High-Pressure Deuterium Annealing for Trap Passivation for a 3-D Integrated Structure

High-pressure deuterium annealing (HPDA) and forming gas annealing (FGA) were applied to monolithically and vertically integrated MOSFETs with a 3-D architecture of one over the other. An overlying poly-Si thin-film transistor (TFT) is positioned over an underlying MOSFET onto a wafer of silicon-on-insulator (SOI). The effects of HPDA and FGA on these double-stacked MOSFETs were quantitatively analyzed by extracting the interface trap density ( <tex-math notation="LaTeX">N_it </tex-math> ) from dc I–V characteristics and border trap density ( <tex-math notation="LaTeX">N_bt </tex-math> ) through low-frequency noise (LFN) measurements. The performance index parameters, such as subthreshold swing (SS) and ON-state current ( <tex-math notation="LaTeX">I_ON </tex-math> ), were also comparatively analyzed. It has been confirmed that, for the superjacent MOSFET, HPDA reduced <tex-math notation="LaTeX">N_it </tex-math> by 250% and <tex-math notation="LaTeX">N_bt </tex-math> by 92% compared to FGA. Additionally, for the subjacent MOSFET, HPDA decreased <tex-math notation="LaTeX">N_it </tex-math> by 15% and <tex-math notation="LaTeX">N_bt </tex-math> by 32% compared to FGA.