SI SELECTIVE EPITAXIAL-GROWTH USING CL-2 PULSED MOLECULAR-FLOW METHOD

We have investigated a new method of Si selective epitaxial growth (SE G). This is a Cl-2 pulsed molecular flow method in which a Si substrat e is alternately irradiated with Si2H6 and Cl-2 in an ultra-high vacuu m chemical vapor deposition (UHV-CVD) chamber. The result of the Si et ching by Cl-2 reveals that the Cl-2 irradiation has no influence on th e Si epitaxial layers at temperatures low enough that the faceting pla ne does not develop. On the other hand, the Cl-2 irradiation has a lar ge effect on selectivity improvement, when the Si2H6 irradiation is ar ranged in short periods. This method has realized the selective growth almost indefinitely by the reduction of the Si2H6 irradiation period even at the low temperature. This suggests that for selectivity improv ement it is very important that the individual adsorbed Si atoms be re moved by Cl-2 in the initial stage of the Si2H6 irradiation because Si atoms cannot be removed at low temperature after they form silicon cl usters. We have demonstrated the use of this method in forming a Si-ba sed photodetector and showed that a trench about 2 mu m deep can be fi lled with selective epitaxial layers having small faceting planes. (C) 1998 Elsevier Science S.A. All rights reserved.