JPS60112683A - Surface smoothing method for ceramic substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to surface treatment of ceramics, and more particularly to a surface smoothing method for reducing surface roughness of a ceramic substrate for an integrated circuit module. Integrated circuit modules are manufactured by patterning and etching a smooth substrate, and ceramic substrates are widely used along with silicon substrates and glass substrates. Ceramic substrates are manufactured by molding fine inorganic crystals and then sintering them, so their surfaces are rough and have large irregularities compared to silicon substrates, glass substrates, etc. With the increase in the degree of integration of integrated circuit modules, the surface roughness of the substrate becomes a problem as the width of the pattern becomes smaller, and there is a limit to the degree of integration when using a ceramic substrate with a large surface roughness. Mechanical polishing methods are generally used to smooth the surface of ceramic substrates, but it is extremely difficult to mechanically polish extremely thin ceramic substrates, which are aggregates of highly hard inorganic crystals. Since grain defects and cracks along grain boundaries are likely to occur, the yield is poor and the product is extremely expensive.

As a method for smoothing the surface of a ceramic substrate in place of the mechanical polishing method, JP-A-55-75981 discloses a method of coating the surface of a ceramic substrate with a liquid coating composition containing at least one non-polymer silicon compound. A method of drying and heating and baking has been proposed. However, since the coating composition exemplified in this method contains an unsaturated organosilicon compound having an ethylene bond in order to impart film-forming properties, gelation tends to occur and the coating composition Poor stability. Furthermore, coating compositions that do not contain unsaturated organosilicon compounds have better film-forming properties than those that contain them. Furthermore, unsaturated silicon compounds having ethylene bonds are expensive and difficult to obtain.

Its purpose is to.

As a result of intensive research to achieve the above object, the present inventors have found that an organic solvent solution containing oligomers as a main component obtained by reacting alkoxysilanes with water has excellent coating film forming properties and is extremely stable. The present invention was completed by paying attention to this fact.

The present invention is characterized in that an organic solvent solution containing an oligomer obtained by reacting alkoxysilanes with water is applied as a coating composition to the surface of a ceramic substrate to form a coating film, and then heated and baked. This is a method for smoothing the surface of a ceramic substrate.

In the present invention, alkoxysilanes are expressed by the following general formula (
1) A compound represented by the formula % (1) (where R represents the same or different type of monovalent hydrocarbon group having 1 to 18 carbon atoms), which can be reacted with water. It easily forms oligomers or polyR-mers having Si, R-o+si, and o'+ bonds. As the alkoxylan, tetramethoxysilane, γtraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, dimethoxyjethoxysilane, dimethoxydiynepropoxysilane,
Jetoxydibutoxysilane, diisopropoxydibutoxysilane, tetradiethylhexoxysilane, etc. are listed, and tetramethoxylan, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, etc. are produced in one place. , is preferably used because it is easily available.

In the present invention, the degree of polymerization obtained by reacting one or more of the above alkoxysilanes with water is 2 to 2.
0. An organic solvent solution containing 1 to 15% by weight of an oligomer having a molecular weight of 500 to 10Q000 in terms of Si oxide is used as a coating composition. Alkoxysilane monomers are undesirable because they absorb moisture in the air and easily polymerize, making the coating composition cloudy and poor stability.Also, polymers with a degree of polymerization of 20 are not suitable for organic solvents. It is not preferred because it is difficult to dissolve and even if it does dissolve, the viscosity of the coating composition is too high.

If the concentration of the oligomer in the coating composition is too low in terms of Si oxide, the thickness of the S1 oxide film formed when it is applied to a ceramic substrate to form a coating film and heated and baked will decrease. This is undesirable because it increases the number of repetitions of coating and heating and baking the coating composition for smoothing the ceramic substrate. This is not preferable because it sometimes tends to cause scratches. The oligomer production reaction may be carried out by directly reacting alkoxysilanes with water in an organic solvent, or in the presence of an alcohol and an organic acid such as acetic acid.

Any organic solvent can be used as long as it can dissolve the oligomer, such as aliphatic hydrocarbons that are liquid at room temperature such as octane, aromatic hydrocarbons such as benzene, toluene, and xylene. ,) Halogenated hydrocarbons such as dichlorethylene, perchlorethylene, and chlorobenzene, lower alcohols such as methanol, ethanol, isopropanol, and n-butanol, esters such as methyl acetate and ethyl acetate, acetylacetone, benzoylacetone, etc. Examples include β-diketo acids, ketonic acids such as acetoacetic acid and globionylbutyric acid, and lower alkyl esters thereof.

These organic solvents may be used alone or as a mixed solvent of two or more. Furthermore, alkali metal oxides, phosphorus compounds, etc. can be added to the coating composition as desired as glass-forming agents.

