Free-standing CVD diamond wafers for thermal management by d.c. arc jet technology

Abstract

Because of the unfavorable mechanical properties of diamond, the source and type of stresses present must be identified and controlled at every stage of the CVD diamond deposition process in order to develop a high-yield, large-wafer-scale fabrication process. In this paper, we report on the types of defect and stress encountered in free-standing CVD diamond films deposited by d.c. arc jet deposition. Substrate materials and designs, temperature non-uniformity, and process conditions all contribute to the type and magnitude of stresses present in a film. Results of mechanical strength testing by biaxial flexure are presented. Strength sample sets consisted of 20 disks from each diamond wafer. Results from over 50 wafers are summarized. Weibull analysis of strength data is presented, with a description of the effects of thickness and sample orientation. It is shown that by implementing tight process control and through judicious selection of a substrate material, d.c. arc jet technology is capable of producing 175 mm diameter wafers at high yield with uniform properties.