The role of the OH species in high-k/polycrystalline silicon gate electrode interface reactions

Abstract

In this letter, reactions occurring at the interface between polycrystallinesilicon (poly-Si) and LaSiO x high-dielectric-constant (high-k) insulating layers are characterized using x-ray photoelectron spectroscopy.Dielectrics were formed by sputter deposition of metal on silicon, followed by oxidation at 900 ° C . Amorphous silicon was deposited on top by plasma-enhanced chemical vapor deposition from silane, followed by anneal at 650–1050 ° C . We show that if the dielectric layer is exposed to sufficient water vapor before polysilicon deposition,annealing at 1050 ° C for 10 s is sufficient to completely oxidize ∼25 Å of depositedsilicon. Minimal reaction is observed without deliberate water exposure. This demonstrates the importance of the dielectric surface condition in determining reactivity of high-k/polysilicon interfaces.