Surface structure chemical transfer method to fabricate low reflectance multi-crystalline Si wafers produced with fixed abrasive machining technology

Abstract

Conventional acidic etching cannot form low reflectance surfaces from multi-crystalline silicon (multi-Si) wafers sawn by fixed abrasive (FXA) machining technology, which makes it difficult to replace the time- and cost-consuming free abrasive (FRA) machining method. In the present work, a nanocrystalline Si (nc-Si) layer is formed by use of the surface structure chemical transfer (SSCT) method, and the layer is used as a starting point of alkaline etching to fabricate low reflectance submicron texture on FXA multi-Si wafers. Although the nc-Si layer cannot be passivated by deposition of a silicon nitride (SiN) layer, the submicron textured surface formed from the nc-Si layer by alkaline etching can effectively be passivated by the SiN layer. Using the developed method, the SiN passivated submicron textured FXA multi-Si wafers possess both high minority carrier lifetime and lower reflectance than that of acidic textured FRA multi-Si wafers. The excellent passivation effect of the SiN layer on the low reflectance textured surface is attributed to the low interface state density of 1.2×1011 cm-2eV-1.