JPH02239175A - Formation of thin film - Google Patents

Abstract

PURPOSE:To obtain a thin film having satisfactory adhesive property by previously forming a glassy coating layer on a smooth ceramic substrate, firing the layer, forming a desired thin film on the layer and carrying out heat treatment. CONSTITUTION:An Al2O3 substrate is used as a ceramic substrate 1. A glassy coating soln. is sprayed on the Al2O3 substrate and dried to form a glassy coating layer 3. This layer 3 is melt-bonded to the substrate by firing in vacuum or in gaseous hydrogen or argon. A film of a desired thickness is then formed by sputtering and wet or dry-etched in the form of a desired pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of forming a thin film. More specifically, the present invention relates to a method of manufacturing a thin resistor film for a thin high-temperature heater such as a small heater for high-temperature heating or a heater for an electron gun that uses a temperature of about 1000°C.

[Conventional technology]

Conventionally, flat plate heaters have been proposed, for example, in Japanese Patent Application Laid-Open No. 55-2464.
As described in Japanese Patent No. 6, it is manufactured using a so-called thick film circuit forming technique such as screen printing.

The conventional flat plate heater is shown in FIG. Figure 4 is a schematic cross-sectional view showing an electron tube cathode device using a conventional thin high-temperature heater. An insulating layer 0, a cathode material layer C, a cathode lead layer (14), and a base metal layer 6 are formed in this order.When manufacturing this flat heater, first a ceramic substrate (K)) is formed. A raw material is prepared, and a resistor (heating element) layer 01) having a desired pattern is formed on a sheet by a printing technique such as an extrusion method or a casting method in which the material is passed between rolls. This resistor (heating element) layer 01) is formed by screen printing a paste containing a heater material and a firing aid on the substrate (g). After screen printing, a baking treatment is performed at a high temperature (1000 to 2000° C.) to form a flat plate heater.

In this method, the adhesion between the resistor layer 01) and the ceramic substrate (g) is high, and since a high temperature treatment process is involved during manufacturing, the change in resistance over time is small when the heater is used at a temperature below this treatment temperature. High-temperature, long-term stability as a heater can be expected. However, the pattern accuracy obtained by screen printing is low, and the heating element @01
1 Thickness control 1 [I (thinness) is difficult, so there is a problem that power consumption is large, and there is also a problem that there is a large variation in resistance between heaters due to the number of heaters provided on the board. There is also. Therefore, the development of film forming methods for resistors and the like using PVD and CVD has been progressing as a method for forming patterns with high precision.

5a and 5b show a method of manufacturing a flat thin heater using a conventional thin film forming method. In other words, a heater resistor (heating element) gao is uniformly formed on a smooth ceramic substrate (2), a desired heater pattern is formed by etching, etc., and a lead wire Q4 is bonded to this. A flat plate thin heater was realized.

(Problems to be Solved by the Invention) However, flat plate thin heaters using the conventional film forming method as described above have a problem in that the film peels off from the substrate while applying voltage to the lead wires and using it as a heater. This is mainly due to the fact that the adhesion of the resistor film to the substrate is originally weak, that the internal stress balance changes due to the thermal history during use, and that the thermal expansion coefficients of the substrate and film are different. As a result, flat thin heaters manufactured using the conventional film-forming method suffer from changes in heat capacity due to peeling, fluctuations in resistance, and disconnections within the resistor pattern, making the heater unstable. It has the disadvantage of lacking long-term reliability.

The present invention has been made in order to solve the problems of the conventional methods, and it is an object of the present invention to provide a method for forming a thin film with high adhesive strength that does not cause peeling during use. The purpose of this research is to provide a method for forming a thin, high-temperature heater with high reliability.

[Means to solve the problem]

For example, the iill! of the present invention can be applied to the manufacture of resistors for thin high-temperature heaters. The formation method involves applying a glassy coating layer on a smooth insulating substrate such as a ceramic substrate, firing it, forming the desired thin film such as a resistor for a heater, and heat-treating it at high temperatures. This method aims to achieve the above objective.

That is, in the present invention, a coating layer made of glass is formed on a cleaned insulating substrate, and after firing the coating layer,
The present invention relates to a method for forming a thin film, which comprises forming a desired thin film thereon and subjecting it to heat treatment.

(Function) In the present invention, the fired glassy layer is fused between an insulating substrate such as a ceramic substrate and a thin film such as a resistor film, and acts as a seal coat to enhance adhesion. In the final heat treatment process, the internal stress of the film is relaxed and recrystallization is promoted, which improves adhesion and stabilizes resistance.

〔Example〕

An embodiment of the present invention will be described below based on the drawings. FIG. 1 is a diagram showing the manufacturing process and cross-sectional structure of a thin high-temperature heater according to an embodiment of the present invention. In Figure 1, (1) is a ceramic substrate (insulating substrate), (2 is a resistor film for a heater, (3) is a glassy coating layer, (
4) is a lead wire.

It is desirable for each material to satisfy, for example, the following requirements.

It is desirable for the substrate (1) to have good thermal conductivity, a coefficient of thermal expansion close to that of the resistor film, a good insulator, no dielectric breakdown at high temperatures, and smoothness. Specific examples of such materials include M N,
Examples include M203.

It is desirable for the resistor film (2) to have a low vapor pressure in a high temperature range and to have stable electrical characteristics in a high temperature range. Specific examples of such materials include HO, Pt, Ta
, Tic, TiN, etc.

It is desirable for the glassy coating layer (3) to have low diffusion at high temperatures and to have a softening point or melting point higher than the operating temperature. A specific example of such a material is a coating layer made of stable glass with a high softening point and a high melting point, such as Si02 and #203. For example, for S i O2, the softening point is 1710°C (crystal)
, melting point 1470℃ (crystal), melting point 2 for AI203
030°C. Furthermore, the material may contain substances such as CaO and Y203 that are scattered to the outside during firing.

