Patent ID: 6696103
Filing Date: 2004-02-24
Classification: C04B,H01L

Abstract:
A method for producing aluminium nitride ceramic having a dense smooth surface layer possessing a surface roughness Ra of lower than 0.3 &mgr;m and possessing no defect larger than 25 &mgr;m on its surface, comprising(i) providing a sintered article of aluminium nitride and then applying at least one layer of a paste of oxide glass that contains no Na, no K, no Rb, and no Pb for the surface layer directly onto a surface of the sintered article of aluminium nitride and sintering said paste, or (ii) providing a preform of aluminium nitride which is not yet sintered and then applying at least one layer of a paste of oxide glass that contains no Na, no K, no Rb, and no Pb for said surface layer directly onto a surface of the preform and sintering the paste and the preform, wherein the paste is applied such that the final surface layer has a thickness between 10 &mgr;m and 250 &mgr;m after sintering, thereby producing an aluminium nitride ceramic having a dense smooth surface layer possessing a surface roughness Ra of lower than 0.3 &mgr;m and possessing no defect larger than 25 &mgr;m on its surface, and wherein the sintered aluminium nitride (1) comprises aluminate and aluminium oxide-nitride in which the oxygen content after an amount of oxygen converted to aluminates is deducted from the total oxygen in the sintered article of aluminium nitride is less than 2% by weight, (2) the carbon content in the sintered aluminium nitride substrate is in the range of 0.005 to 0.5% by weight, and (3) the boron content in the sintered aluminium nitride substrate is less than 1% by weight.