DRASTIC IMPROVEMENTS OF GATE OXIDE RELIABILITY BY ARGON ANNEALING COMPARED WITH HYDROGEN ANNEALING

Ar annealing considerably improves the gate oxide reliability of Czock ralski (CZ) grown silicon wafers as well as H-2 annealing. For both ar gon and hydrogen annealing at 1200 degrees 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 signif icant reduction of near-surface defects. Ar annealing, similar to H-2 annealing, drastically reduces the near-surface defects, such as oxyge n precipitates and grown-in defects (laser scattering tomography defec ts and crystal-originated particles). However, even a small quantity o f O-2 gas engulfed in the ambient gas suppresses these reductions due to the restraint in oxygen out-diffusion. Consequently, O-2 annealing improves the gate oxide reliability insufficiently. The roughnesses of the wafer surface after Ar and H-2 annealings are almost comparable. To reduce the near-surface defects and improve the gate oxide reliabil ity of CZ silicon wafers, it is essential to avoid the engulfment of O -2 into the ambient gas during annealing.