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US 5,965,035 AGranted
Self aligned contact etch using difluoromethane and trifluoromethane
AssigneeApplied Materials, Inc.
InventorsRaymond Hung, Jian Ding, Joseph P. Caulfield, Gerald Z. Yin
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Abstract
An oxide etch process that is highly selective to nitride, thereby being beneficial for a self-aligned contact etch of silicon dioxide to an underlying thin layer of silicon nitride. The process uses difluoromethane (CH.sub.2 F.sub.2) for its strong polymer forming and a greater amount of trifluoromethane (CHF.sub.3) for its strong etching, and with a high diluent fraction of argon (Ar). The etch process is performed at a low pressure of about 20 milliTorr in a high-density plasma etching chamber.
Claims9
A process for selectively etching oxide over nitride, comprising:
- placing a substrate comprising an oxide layer overlying a nitride layer into a plasma chamber;
- injecting into said chamber a gas mixture comprising a first amount of difluoromethane, a second amount of trifluoromethane, and a third amount of an inactive gas selected from the group consisting of argon and helium, said first, second, and third amounts summing to a fourth amount;
- exciting said gas mixture into a plasma to thereby selectively etch said oxide layer over said nitride layer;
- wherein a first ratio between said first and fourth amounts has a value of 10%.+-.2%;
- and
- wherein a second ratio between said second and fourth amounts has a value of 14% .+-.2.8%.
3 more elements
Dependencies are inferred from the claim text.