The effect of surface treatments and growth conditions on electrical characteristics of thick (> 50 nm) gate oxides

In contrast to submicrometer geometry; metal oxide semiconductor (MOS) devi ces which feature ultrathin gate oxides, power MOS field effect transistor (FETs) require gate oxides in the thickness regime from 50 to 70 nm. In thi s experiment, the effect of preoxidation surface treatments and thermal gro wth conditions on electrical integrity of thick gate oxides is investigated and compared with the effect on thin oxides (<15 nm). It is demonstrated t hat the response is relatively independent of oxide thickness when the same . temperature of oxidation is used to grow thick and thin oxides. However, when thick gate oxides of the same thickness are grown at different tempera tures, the effect of metallic contaminants, namely Fe and Al, plays a decis ive role in determining oxide characteristics. In the case of metal-free su rfaces (HF/HCl last clean) better oxide integrity in terms of both E-bd and Q(bd) is obtained at high temperatures of oxidation (1000 and 1175<degrees >C). However, in the case of starting Si surfaces contaminated with metalli c impurities. (ammonia hydrogen peroxide mixture-last clean), the benefits of using a high temperature of oxidation are seen only in terms of Ebd char acteristics while Q(bd) characteristics are significantly deteriorated as c ompared with oxides. grown at 900 degreesC. (C) 2001 The Electrochemical So ciety.