanese Unexamined Patent Publication No. 63-177050
Publication).

[0006]

However, a moisture-sensing element which is not normally used in a high-temperature environment is also stable in a temperature range of about -30 to 85 ° C., for example, in consideration of use in a vehicle cabin. Sex is being demanded.

An object of the present invention is to provide a moisture-sensitive element which exhibits stability even when left at 100 ° C. in response to such a demand.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a non-silicon-based photoresist baking treatment film by coating a moisture-sensitive plasma polymerized film covering the surface of a conductive interdigital electrode formed on an insulating substrate. This is achieved by a moisture-sensitive element coated with.

As the insulating substrate, glass, quartz, alumina or the like is generally used. An insulating film formed by oxidizing the surface of a silicon substrate proposed by the present applicant (Japanese Patent Application Laid-Open No. 61-281958) Gazette) can also be used.

In forming a conductive interdigital electrode on these insulating substrates, first, an electrode made of a corrosion-resistant metal such as stainless steel, Hastelloy C, Inconel, Monel, or gold, or an electrode such as silver or aluminum is formed on the insulating substrate. A thin metal film having a thickness of about 0.1 to 0.5 μm is formed from a metal forming material by sputtering, ion plating, or the like, and then a photoresist pattern is formed thereon.

For example, in the case of aluminum, the formation of a photoresist pattern on the thus formed metal thin film for forming an electrode is performed by applying a well-known photolithographic process. That is, a photoresist coating is performed on a metal thin film, a glass dry plate on which a negative or positive image of a pattern of a comb-shaped electrode is baked is superposed, and baking and development by light irradiation are performed.
Thereafter, wet chemical etching is performed, and the etching solution is phosphoric acid-sulfuric acid-chromic anhydride-water (weight ratio 65:
15: 5: 15) Mixed solution, BHF (hydrofluoric acid), ferric chloride aqueous solution,
Nitric acid, a mixed solution of phosphoric acid and nitric acid, or the like is used.

The surface of the conductive comb-shaped electrode formed on the insulating substrate is covered with the above-mentioned plasma polymerized film having various moisture-sensitive properties. As the monomer used for forming the moisture-sensitive plasma polymerized film, various monomers are used as described above. Preferably, a mixture of a nitrogen-containing organic silicon compound and a halogenated silane, an organic amine or a nitrogen-containing heterocyclic compound is used. A mixture of a compound and a halogenated hydrocarbon or a halogenated silane is used.

As the nitrogen-containing organosilicon compound, for example,
A compound represented by the following general formula is used. R_ThreeSi-NR_Two  R_TwoN-SiR_Two−NR_Two  (R_TwoN)_Three--SiR (where R is a hydrogen atom, a methyl group, an ethyl group, a vinyl group
Or an acetylene group, and R_TwoOr R_ThreeAre the same or
Are different R groups that have at least two hydrogen
(Including groups other than children)

Specific examples of such compounds include, for example, trimethylsilyldimethylamine, triethylsilazane, hexamethyldisilazane, hexamethylcyclotrisilazane, bis (dimethylamino) methylvinylsilane,
Bis (trimethylsilyl) acetamide, tris (dimethylamino) silane, tris (dimethylamino) methylsilane, tris (methylamino) methylsilane, tris (methylamino) ethylsilane, N, N-dimethylamino-N'-methylamino-N'- Ethylaminosilane and the like, preferably trimethylsilyldimethylamine or bis
(Dimethylamino) methylvinylsilane or bis (dimethylamino) dimethylsilane is used.

The organic amine is an aliphatic or aromatic tertiary amine, preferably substituted with an alkyl group.
Secondary amines such as n-butylamine, secondary butylamine, isopropylamine, dimethylethylamine, diethylamine, (substituted) monoamines such as dimethylallylamine, and N, N-dimethyl-
(Substituted) diamines such as 1,3-propanediamine and N, N, N ', N'-tetramethylethylenediamine, and cycloalkyl-substituted monoamines such as pentamethyleneimine and hexamethyleneimine; N, N'-dimethylpiperazine And aromatic amines such as aniline and its derivatives.