It is desirable that the lead wire (4) has the same characteristics as the resistor film and the same diffusion coefficient as the resistor film, and is most preferably made of the same material as the resistor film.

Here, in view of the above conditions, A is used as a ceramic substrate.
A method for manufacturing a thin high-temperature heater using j2Qt (alumina, sapphire), forming a resistor film by a sputtering method as a resistor film, and applying a vitreous coating liquid containing S102 as a main component as an example of a vitreous protective coating layer. Let's talk about.

The above-mentioned glass coating solution is sprayed onto the Aj203 substrate and dried to form a vitreous coating layer. Next, it is baked for 5 to 10 minutes in vacuum or in hydrogen or argon to fuse it to the substrate. The processing temperature at this time varies depending on the composition of the coating liquid, but is approximately 800 to 1400°C. Next, use the spatter method to obtain the desired thickness (several ~
10I! Y! ) to form a uniform film. Thereafter, it is etched into a desired pattern using a wet or dry method. For example, if a wet method is used, etching is performed in the next step.

Resist coating → Mask setting → Exposure → Resist removal → W etching (for example, K 3 [Fe(CM)@]+Nal solution) →
A high-temperature heat treatment at 800 to 1000° C. is performed before or after the resist removal pattern is created, and finally the lead wire is joined to a desired location by a method such as resistance welding.

As the coating liquid for forming the vitreous coating layer, a solution containing a so-called vitreous oxide may be used. As specific examples of such coating liquids, A, B.
The compositions (weight %) of three types of coating liquids of C are shown.

These are examples of glass-type ceramic coating materials that are commercially available.

The composition (% by weight) of the material called frit in Table 1 is shown in Table 2, which is a so-called glassy oxide.

Table 2 This vitreous material dissolves a small amount of metal oxide formed on the resistor film during use as a heater, fills the gaps between metals, and acts as a seal coat, providing close contact with both the resistor film and the ceramic substrate. It also has excellent adhesive properties, contributing to high adhesion between the material and the substrate. In addition, since it is glassy, it has high electrical insulation properties and can be considered as part of the board.
It does not interfere with its function as a high temperature heater.

Fig. 1 shows an example of coating a glassy layer on the front surface of the substrate, but as shown in Figs. 2a to 20, a mask (5) is used when coating the glassy layer (3), and a After forming a glassy layer only in the portion where the pattern of the resistor liI (2) is formed (see Figure 2a), if the resistor film (2) is formed (see Figure 2b), the glassy layer (see Figure 2b) is formed.
3), the adhesive force is large on the substrate (1), and the adhesive force is small on the substrate (1), so that the pattern accuracy of the resistor 111 (2) when forming the pattern by etching becomes higher.

Furthermore, as shown in FIG. 3, it is also possible to process both sides of the ceramic substrate over a large area. Also in Figure 3, (1) is an insulating substrate, (2) is a resistor film, {
3} is a glassy coating layer, and (4) is a lead wire.

In addition, in the example, a method of forming a glassy coating layer by applying a coating liquid was explained, but other methods such as preparing glassy targets 1 to 1 and forming a film by a sputtering method, etc.
, It goes without saying that a glassy coating layer can be formed using the CVD method.

For glassy compositions, it does not have to be a composite composition as shown in Table 2, but may be a single composition such as s r o2, N203, etc. For example, if the board is #203, if you coat it with +Aj203, it can be considered as part of the board, so if you prepare a board as thin as the coating layer in advance, it will be easier to design dimensions such as heat capacity. Moreover, it also has the advantage of not having to take into account the effects of impurities and diffusion.

In addition, in the embodiment, a method of forming a resistor film (thin film) by forming a W film by a sputtering method was explained, but it is also possible to use so-called PVD methods such as electron beam evaporation, laser PVD method, and ion blating, WF6, W film, etc. (CO)s, IA
It goes without saying that CIajj and the like can be formed using the CvD method or the like.

The same applies when a film other than W, such as HO, is formed.

〔Effect of the invention〕

As explained above, according to the present invention, when forming a desired thin film such as a resistor film for a thin high-temperature heater, a glassy coating layer is provided on a smooth ceramic substrate in advance, and this is fired. Since the thin film, such as a resistor film for a heater, is subsequently formed and heat-treated at a high temperature, a thin film with good adhesion can be obtained.

In particular, in the area where the resistor film is formed, it is possible to form a resistor film with high adhesion that prevents the resistor from peeling off when the heater is used, resulting in the provision of a thin, high-temperature heater with high long-term reliability. play.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the cross-sectional structure and manufacturing process of a thin high-temperature heater obtained by an embodiment of the method of the present invention;
2a to 2C are schematic diagrams showing the manufacturing process of a thin high-temperature heater according to another embodiment of the method of the present invention, and FIG. 3 is a cross-section of a thin high-temperature heater obtained by yet another embodiment of the method of the present invention. FIG. 4 is a schematic cross-sectional view showing an electron tube cathode device using a conventional thin high-temperature heater, and FIGS. 5a to 5d are schematic diagrams showing the manufacturing process of a thin high-temperature heater using a conventional thin film forming method. It is. (Main symbols in the drawings) (1): Ceramic substrate (insulating substrate) (z: Resistance film (thin film)) (3): Glass coating layer (4): Lead wire agent Masu Iwa, Nihon University, Yuzai Tsusai 20 Figure 2. Resistor film 4: Lead wires 3 and 4

Claims (1)

[Claims] (1) A method for forming a thin film, which comprises forming a coating layer made of glass on a cleaned insulating substrate, baking it, forming a desired thin film thereon, and subjecting it to heat treatment.