| 摘要 |
PURPOSE:To prevent decomposition of a thin film circuit with impurities, by cleaning the surface of a ceramic substrate so that the amount of the impurities is less than 1.0 mug/cm<2>. CONSTITUTION:The total amount of impurities of Na, K, Cl, F and SO3, which are present on the surface of a ceramic substrate 1, on which at least a conductive thin film 3 is formed, is made to be less than 1.0/ g/cm<2> per unit surface area. Such a ceramic substrate 1 for a semiconductor device is used. As the ceramic substrate 1, any of Al2O3, AlN, SiC and Si3N4 is desirable, or the mixed body of at least two kinds of them is desirable. The method for cleaning the surface of the ceramic substrate so that the amount of the impurities on the surface is less than 1.0mug/cm<2> is as follows. The ceramic substrate is immersed in pure water at high temperature or the substrate is boiled in the pure water. This method is simple and effective. Even in the semiconductor device that is packaged at a high density, increase in circuit resistance due to the corrosion of the thin film circuit, heating of circuits and the like do not occur, and the highly reliable ceramic substrate is obtained.
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