As the nitrogen-containing heterocyclic compound, for example, pyridine, 2-methylpyridine, 4-vinylpyridine, 2-methylpyrazine, dimethylpyrazole and the like are used.

As the halogenated hydrocarbon, preferably, an alkyl halide is used, and the halogen substituent may be one or more. Specifically, methylene bromide, methane bromide, tribromide methane, ethylene bromide, ethylene dibromide, propane bromide, propane dibromide, butane bromide, butane dibromide, methylene chloride, bromide Methylene chloride,
Ethyl iodide and the like are used. Further, the hydrocarbon group to be halogenated may be a chain unsaturated bond or an aromatic nucleus.

The halogenated silane is represented by the general formula SiX₁X_Two
X_ThreeX_Four(Where X₁~ X_FourIs halogen atom, hydrogen atom, lower
Alkenyl group or lower alkenyl group or lower alkyl
And one to three of these are halogen atoms.
Used), preferably a lower
Kill substituted halogenated silanes are used. Such haloge
Some examples of fluorinated silanes are as follows:
You. CH_ThreeSiCl_Three  CH_ThreeSiH_TwoBr, CH_ThreeSiHBr_Two  (CH_Three)_TwoSiBr_Two

[0019] Plasma polymerization is in accordance with the shape and plasma generation method of the plasma polymerization apparatus, several nitrogen-containing organic silicon compound, an organic amine or a nitrogen-containing heterocyclic compounds
At a pressure of mTorr to several Torr, and a halogenated hydrocarbon or halogenated silane is also used at a pressure of several mTorr to several Torr, a discharge power of several watts is applied to these mixtures.
It is performed by supplying power of ~ 100W.

Specifically, for example, when the organic amine is used and the discharge output is 20 W, the organic amine is about
A halogenated hydrocarbon or halogenated silane is used in a ratio of about 0.01 to 0.1 Torr to 0.04 to 0.2 Torr.
If the proportion of the halogenated hydrocarbon or the halogenated silane is too small, the halogen content in the plasma-polymerized film decreases and the moisture-sensitive properties deteriorate, while if the proportion is too large,
Since the nitrogen content in the plasma polymerized film is relatively reduced and the polymerized film is cured, the moisture sensitivity is also lowered.

In the present invention, the moisture-sensitive plasma-polymerized film is further covered with a non-silicon-based photoresist baking film. As the non-silicon type photoresist, for example, an aromatic bisamide type photoresist which is a negative type resist, a quinone diazide type photoresist which is a positive type resist, or the like is used. Commercially available products can be used as they are, the former being Tokyo Oka products OMR-83 and OMR-85, Kodak KMER products, and the latter being Tokyo Oka products OFPR-2, OFPR-800 and Shipley. Products include RC300, S2400, and S9800.

For forming a protective film using these, after spin-coating using a spinner, a heat treatment corresponding to a usual post-bake is generally performed at about 130 to 140 ° C. for about 20 to about 140 ° C.
This is performed by applying for about 30 minutes, whereby a protective film having a thickness of about 0.8 to 2 μm is formed on the moisture-sensitive plasma polymerized film.

The moisture sensitive element is manufactured by soldering or attaching a lead wire with a silver paste or the like to a portion of the extraction electrode which is not covered with the moisture sensitive film and the protective film.

[0024]

As described above, the protective film for covering the plasma polymerized film as the moisture sensitive film is required not to adversely affect the excellent responsiveness characteristic of the moisture sensitive element provided with such a moisture sensitive film. Therefore, it is required that the film thickness is about 1 μm and the environment resistance is good.

