REAL-TIME ULTRAVIOLET ELLIPSOMETRY MONITORING OF GATE PATTERNING IN AHIGH-DENSITY PLASMA

The use of in situ diagnostic tools, allowing real-time control during plasma-processing steps, may become a key issue in designing robust p rocesses and reducing costs for the next generations of integrated cir cuits. Real-time ellipsometry is capable of monitoring the growth and the etching of various materials, but its use has generally been restr icted to unpatterned areas. In this study, we focus on the monitoring of polysilicon and poly SiGe gate patterning using real-time ellipsome try in the ultraviolet. It is shown that the same characteristic signa ture is obtained at the end of the polysilicon etching in unpatterned and low pattern-density areas. The analysis of this signature reveals the presence of a perturbed layer at the surface of polysilicon during etching. In addition, whatever the nature of the etched materials, th e mask layout, and the underlying topography, ellipsometric real-time traces can be used for process end pointing and control. (C) 1997 Amer ican Vacuum Society.