Annealing of Ionizing Radiation Induced Defects in Insulated Gate Field Effect Transistors Using Elevated Pressure

Abstract

Intrinsic and extrinsic bulk defects (generated using Al‐Kα x‐rays) were characterized using optically assisted electron injection into the gate insulator of completed insulated gate field effect transistors. Following labeling of neutral defects or annihilation of charged defects, the resulting threshold voltage shift due to charge collection at defect sites was used as a measure of the density of such bulk defects. The present study focuses on the effectiveness of reducing extrinsic defect densities (fixed positive charge and large neutral electron traps) as a function of gate insulator thickness using various high pressure anneals, and on the effect of annealing on defect centroid. A unique high pressure annealing system is described. The system is a specially modified commercial tool and has its own dedicated gas supply for the high pressure process. Extensive modifications to the annealing system and to the gas supply system are described including the addition of safety interlocks and a thermal conductivity gas analyzer. Radiation‐induced defect densities decreased following all anneals, including high pressure pure argon. However, hydrogen‐containing atmospheres were far superior, with the effectiveness of an anneal directly related to the partial pressure of hydrogen employed. (The partial pressure of hydrogen is equal to the hydrogen concentration multiplied by the total pressure.) For the first time, dry oxide thicknesses in the range of 6 to 50 nm, grown in 0 and 4.5% at 1000°C, have been examined.