Atomic Hydrogen Exposure to Enable High-Quality Low-Temperature SiO2 with Excellent pMOS NBTI Reliability Compatible with 3D Sequential Tier Stacking

Abstract

Fabrication of stacked CMOS tiers in a 3D sequential integration requires development of low thermal budget process modules. High-quality SiO2 interfacial layer (IL), obtained up to now only by high-temperature (>= 850 degrees C) oxidation or exposure, is crucial for pMOS NBTI reliability. In unannealed IL's grown at reduced temperatures, we show that unrelaxed interface strain induces high defect densities, with physics-based NBTI modeling suggesting excessive hydroxyl-E' defect formation due to Si-O bond stretch. Based on ab-initio theoretical insights, we demonstrate an atomic hydrogen treatment to passivate SiO2 defects at low temperatures (100-300 degrees C), which is shown to be vastly more effective than high pressure molecular hydrogen exposure, and to yield an SiO2 quality and reliability surpassing a 900 degrees C oxide.