Stability of Sputtered Hf-Silicate Films in Poly Si/Hf-Silicate Gate Stack Under the Chemical Vapor Deposition of Poly Si and by Annealing

Abstract

We investigated the effects of SiH₄ gas on the surface of Hf-silicate films during the deposition of polycrystalline (poly) Si films and the thermal stability of sputtered Hf-silicate films in poly Si/Hf-silicate structure by using High Resolution Transmission Electron Microscopy (HR-TEM) and X-ray Photoelectron Spectroscopy (XPS). Hf-silicate films were deposited by using DC-magnetron sputtering with Hf target and Si target and poly Si films were deposited at 600℃ by using Low Pressure Chemical Vapor Deposition (LPCVD) with SiH₄ gas. After poly Si film deposition at 600℃, Hf-silicide layer was observed between poly Si and Hf-silicate films due to the reaction between active SiH₄ gas and Hf-silicate films. After annealing at 900℃, Hf silicide, formed during the deposition of poly Si, changed to Hf-silicate and the phase separation of the silicate was not observed. In addition, the Hf-silicate films remain amorphous phase.