Drastic Improvements of Gate Oxide Reliability by Argon Annealing Compared with Hydrogen Annealing

Abstract

Ar annealing considerably improves the gate oxide reliability of Czochralski (CZ) grown silicon wafers as well as annealing. For both argon and hydrogen annealing at 1200°C for 1 h, the yield of the intrinsic breakdown is drastically improved to a level higher than 90% from the initial value of about 30%. This is established by a significant reduction of near‐surface defects. Ar annealing, similar to annealing, drastically reduces the near‐surface defects, such as oxygen precipitates and grown‐in defects (laser scattering tomography defects and crystal‐originated particles). However, even a small quantity of gas engulfed in the ambient gas suppresses these reductions due to the restraint in oxygen out‐diffusion. Consequently, annealing improves the gate oxide reliability insufficiently. The roughnesses of the wafer surface after Ar and annealings are almost comparable. To reduce the near‐surface defects and improve the gate oxide reliability of CZ silicon wafers, it is essential to avoid the engulfment of into the ambient gas during annealing.