THE INITIAL GROWTH-MECHANISM OF SILICON-OXIDE BY LIQUID-PHASE DEPOSITION

Selective deposition was observed in the growth of silicon dioxide usi ng liquid-phase deposition process. By adjusting the growth parameters , the key mechanism leading to the observed selective deposition was i dentified. It is found that within the same period of time, a thicker oxide film is grown when the native oxide on the silicon substrate sur face is not removed. This difference in oxide growth is attributed to different surface conditions which affect the initial growth rather th an the subsequent deposition rate. It is proposed that the chemical re action that replaces Si-H surface bonds to Si-OH bonds as well as the formation of some kinds of intermediate product are the rate limiting processes for initial growth. On the other hand, changing the supersat uration level of the hydrofluosilicic acid results in different deposi tion rates although the substrate surfaces are the same. Combining the se results, a critical concentration of hydrofluoric acid which depend s on the substrate surface conditions is determined. As long as the co ncentration of hydrofluoric acid in the solution is smaller than this critical value, the oxide deposition occurs. Otherwise, no oxide can b e grown.