Hot-Electron Trapping and Generic Reliability of p + Polysilicon/SiO2/Si Structures for Fine-Line CMOS Technology

Abstract

The generic reliability of p+ polysilicon/SiO2/Si structure has been investigated using avalanche injection method on MOS capacitors. Hot-electron trapping in p+ polysilicon/SiO2/Si capacitors with 250Å and 500Å thick oxides was compared with n+ polysilicon/SiO2/Si capacitors. For the identical injection conditions, p+ polysilicon gate capacitors show larger threshold voltage shifts compared to n+ polysilicon gate capacitors with the same thickness. These threshold voltage shifts were significantly reduced after the standard low temperature H2 anneal. A correlation of hot-electron trapping before and after the hydrogen anneal indicates that boron atoms themselves do not act as electron traps in SiO2, but the presence of boron in SiO2 enhances the water-related electron traps. A model is proposed and supported by Infrared measurements on TEOS and BTEOS films.