Study of tungsten films deposited by DC sputtering dedicated to integrated heaters

In order to realize cost-effective semiconductor gas sensors, the authors have studied the feasibility of replacing platinum by tungsten for the metallic layer of heaters in a moderate temperature range (25-400 degrees C). Tungsten films were deposited on silicon substrates by direct current magnetron sputtering in argon gas. The deposition of tungsten films was investigated at various working gas pressures to modify the microstructure. The results have shown that low-stressed films showed a good adhesion to silicon substrates. Resistivity values as low as 27 mu Omega cm were obtained for 600 nm films deposited at low argon pressure. After a thermal treatment at 500 degrees C for 30 min., no resistivity variation occurred for films deposited at low argon pressure. Finally, three different structures of tungsten heaters were elaborated by using an optical lithography technique and tested for 300 h at 400 degrees C. (C) 2017 American Vacuum Society.