Growing Thin Selective Epitaxial Films using Chlorine Etch
Original Publication Date: 2008-Jul-23
Included in the Prior Art Database: 2008-Jul-23
Thin SiGe films grown selectively are being looked at as a channel material for advanced gate stack applications. Conventional embedded SiGe processes are typically operated around 700 C with HCl introduced as an etchant for selectivity purposes, The growth rate for these processes is too fast for thin (<100 A ) films to be grown with acceptable morphology without micropitting and a high degree of roughness, Also a higher Ge % is 30-40 desired for these applications.As a solution the growth temperatures are lowered to ~ 600 C to slow down the growth rate and incorporate more germanium. The problem with this approach is that HCl is not a very effective etchant at temperatures below 700 C and this can lead to serious non selectivity issues leading to growth on dielectric surfaces. In alternative approaches the use of HCl is altogether elminated and the selectivity is totally dependent on nucleation delay on dielectric surfaces. This approach can also be problematic.