Stress relief of tetrahedral amorphous carbon films by post-deposition thermal annealing

The stress relief of tetrahedral amorphous carbon (ta-C) films by post-deposition thermal annealing was investigated. The films were subjected to rapid thermal annealing (RTA) for 2 min and conventional furnace annealing (CFA) for 30 min. In both cases, the films were annealed in vacuum with argon (4 x 10-2Torr) at successive higher temperatures ranging from 500 to 800°C. It was found that annealing by RTA achieved a greater stress reduction and a smaller change in the I(D)/I(G) ratio (obtained from the Raman signal of the films) than annealing by CFA. For a ta-C film subjected to 700°C RTA, the stress decreases substantially by ~ 90%, as compared to the ~ 80% achieved by CFA. The I(D)/I(G) ratio of the ta-C film subjected to 700°C RTA is 0.23 as compared to 0.27 for CFA. This suggests that a higher stress relief of ta-C films can be better achieved by a shorter annealing time without sacrificing much degradation in their diamond-like properties. Subsequent deposition and annealing steps to deposit thicker films were carried out. Films up to 0.8 μm thick with diamond-like properties have been successfully grown.