Glass-ceramics for the coating and bonding of silicon semiconductor material

Abstract

Workers in the field of microminiature solid state electronics are interested in the possible use of glass-ceramics for the coating and bonding of silicon semiconductor material in the fabrication of integrated circuit devices. The glass-ceramics must be able to withstand temperatures of 1100–1200°C and should be reasonably well matched in expansion to silicon. It has been shown that glass-ceramics of the ZnO-Al 2O 3-SiO 2 type containing proportions of CaO, BaO or B 2O 3 give materials which are matched in linear thermal expansion characteristics to silicon and which can be applied to pre-oxidized silicon at temperatures in the region of 1200°C to give smooth, adherent coatings on the silicon, the coatings being refractory at temperatures in excess of 1100°C. The glass-ceramics can also be used to bond together pieces of silicon using similar firing schedules to those used to provide the coatings on silicon. By suitable choice of the firing conditions and control of the thickness of the silicon oxide interlayer, the attack by the glass-ceramic on the underlying silicon can be reduced to a negligible amount. The glass-ceramics of the types examined have been shown to have high volume resistivities (greater than 10 8 ω cm at 500°C) and can resist the environmental conditions likely to be encountered in diffusion processes.