Effect of PECVD conditions on mechanical stress of silicon films


In the work, silicon films were obtained from SiH4 by plasma-enhanced chemical vapors deposition. The influence of deposition temperature (200 – 650°C) and gas mixture pressure (500 – 2000 mTorr, Ar/SiH4) on the mechanical stresses in the films were studied by stylus profilometry and curvature method. Mechanical stresses in films with thickness changing from 270 nm to 1.93 μm are in the range of −750 to +250 MPa. The deposition rates were 7 – 46 nm/min irrespective of temperature at 500 mTorr. Temperature dependences had inflection close to 450°C. Low-stressed (tensile and compressive) and stress-free films can be formed and qualified for solar cells fabrication, based on textured silicon, glass or flexible substrates as well as for micro- and nanomechanics, particularly relatively thick films of 1 – 2 μm, obtained at 2000 mTorr and rates about of 50 nm/min.