Stress reduction for hard amorphous hydrogenated carbon thin films deposited by the self-bias method

Hard amorphous hydrogenated carbon (a-C:H) thin films were deposited by the r.f. (13.56 MHz) self-bias method using 2-methyl-propane as the source gas. To achieve stress reduction, we used the periodic plasma deposition technique: repeated cycles of alternating 5 s of deposition (plasma on) with 180 s of cooling (plasma off). Substrate temperature changes during the plasma deposition were monitored by a fluorescent/ optical thermosensor. We investigated the film deposition rate, density, and internal stress as functions of the deposition temperature.

We found a linear relationship between the internal stress of a-C:H films and the deposition temperature over the range of 0 to 150 °C. The increase in internal film stress from 0.48 to 1.5 GPa, respectively, over this deposition temperature range is the result of the increase in deposition temperature. Within the range of deposition temperature and r.f. power parameters studied, the deposition temperature appeared to play a more significant role in determining the intrinsic film stress than the r.f. power.