The hole-trapping and electron-trapping characteristics in dry oxides following various chemical cleanings have been studied using the avalanche injection method. The results indicated that hole trap density was almost the same for the chemical cleanings. Electron traps with two capture cross sections, σ, were observed. Electron traps with σ210-17 cm2 were found to be independent of the chemical cleaning, while those with σ410-19 cm2 to depend on the cleaning. Comparison with previous works indicated that electron traps with larger σ were related to Si-OH bonds. The other electron trap showed the increasing trapping rate with increasing the current density injected into oxide. This was explained by trap generation due to electron injection. A correlation between the density of generated electron traps and the amount of Al contamination on surfaces before dry oxidation was observed.

Wet cleaning in actual LSI process is difficult to remove contamination perfectly, because the cleaning condition must be moderate to maintain device characteristics and device texture and because wet cleaning is not so effective for the particles generated during processes such as etching, photo lithography and film formation. Particle reduction depends on particle characteristics, i.e. the sticking force and the chemical structure of the particles. Metallic contamination on wafers, depending on the kind of solutions and the metal concentration in cleaning solutions, degrades TDDB characteristics and recom-bination lifetime. Although the lifetime degradation by the metallic contamination is appreciable, it is much smaller than those caused by damage in etching and in ion implantation.