In the present invention, the coating composition is applied to the surface of the ceramic substrate to form a coating film, and then heated and baked at a temperature of 150°C or higher to form a metal oxide coating with a smooth surface on the ceramic substrate. It is formed. Depending on the surface roughness of the ceramic substrate, if the surface roughness of the ceramic substrate cannot be eliminated by applying the coating composition and heating and baking it once, it can be smoothed by repeating the process multiple times. can. If the firing temperature is too low, the substituents or hydroxyl groups of the oligomer may not be completely eliminated and may remain in the oxide film, which is not preferable. On the other hand, if it is extremely high, the oxide film will crystallize or the crystals will grow and become granular, which is not preferable. The preferred heating and firing temperature is usually 3
00℃~ioo.

It is ℃. There are no particular restrictions on the method of applying the coating composition to the ceramic substrate, but a dipping and pulling-up method is preferably used since it provides a coating film of uniform thickness.

The attached FIG. 1 shows the measurement results of the surface roughness of a ceramic substrate treated by the method of the present invention in comparison with an untreated ceramic substrate and a commercially available glass substrate. As is clear from FIG. 1, by repeating the treatment according to the method of the present invention, the ceramic substrate is smoothed and has a smoothness close to that of a glass substrate.

The present invention provides an economical and industrial surface smoothing method for ceramic substrates using an inexpensive and stable coating composition, and its industrial significance is extremely important.

EXAMPLES Below, the present invention will be explained in more detail with reference to Examples. However, the scope of the present invention is not limited in any way by the following examples.

Example 1 Preparation of coating composition; Tetramethoxysilane: 126f to ethanol: 42
75'1 Acetic acid: 199f and Hydrochloric acid: 0.1f were added, stirred and reacted at a temperature of 70°C for 10 hours, and a coating composition containing oligomers with a molecular weight of L000 to IQOOOO at a concentration of 5x in terms of SiO□ was obtained. was prepared.

Smoothing treatment of ceramic substrate: A commercially available alumina substrate of 100 × 150 × 2 pieces was immersed in the coating composition prepared above, pulled up by 25 cm at a speed of 1 minute, and then held at a temperature of 150 ° C. for 10 minutes. It dried to form a coating film. 2 and then held at a temperature of 500° C. for 30 minutes to form a 5i02 film. Two more times
The coating composition was applied and fired under the same conditions as above to form a SiO□ film. Alumina substrate and 5i
02 For each coating, use a thin film step measuring device (manufactured by Kosaka Institute: E).
T-10 type), stylus: 0.5 μmR1 load:
The surface roughness was measured under the conditions of 20 mg/measurement speed of 4 μm/sec. The measurement results of the surface roughness are shown in FIG. 1 together with the surface roughness of a commercially available glass substrate. As is clear from the attached FIG. 1, the surface becomes smoother as the number of times the coating composition is applied and heated and baked increases.

Example 2 Various coating compositions were prepared, and a commercially available alumina substrate was smoothed using the coating compositions.

The preparation conditions of the coating composition, the smoothing treatment conditions of the alumina substrate, and the measurement results of the surface roughness are shown in Table 1 together with Example 1.

In Table 1, the surface roughness represents the step difference between the maximum peak and the maximum pot in μm.

(Hereinafter &>U) Example 3 Stability of nucleated composition: The coating composition prepared in Example 1 was placed in a sealed container and left at room temperature for a long time, and the viscosity change at 20 ° C. It was measured.

The measurement results are shown in Table 2.

Table 2 Also, when alumina substrate was smoothed in the same manner as in Example 1 using these coating compositions left for a long time, a smooth surface with the same surface roughness as in Example 1 was obtained. I was able to do that.

[Brief explanation of drawings]

Figure 1. Curve representing the surface roughness of the substrate measured in Example 1. Axis magnification: 5QOOOO times Horizontal axis magnification: aooo times Code used: A, glass substrate B; ceramic substrate C: substrate D after first smoothing treatment. :Substrate E after second smoothing treatment:Substrate after third smoothing treatment Patent applicant Nippon Soda Co., Ltd. Agent (6286) Haruyuki Ito (7125) Yoshimi Yokoyama

Claims (1)

[Claims] 1. An organic solvent solution containing an oligomer obtained by reacting alkoxysilanes with water is applied as a coating composition to the surface of a ceramic substrate to form a coating film, and then heated and baked. A method 2 for smoothing the surface of a ceramic substrate characterized by 1 to 15% by weight, method 4 according to claim 1, and method according to claim 1, wherein the heating and firing temperature of the ceramic substrate on which the coating film of the coating composition is formed is 150° C. or higher. 5. The method according to claim 1, in which applying the coating composition to the surface of the ceramic substrate and heating and baking are repeated two or more times.