Patent ID: 7560387

Claim:
A method of opening a hard mask and a silicon-on-insulator (SOI) substrate, the method comprising the steps of: patterning a photoresist over a stack including an anti-reflective coating (ARC) layer, a silicon dioxide (SiO 2 ) based hard mask layer, a silicon nitride pad layer, a silicon dioxide (SiO 2 ) pad layer and the SOI substrate, wherein the SOI substrate includes a silicon-on-insulator (SOI) layer and a buried silicon dioxide (SiO 2 ) layer; and in a single process chamber: opening the ARC layer; etching the silicon dioxide (SiO 2 ) based hard mask layer; etching the silicon nitride pad layer; etching the silicon dioxide (SiO 2 ) pad layer; and etching the SOI substrate, wherein the etch chemistry for etching the SOI substrate includes: using approximately 80-100 standard cubic centimeters per minute (sccm) of difluoromethane (CH 2 F 2 ), approximately 35-45 sccm of tetrafluoromethane (CF 4 ) approximately 25-30 sccm of oxygen (O 2 ) and approximately 180-220 sccm of nitrogen (N 2 ) for the SOI layer; and using approximately 10-30 sccm oxygen (O 2 ) 10-40 sccm hexafluorobutadiene (C 4 F 6 ) and 900-1200 sccm argon (Ar) for the buried silicon dioxide (SiO 2 ) layer.