Selective thin film etch process

A process for selectively etching the silicon nitride layer constituent of a body comprising a layer of silicon nitride over a silicon oxide underlayer in a plasma etching chamber using a photoresist etch mask formed over the silicon nitride, with controlled high selectivity for the silicon oxide underlayer, comprising:

• positioning the masked body in the etch chamber;
• communicating into said chamber a reactive gas mixture comprising NF.sub.3, SiF.sub.4, and O.sub.2 and energizing the reactive gas mixture to form a plasma for etching the silicon nitride with a high selectivity for the photoresist and for the oxide underlayer.

A process for selectively etching a silicon nitride layer of a body which includes the silicon nitride layer over a silicon oxide underlayer with controlled selectivity for the silicon oxide underlayer, the nitride layer having a photoresist mask formed thereon, comprising:

• exposing the body to a plasma formed from a gas flow of SiF.sub.4, oxygen and NF.sub.3.

A gas mixture for selectively etching silicon nitride with high selectivity for photoresist and silicon oxide, the mixture comprising SiF.sub.4, oxygen and NF.sub.3.

The gas mixture of claim 16, further comprising a freon-containing gas for increasing the selectivity for photoresist.

A plasma process for selectively etching a film selected from silicon and silicon nitride, with high selectivity to a film of silicon dioxide, comprising:

• exposing the film to a plasma formed from a gas mixture comprising (1) SiF.sub.4 ;
• (2) fluorinated gas selected from NF.sub.3 and SF.sub.6 ;
• and (3) an oxygenated gas selected from oxygen, CO and CO.sub.2 for etching the film and simultaneously depositing silicon oxide on the oxide layer at a selected rate to offset etching of oxide layer by etchant component of plasma.

A gas mixture for etching silicon or silicon nitride with high selectivity to silicon dioxide, comprising (1) SiF.sub.4 ;

• (2) fluorinated gas selected from NF.sub.3 and SF.sub.6 ;
• and (3) oxygenated gas selected from oxygen, CO and CO.sub.2.

A process for selectively etching in a reactor chamber the silicon nitride layer constituent of a body comprising a layer of silicon nitride and a layer of silicon oxide, comprising:

• generating in the reactor a plasma formed from a gas flow of oxygen and SiF.sub.4 where the flow rate of oxygen is at least 15 percent of the SiF.sub.4 flow rate for etching the silicon nitride and simultaneously depositing silicon oxide on the silicon oxide layer to suppress etching of the silicon oxide layer.