Patent ID: 6207534
Filing Date: 2001-03-27
Classification: H01L

Abstract:
A method of forming trenches having two different depths into a silicon substrate in the fabrication of an integrated circuit device comprising:providing a silicon substrate;depositing an oxide layer overlying said silicon substrate;etching through said oxide layer to the top surface of said silicon substrate to form openings for planned first trenches;depositing a polysilicon layer overlying said oxide layer and filling said openings for said planned first trenches;polishing down said polysilicon layer to the top surface of said oxide layer such that said polysilicon layer remains only in said openings of said planned first trenches;thereafter etching through said oxide layer to the top surface of said silicon substrate to form openings for planned second trenches;etching simultaneously said silicon substrate and said polysilicon to complete said first trenches and said second trenches, wherein said etching forms said second trenches deeper than said first trenches and wherein said oxide layer acts as a hard mask; andcompleting the fabrication of the integrated circuit device.