Epitaxial silicon is used in a variety of semiconductor devices when a pure silicon layer is required. Epitaxial silicon is generally grown on a substrate and exhibits the same crystal structure as the substrate on which it is grown. Epitaxial silicon layers may have their doping type or concentration controlled independently from the substrate on which the layers are grown. Generally, the substrate on which epitaxial silicon is to be grown must be cleaned prior to the growth to remove impurities and ensure that the epitaxial silicon layer is of a high quality.
One approach to cleaning substrates prior to epitaxial silicon growth is to wash the substrate using hydrofluoric acid and to subsequently hydrogen bake the substrate at high temperatures. However, epitaxial silicon growth on silicon areas cleaned in this manner may exhibit a high degree of unwanted lateral growth. Additionally, dielectric layers that are subsequently exposed to epitaxial silicon growth by chemical vapor deposition may exhibit unwanted epitaxial silicon growth in areas of nucleation in the dielectric layers. Thus, the selectivity of the epitaxial silicon growth process may be low.
Therefore, there remains a need in the art for epitaxial silicon growth methods that do not exhibit a high degree of lateral growth. Additionally, there remains a need in the art for epitaxial silicon growth methods that are selective.