Study of the Amorphous-to-Microcrystalline Transition during Silicon Film Growth at Increased Rates: Extensions of the Evolutionary Phase Diagram

Abstract

ABSTRACTThe microstructural and phase evolution of silicon films (Si:H) prepared by low temperature (200°C) rf plasma-enhanced chemical vapor deposition (PECVD) with hydrogen dilution of silane has been studied using real time spectroscopic ellipsometry (RTSE) and atomic force microscopy (AFM). Both RTSE and AFM support the concept of an evolutionary phase diagram that describes different regimes of bulk layer thickness and H2-dilution ratio R within which predominantly amorphous silicon (a-Si:H) and microcrystalline silicon (μc-Si:H) films are obtained. In this study, the evolutionary phase diagram has been extended to identify four separate growth regimes: (i) a-Si:H with a smooth surface and a stable roughness layer thickness, (ii) a-Si:H with a rougher surface and an unstable roughness layer thickness, (iii) mixed-phase (a+μc)-Si:H, and (iv) fully-coalesced (single-phase) μc-Si:H. Based on this framework, the effect of increased rf power to achieve higher deposition rates in the rf PECVD process was investigated.