Study and Improvement on the Defects of PREB Process
This paper describes that in metal gate(e.g.AL)semiconductor chip manufacture,it is necessary to add a special process to remove Poly and metal refill.PREB(Photo Resistor Etch Back)is a key step in the process,the main purpose isto remove the poly hardmask before etching poly.Due to the height difference between the hard mask of NMOS and PMOS,and the different thickness of the photoresistance in different graphic density areas,the process window is tight,and the production maintenance is difficult.It is easy to suffer a variety of defects including Poly Residue,which seriously affect the final yield of the product.This paper classifies the defects,explores their formation mechanism,and puts forward monitoring methods to reduce the incidence of defects.At the same time,try to optimize the process conditions and improve the overall process window.
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