Abstract: According to the present invention, there are provided a method for heat treatment of silicon wafers wherein a silicon wafer is subjected to a heat treatment at a temperature of from 1000° C. to the melting point of silicon in an inert gas atmosphere, and temperature decreasing in the heat treatment is performed in an atmosphere containing 1-60% by volume of hydrogen, a method for heat treatment of silicon wafers under a reducing atmosphere containing hydrogen by using a rapid heating and rapid cooling apparatus, wherein temperature decreasing rate from the maximum temperature in the heat treatment to 700° C. is controlled to be 20° C./sec or less, and a silicon wafer which has a crystal defect density of 1.0×104 defects/cm3 or more in a wafer bulk portion, a crystal defect density of 1.0×104 defects/cm3 or less in a wafer surface layer of a depth of 0.5 &mgr;m from the surface, a crystal defect density of 0.15 defects/cm2 or less on a wafer surface and surface roughness of 1.

Abstract: According to the present invention, there are provided a method for heat treatment of silicon wafers wherein a silicon wafer is subjected to a heat treatment at a temperature of from 1000° C. to the melting point of silicon in an inert gas atmosphere, and temperature decreasing in the heat treatment is performed in an atmosphere containing 1-60% by volume of hydrogen, a method for heat treatment of silicon wafers under a reducing atmosphere containing hydrogen by using a rapid heating and rapid cooling apparatus, wherein temperature decreasing rate from the maximum temperature in the heat treatment to 700° C. is controlled to be 20° C./sec or less, and a silicon wafer which has a crystal defect density of 1.0×104 defects/cm3 or more in a wafer bulk portion, a crystal defect density of 1.0×104 defects/cm3 or less in a wafer surface layer of a depth of 0.5 &mgr;m from the surface, a crystal defect density of 0.15 defects/cm2 or less on a wafer surface and surface roughness of 1.

Abstract: A pellet of ethylene-vinyl acetate copolymer and a perfume are mixed in a mixer, and when the perfume has been impregnated into only the surface layer portion of the pellet, then a fine powder is added and mixed with the perfume-impregnated pellet for the purpose of coating the surface thereof.

Abstract: A slowly releasing perfume composition is obtained by mixing a granulated ethylene-vinyl acetate copolymer and a perfume which contains hydrocarbons and/or esters as an essential fragrant component, at a temperature in the range of about 10.degree. C. to about 50.degree. C.