Pre-oxidation Silicon Cleaning and its Relation to MOS Reliability and Process-Induced Damage

Abstract

ABSTRACTMaterial and device reliability issues play a critical role in the choice of materials and processing options for ULSI technology and manufacturing. Recently, chemical surface treatments (e.g., fluorine incorporation, nitridation) have been shown to benefit MOSFET gate dielectric reliability. This paper describes the impact of different pre-oxidation chemical surface treatments on the reliability characteristics of MOS structures by using a combination of x-ray irradiation and electrical stress-induced charge injection techniques. X-ray irradiation at 1-2 keV increases oxide-trapped charge and the density of interface states substantially (80-800X), but these changes depend significantly on the chemistry of pre-oxidation cleaning. Furthermore, the specific surface treatment strongly affects subsequent device reliability; MOS degradation is up to 5X lower when fluorine-based surface pre-cleaning is used.