Patent ID: 6849557

Claim:
A process for forming a contact opening to a semiconductor material, said process comprising: forming an undoped silicon dioxide layer over a layer of semiconductor material; selecting an etch process that is selective to undoped silicon dioxide and to silicon; forming a doped silicon dioxide layer over said undoped silicon dioxide layer; and selectively removing by said etch process at a total etch pressure in the range from about 1 millitorr to about 400 millitorr and by using an etchant selected from the group consisting of C 2 F 6 , C 3 F 8 , C 4 F 10 , CH 2 F 2 , C 2 HF 5 , CH 3 F, and combinations thereof, a portion of said doped silicon dioxide layer at a material removal rate that is higher for doped silicon dioxide than for undoped silicon dioxide or for said layer of semiconductor material to form an opening extending to a contact surface on said layer of semiconductor material.