In the present invention, a baking treatment of a non-silicon-based photoresist is performed in place of the conventionally proposed protective film made of a nitrogen-free organic silicon compound or a hydrocarbon polymerized film of a hydrocarbon or a baking treatment film of a silicon coating agent. By using the film as a protective film, it is possible to ensure the stability under high-temperature conditions without impairing the characteristics of the moisture-sensitive element having the moisture-sensitive plasma polymerized film.

[0026]

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

Example 1 A glass plate was used as an insulating substrate, and a comb-shaped electrode having an electrode width of 100 μm and an electrode interval of 50 μm was formed on the surface of the glass plate by a lift-off method generally used as a patterning method of a platinum electrode.

In this lift-off method, a positive resist is applied to the glass plate surface using a spin coater, prebaked at 85 ° C. for 30 minutes, and then subjected to close contact exposure with ultraviolet light using a mask. Develop to form an inverted pattern of the comb electrode,
Comb-shaped electrodes were formed by sequentially depositing 50 nm of chromium and 150 nm of platinum, and finally immersing in acetone to remove the remaining resist.

The surface of the comb-shaped electrode on the glass plate thus formed was covered with a plasma polymerized film of N, N, N ', N'-tetramethylethylenediamine and methylene bromide. Plasma polymerization uses N, N, N ', N' at a flow rate of 3.1 SCCM.
-Using a gas mixture of tetramethylethylenediamine and methylene bromide with a flow rate of 1.4 SCCM, pressure 0.08 Toor, output 60 W,
The test was performed under a discharge condition for 10 minutes.

A non-silicon-based photoresist (resist OFPR-800, a product of Tokyo Ohka) is spin-coated on the thus formed plasma-polymerized moisture-sensitive film using a spinner.
A baking treatment was performed at 30 ° C. for 20 minutes to form a protective film having a thickness of 1.2 μm.

Example 2 In Example 1, another non-silicon based photoresist was used.
(Tokyo Oka Product Resist OMR-85) is used and the film thickness is 1.2μm
Was formed.

Comparative Example 1 In Example 1, a protective film having a thickness of 5.0 μm was formed by using a silicon coating agent (trade silicone product SE9140) instead of the non-silicon photoresist.

Comparative Example 2 In Example 1, a methyltrimethoxysilane plasma-polymerized film (film thickness) as a protective film was formed on the plasma-polymerized moisture-sensitive film.
0.6 μm). This plasma polymerization protective film was formed by forming a plasma polymerization moisture-sensitive film, reducing the pressure in the reactor to 10 ^-4 Torr while keeping it in the plasma reactor, and adding methyltrimethoxysilane to the reactor by 0.06 Torr. The introduction was performed at a pressure of Torr and plasma polymerization was performed at a discharge power of 60 W for 10 minutes.

Comparative Example 3 A baking treatment film of a silicon coating agent (SE9140) was further formed on the plasma-polymerized protective film (thickness: 0.6 μm) of Comparative Example 2.
(A film thickness of 5.0 μm).

Comparative Example 4 In Example 1, no protective film was formed.

The humidity-sensitive devices obtained in each of the above Examples and Comparative Examples were allowed to stand for 1,500 hours under indoor conditions, 100 ° C. or 60 ° C.-90% RH, respectively. It was converted into a change in relative humidity and evaluated. The results obtained are shown in the following table. Table leaving condition 100 ℃ 60 ℃ -90% RH indoor 10 Example 1 0-1% RH 2% RH 2-3% RH 〃2 〃 〃 例 Comparative Example 1 2-3% RH> 10% RH 5% RH 〃2 1-2% RH 3-5% RH 2-3% RH 〜3 5% RH> 10% RH 5% RH 〃40-1% RH 〃3-5% RH

Claims (1)

(57) [Claims] 1. A moisture-sensitive element comprising a moisture-sensitive plasma-polymerized film covering the surface of a conductive interdigital electrode formed on an insulating substrate and covered with a non-silicon-based photoresist baking film.