J. Phys. IV France 02 (1991) C2-795-C2-802
LOW-TEMPERATURE SILICON AND GERMANIUM CVD IN ULTRACLEAN ENVIRONMENTJ. MUROTA1, M. KATO1, R. KIRCHER2 and S. ONO1
1 Laboratory for Microelectronics, Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980, Japan
2 Siemens AG, Corp, Research and Development, D-8000 Muenchen 83, Germany
Low-temperature Si and Ge CVD processing was investigated under the cleanest possible reaction environment of SiH4, GeH4 and H2 using an ultraclean hot-wall low-pressure CVD system. Epitaxial growth can be achieved on Si substrates at temperatures as low as 350 and 550°C for Ge and Si, respectively. The deposition rate can be expressed by an equation similar to the Langmuir adsorption isotherm as a function of SiH4 and H2 partial pressure for Si CVD, and only GeH4 partial pressure for Ge CVD with excellent agreement. The substrate orientation dependence of the deposition rate shows that the surface reaction proceeds at adsorption sites composed of dangling bonds on the surface. It is found that the SiH4 decomposition induces nucleation on Si oxide. The nucleation rate is suppressed by the presence of GeH4 and decreases on CVD BPSG compared with SiO2. Therefore, by a proper choice of deposition temperature, SiH4 and GeH4 partial pressure, as well as of the insulating oxide. 500nm-thick selective growth of Si at 850°C and Si-Ge alloy at 550°C could be realized. A perfect selective growth of Ge between Si and SiO2 is obtained. At low surface coverages of GeH4 on Si, facets are formed due to a step-flow dominated growth mechanism. At high surface coverages, plane surfaces are obtained due to dangling bond dependent growth mechanisms.
© EDP Sciences 1991