Etching characteristics and mechanical properties of a-SiC:H thin films

Abstract Due to its chemical inertness after effusing the incorporated hydrogen as well as the oxygen free deposition atmosphere in combination with a deposition temperature 3 /O 2 gas mixture in a plasma enhanced process. By varying important etching parameters as rf power, substrate temperature and total gas pressure, a maximum etch rate of 135 nm/min can be achieved. Further material parameters of the a-SiC:H thin films are determined by load deflection measurements performed at diaphragms. This technique allows to measure interferometically the film stress σ and the Young’s modulus E as a function of annealing time and temperature T a , respectively. Choosing for the latter a temperature range between 450 and 750°C, the film stress changing from −400 to +490 MPa is clearly more affected than the Young’s modulus having a value of 180 GPa (± 5%). At T a =550°C, the intrinsic compressive nature in “as deposited” a-SiC:H layers changes to tensile stress. For devices, operating at temperatures up to 650°C, a post-deposition anneal at 650°C for 240 min is necessary to get thermally stabilized values for σ as well as E . Therefore, micromachined sensors which are in direct contact with aggressive media as well as high temperatures can be well protected by this passivation layer and, hence, increasing their lifetime substantially.