Patent ID: 8541308

Claim:
A polishing method comprising: providing a semiconductor substrate, wherein the semiconductor substrate includes a polysilicon layer, a silicon nitride layer overlying the polysilicon layer, and a dielectric layer overlying the silicon nitride layer; polishing the dielectric layer until the silicon nitride layer is exposed; and polishing the silicon nitride layer by a fixed abrasive pad having an abrasive thereon until the polysilicon layer is exposed, wherein a polishing slurry used in the polishing process is featured with a PH value ranging from 10.5 to 11, and comprising an anionic surfactant or a zwitterionic surfactant, wherein the dielectric layer comprising silicon dioxide is polished using the polishing slurry, and wherein a removal rate of the polysilicon layer by the polishing slurry is less than about 50 Å/min.