Intrinsic Growth Stress in Thermally Grown and Annealed SiO2 Thin Films: Control of Stress-Induced Electronically Active Defects at Si/SiO2 Interfaces

Abstract

ABSTRACTWe find that the density of electronically active defect states, formed close to the Si/SiO2 interface during high temperature oxidation (Tox > 800°C), is proportional to the thickness-averaged stress or strain in the oxide layer. This was established by measuring the midgap interface state density, Dit, and correlating it with: i) a direct measurement of the stress, using a beam deflection technique; and ii) a determination of the oxide strain, using infrared (IR) spectroscopy and a model that relates the frequency of the Si-O bond-stretching vibration to the microscopic strain in the oxide.In addition, the elastic stress at the Si/SiO2 interface has been modified by film deposition onto the SiO2 surface of Si:3N4 film or a variable thickness of an Al gate metal. The additional elastic stress introduced by these depositions did not influence Dit. These observations lead us to conclude that interface traps are generated by “local plastic deformations” that occur during the oxidation process, and are localized in the immediate vicinity of the Si/SiO2 interface.