Patent ID: 7473598
Filing Date: 2009-01-06
Classification: H01L

Abstract:
1. A method for forming a stack capacitor, comprising: providing a substrate with a bottom layer, a BPSG layer, a USG layer and a top layer formed on said substrate; using said top layer as a hard mask and said substrate as a first etching stop layer to perform a dry etching process to form a tapered first trench in said bottom layer, said BPSG layer and said USG layer; removing said top layer; performing a selective wet etching process to partially remove said BPSG layer to form a second trench with a bottle-like profile; depositing conformally a poly-Si layer on the inner wall of said second trench and on the surface of said USG layer; filling said second trench with a sacrificial layer; removing said poly-Si layer unmasked by said sacrificial layer to expose said USG layer; removing said sacrificial layer; using said bottom layer as a second etching stop layer to perform a wet etching process to remove said USG layer and said BPSG layer; performing a static drying process; depositing a dielectric layer; and depositing a conductive material to form said stack capacitor.