Golden Wafer Study and Application for Critical Dimension Scanning Electron Microscope Stability Control

In this work, we prepared one kind of metallic golden wafer coated with tantalum/tantalum nitride (Ta/TaN) films or single Ta film by either PVD (Physical Vapor Deposition ) process or ALD (Atomic layer deposition) process to alleviate the charge accumulation and mitigate the electrostatic enhanced impurity adsorption. Through this approach, the charging effect on line CD measurement is effectively eliminated. We compared the charging effect among normal wafer, metallic golden wafer, and the evaluated golden wafer’s life time in terms of charging effect prevention by means of a long-term test. Moreover, to extend the lifetime of golden wafer, a rework process was investigated to deoxidize the surface oxidation layer and prevent it from the charging induced long-term performance degradation. For CD-SEM stability control, we designed a daily monitor flow utilizing the golden wafer to ensure and maintain a healthy CDSEM condition for in-line product measurement. Finally, we extended the concept of this metallic golden wafer into other potential metrology related applications such as CD-SEM tool matching and calibration.