Synthesis of High-Quality Ultra-Thin Gate Oxides for ULSI Applications

Abstract

A critical challenge in achieving ultra-large-scale-integration (ULSI) is growing ultra-thin oxides with low defect (D 0 ) and interface trap (Q it ) densities and generating a planar stress-free silicon/oxide (Si-SiO 2 ) interface. This paper describes the fabrication of a thin, multilayered, stacked SiO 2 structure with such characteristics. The dramatic improvement in the quality of these stacked oxides has been achieved through a novel synthesis of a three-step process that involves growing, depositing, and growing SiO 2 layers on silicon substrates by thermal oxidation, chemical vapor deposition, and densification/oxidation, respectively. These oxides have an ideal combination of low defect and interface trap densities. The Si-SiO 2 interface generated during the synthesis is structurally superior. Oxides of this high quality are needed — with shallow junctions and fine-line geometries — to produce scaled-down devices that can be integrated into ULSI circuits with multilevel interconnects.