Investigation of Wafer Warpage Induced by Multi-layer Films

Oxide/poly-Si films were repeatedly grown on one side of 300 mm silicon wafers to induce bending, the extent of which was quantified by warp and bow changes. Bending was affected by crystal properties, wafer shape, and local stress, as well as by oxide layer thickness and heat treatment temperature, being less pronounced for wafers with high boron and oxygen impurity concentrations and those with low initial warp, especially, in the case of negative (concave shape) initial bow. Additionally, we investigated the effect of wire-saw cut bending on site flatness and demonstrated that local area damage such as soft laser marking induced a sudden deterioration of edge flatness.