Dummy Poly Removal Impact Factors and Improvement in Hkmg Last Process

Abstract

Logic Technology and Development Center SMIC 201312For 20/16nm HK-last and MG-last process, Dummy poly is removed by Wet process. This paper studies the factors impacting the dummy poly removal process, and presents some models to explain the impacting factors. Implant process is one of main factors influencing dummy poly removal capability because the differences of implant ions and doping amount into dummy poly induce difference of poly removal rate by wet process. We also study poly surface single clean, multiple clean and thermal process. Based on the model, we plan N-type doping poly and P-type doping poly with different ion doping amounts on blank wafer and 20nm structure wafers to evaluate dummy poly removal. We find dummy poly removal rate is different between N-type doping poly and P-type doping poly, and receive different dummy poly removal trend by ion amount on N-type doping poly and P-type doping poly. The model can help to improve dummy poly removal process control.

Dummy Poly Gate Removal Process Optimization with Pulsing Plasma Application

“…Both capping layer surface interface and more capping layer loss could lead to Vt shift [11]. Due to the presence of the first gate metal, the second dummy gate removal process cannot use the stronger wet process to clean byproduct/polymer [12], Hence, PET step at the end of the etching has to be adopted to remove the byproduct/polymer. The study found that by the presence of the PET step, the threshold voltage can be improved 18% (Fig 5).…”