Residual stress in thin films PECVD depositions: A review

The paper presents solutions for residual stress control in thin films deposition on plasma enhanced chemical vapor depositions (PECVD) reactors and some MEMS applications. The residual stress induced in the thin films is an important factor in the fabrication of thin and free standing MEMS structure such as membranes or cantilevers fabricated using surface or bulk micromachining. The main layers analyzed are: amorphous silicon, amorphous silicon carbide and amorphous silicon nitride. The main parameters analyzed are the temperature of the deposition process, pressure, gas composition, as well as the value of the power and the power mode (high frequency - 13.56 MHz or low frequency - 400 KHz. Due to annealing effect, the temperature can decrease the compressive value of the stress. The RF frequency mode presents a major influence of residual stress: in low frequency mode a relatively high compressive stress is achieved due to ion bombardment and, as a result, densification of the layer is achieved.