The distribution of Cl in LPCVD SiO 2 film deposited by SiH 2 Cl 2 and N 2 O was measured by IMMA. Cl was distributed broadly near the SiO 2 ‐ Si interface even in unannealed film. In thick LPCVD SiO 2 films on Si, surface roughness was observed after thermal oxidation. Cl was markedly piled up near the interface between the thermally grown oxide and the Si substrate. In thin films, surface roughness induced by oxidation was not observed. Cl distribution after oxidation was almost the same as that of unannealed film. The Cl pile‐up is not caused by oxidation, but by the existence of the Si ‐ SiO 2 interface. The cause of surface roughness is attributed to a smaller concentration of oxygen than Cl at the interface.
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Watanabe et al. (1981) studied this question.