TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Process: The silicon particles are heated at temperature (T1) of 1410degrees C or more which is below the melting point (Tm) of silicon, to obtain rigid hard film such as silicon nitride film. The silicon particles are heated to melt the silicon in the silica nitride film. Then, the silicon is melted and cooled to temperature (T2) of 1383degrees C. The silicon particles are mounted multistory in base plate (102). After, single crystallization silicon nitride film is removed. The damaged layer is formed on the surface-layer of crystalline-silicon particles by polishing the surface of the crystalline-silicon particles. The crystalline-silicon particles are discharged into the crucible containing the melt solution which is in granular form. Then, the granular melt solution is cooled and solidified. Then, the silicon particles are mounted in the upper surface of the base plate. The base plate is installed in the heating apparatus. The silicon particles are heated to temperature below the melting point (Tm) of the silicon in controlled atmosphere containing oxygen gas and nitrogen gas and silicon oxy-nitride film is formed in the surface of the silicon particles. The base plate is cristobalite crystal layer formed in the surface of the substrate which is made of quartz glass. After, single crystallization silicon oxy-nitride film is removed. The temperature gradient of the cooling is 2degrees C/minute-200degrees C/minute. Preferred Conditions: The controlled atmosphere containing nitrogen gas or the controlled atmosphere containing nitrogen gas as main component has pressure of 0.01-0.2 MPa. The controlled atmosphere containing oxygen gas or the controlled atmosphere containing oxygen gas and inert gas has pressure of 0.01-0.2 MPa. Preferred Property: The thickness of the silicon nitride film is 100 nm-10 mu m. Preferred Compositions: The silicon nitride film contains oxygen (10 mol% or more) and metal impurities. The base plate consists of quartz glass, mullite, aluminum oxide, silicon carbide or sapphire. The silicon oxy-nitride film contains metal impurity. The nitrogen gas partial pressure of the controlled atmosphere contains nitrogen (70% or more).