LOW TEMPERATURE SELECTIVE EPITAXY OF SILICON GERMANIUM ALLOYS EMPLOYING CYCLIC DEPOSIT AND ETCH

摘要

Cyclic deposit and etch (CDE) selective epitaxial growth employs an etch chemistry employing a combination of hydrogen chloride and a germanium-containing gas to provide selective deposition of a silicon germanium alloy at temperatures lower than 625° C. High strain epitaxial silicon germanium alloys having a germanium concentration greater than 35 atomic percent in a temperature range between 400° C. and 550° C. A high order silane having a formula of SinH2n+2, in which n is an integer greater than 3, in combination with a germanium-containing precursor gas is employed to deposit the silicon germanium alloy with thickness uniformity and at a high deposition rate during each deposition step in this temperature range. Presence of the germanium-containing gas in the etch chemistry enhances the etch rate of the deposited silicon germanium alloy material during the etch step.