The new parameter for Si surface characterization and the critical cleaning step

The new parameter for Si surface characterization is introduced to evaluate channel electron mobility and to optimize critical cleaning process which affects channel electron mobility. The new Sm value showed tight correlation with the mobility while the Ra value difference, which is mainly used for this purpose, is within the AFM measurement error. It is found that rinsing at pre-gate cleaning degrades the Sm value. Using single wafer wet cleaning tools, the effect was minimized by short rinse time to 30 seconds.