洁净硅片在真空中加热时表面状态的XPS谱研究

SURFACE CHARACTERIZATION OF Si(111) WAFERS BAKED IN VACUUM SYSTEM BY XPS

用X射线电子谱（XPS）评价了由改进的RCA方法清洗，又经HF处理的洁净（111）硅片在高真空和超高真空中加低热时的表面状态。实验表时，清洗后的硅片表面沾污中的氧（O）比较少而碳（C）相对多一些，同时存在微量的氟（F）。如果清洗工艺操作得当，可望获得较干净的衬底表面。洁净的硅片在8×10-6Pa的真空中存放12h后，表面吸附的C比O增加得更快。给出了在高低真空中硅片加低热前后表面状态的变化情况，并实时检测在超高真空中加低热时表面状态的XPS谱，同时对实验结果给予分析、讨论。

Surface characterization of HF-dipped immediately after RCA cleaned Si (111) wafers, which were baked out at low-temperature(~250℃) in high or ultrahigh vacuum (UHV) system, was performed by X-ray photoelectron spectroscopy (XPS). XPS surveys demonstrate a little oxygen and small carbon peaks,but negligible fluorine peak. If a cleaning process is in the proper way, a clean Si surface can be obtained. After 12 h of storage in 8×10-6 Pa vacuum, the development of a carbon coverage occurs faster than that of an oxy- gen. When cleaned Si (111) wafers were baked out at low-temperature (255℃) in high vacuum and ultrahigh vacuum system, an oxygen peak is up, carbon down, and flourine almost disappears. These experimental re-sults have been analyzed by a theory of physical and chemical adsorption.