Selective etch of silicon nitride

A method of etching a patterned substrate having exposed silicon nitride and exposed silicon in a substrate processing region of a substrate processing chamber, the method comprising:

• flowing a nitrogen-and-oxygen-containing precursor into a first remote plasma region while forming a first remote plasma in the first remote plasma system to produce oxidizing plasma effluents;
• flowing a fluorine-containing precursor into a second remote plasma region, distinct from the first remote plasma region, while forming a second remote plasma in the second remote plasma region to produce radical-fluorine;
• combining the oxidizing plasma effluents with the radical-fluorine in the substrate processing chamber, wherein the oxidizing plasma effluents and the radical-fluorine are flowed through separate channels of a multi-channel showerhead;
• and
• selectively etching the exposed silicon nitride at a greater etch rate than the exposed silicon.

A method of etching a patterned substrate having exposed silicon nitride and exposed silicon in a substrate processing region of a substrate processing chamber, the method comprising:

• flowing N2O into a first remote plasma disposed outside the substrate processing chamber to produce oxidizing plasma effluents;
• flowing NF3 into a second remote plasma, separate from the first remote plasma, to produce fluorine-containing plasma effluents, wherein the NF3 is substantially not excited in the first remote plasma;
• combining the oxidizing plasma effluents with the fluorine-containing plasma effluents in the substrate processing chamber;
• selectively etching the exposed silicon nitride relative to the exposed silicon.