Influence of atomic hydrogen on the growth reactions of amorphous boron films in a low-pressure B2H6+He+H2 plasma

Abstract

The activation energy (E) of the growth reactions of boron films in plasma-assisted chemical vapor deposition from B2H6+He+H2 at a pressure of 300 Pa was measured at a range of substrate temperature from 750 to 1200 K. It was found that the E decreases continuously from 1.83 to 0.54 kcal/mol and then increases up to 4.97 kcal/mol with the increase of partial pressure of atomic hydrogen ([H]). The continuous change of E is supposed to be due to the transition of the dominant rate determining growth reaction, which is accompanied with the change of the composition of adsorbed layer on a film surface. The variation of E as a function of [H] can be explained with a kinetic model proposed here, in which the E of the growth reaction through BH3 is assigned to 1.83 kcal/mol, that through BH2 to 0.54 kcal/mol, and E of migration of BH2 on the film surface covered with hydrogen is related to be 4.97 kcal/mol.