Free-standing diamond wafers deposited by multi-cathode, direct-current, plasma-assisted chemical vapor deposition

Free-standing diamond wafers, 100 mm in diameter, have been deposited by th e multi-cathode (seven-cathode) direct-current (DC) plasma-assisted chemica l vapor deposition (PACVD) method. The input power was 17.5 kW and the pres sure was 100 torr. The methane concentration in hydrogen was between 3.5% a nd 8% at a constant flow rate of 150 seem, intrinsic tensile stress was con trolled by introducing thermal compressive stress with step-down control of the deposition temperature during diamond deposition. A higher growth rate of 10 mu m h(-1) was obtained by raising the methane concentration to 8%, and the deposited diamond wafer showed good thermal conductivity of 12-14 W cm(-1) K-1. Crack-free, homogeneous and flat diamond wafers with 100 mm di ameter were obtainable. (C) 2000 Elsevier Science S.A. All rights reserved.