Low-temperature silicon cleaning via hydrogen passivation and conditions for epitaxy

In low-temperature epitaxial Si deposition methods such as molecular beam epitaxy (MBE), pre-epitaxial substrate preparation usually incorporates a high temperature (≳800°C) step. Elimination of this step is essential to wider applicability of these epitaxial methods. We show that Si(100) wafers exposed to HF vapors in a laboratory ambience are bulk terminated and that such termination is stable in air for several tens of minutes, and in vacuum for several hours. It is possible to obtain good epitaxy, as determined by surface diffraction and transistor characteristics, provided epitaxy is commenced on these bulk-terminated surfaces. We also give evidence that under certain conditions, bulk-terminated surfaces are maintained in low-temperature epitaxy using the method of ultrahigh vacuum chemical vapor deposition.