Rugged surface polycrystalline silicon film formed by rapid thermal chemical vapor deposition for dynamic random access memory stacked capacitor application

Abstract

Polycrystalline silicon films with a rugged surface (rugged poly-Si), deposited by a single-wafer rapid thermal chemical vapor deposition (RTCVD) system suitable for 12 inch wafer fabrication, are studied and the films have been successfully applied to bottom storage electrodes for stacked capacitors in dynamic random access memory cells. Our data show that the rugged poly-Si is actually formed by the nucleation generation on the amorphous silicon surface and subsequent crystalline growth during the annealing step following deposition. We also determined that a wide temperature window exists for the formation of rugged poly-Si (i.e., +/- 15 degrees C) using RTCVD, which is wider than that using low pressure chemical vapor deposition (LPCVD) (i.e., +/-3 degrees C) and ultra high vacuum chemical vapor deposition (UHVCVD) (i.e., +/-10 degrees C). Stacked capacitors fabricated using rugged poly-Si and thin silicon oxide/silicon nitride dielectric film show that for a rugged poly-Si storage electrode with a 60 nm top-layer and 645 degrees C annealing, an effective surface area of approximately 2.9 times that of a conventional poly-Si film electrode is obtained.