Etching carbon layer using doped carbon as a hard mask
Methods for etching features into carbon material using a metal-doped carbon-containing hard mask to reduce and eliminate redeposition of silicon-containing residues are provided herein. Methods involve depositing a metal-doped carbon-containing hard mask over the carbon material prior to etching the carbon material, patterning the metal-doped carbon-containing hard mask, and using the patterned metal-doped carbon-containing hard mask to etch the carbon material such that the use of a silicon-containing mask during etch of the carbon material is eliminated.
1. A method comprising:
providing a substrate comprising a substantially dopant-free amorphous carbon layer to be etched;
forming a patterned silicon-free doped carbon-containing layer over the substantially dopant-free amorphous carbon layer; and
prior to etching the substantially dopant-free amorphous carbon layer, completely removing a silicon-containing patterned mask;
etching the substantially dopant-free amorphous carbon layer in a silicon-free environment using the patterned silicon-free doped carbon-containing layer to form a patterned substantially dopant-free amorphous carbon layer by introducing an oxygen-containing chemistry to etch the substantially dopant-free amorphous carbon layer,
wherein the substantially dopant-free amorphous carbon layer has a modulus between about 60 GPa and about 160 GPa, and
wherein etching the substantially dopant-free amorphous carbon layer comprises forming features in the patterned substantially dopant-free amorphous carbon layer having an ellipticity of between about 0.67 and about 1.03.
2. The method of claim 1 , wherein the patterned silicon-free doped carbon-containing layer is silicon-free.
3. The method of claim 1 , wherein forming the patterned silicon-free doped carbon-containing layer comprises forming a patterned mask on a doped carbon-containing layer and etching the doped carbon-containing layer using the patterned mask to form the patterned silicon-free doped carbon-containing layer.
4. The method of claim 3 , further comprising prior to etching the substantially dopant-free amorphous carbon layer, removing the patterned mask.
5. The method of claim 3 , wherein the patterned mask comprises silicon.
6. The method of claim 5 , wherein the patterned mask comprises silicon oxycarbide or silicon oxynitride.
7. The method of claim 3 , wherein ratio of thickness of the patterned mask to thickness of the doped carbon-containing layer is between about 1:5 and about 1:7.
8. The method of claim 3 , wherein the etching of the substantially dopant-free amorphous carbon layer consumes substantially all of the patterned mask.
9. The method of claim 3 , wherein the patterned mask is formed by depositing a mask material over the doped carbon-containing layer, developing a patterned resist over the mask material, and etching the mask material relative to the doped carbon-containing layer using the patterned resist.
10. The method of claim 1 , wherein the patterned silicon-free doped carbon-containing layer comprises a dopant selected from the group consisting of boron, titanium, tungsten, tantalum, tin, aluminum, and combinations thereof.
11. The method of claim 1 , wherein forming the patterned silicon-free doped carbon-containing layer comprises forming features having feature openings with a width between about 16 nm and about 120 nm.
12. The method of claim 1 , wherein etch rate of the substantially dopant-free amorphous carbon layer during the etching of the substantially dopant-free amorphous carbon layer is at least about three times faster than etch rate on the patterned silicon-free doped carbon-containing layer.
13. The method of claim 1 , wherein ratio of thickness of the patterned silicon-free doped carbon-containing layer to thickness of the substantially dopant-free amorphous carbon layer is between about 1:5 and about 1:8.
14. The method of claim 1 , wherein the etching of the patterned silicon-free doped carbon-containing layer is performed using a bias.
15. The method of claim 1 , wherein the etching is performed using one or more gases that form volatile byproducts with the patterned silicon-free doped carbon-containing layer and the substantially dopant-free amorphous carbon layer without redepositing material onto substrate surfaces.
16. The method of claim 1 , wherein the patterned silicon-free doped carbon-containing layer is doped with boron and the etching of the substantially dopant-free amorphous carbon layer is performed in a silicon-free environment.
17. The method of claim 1 , wherein the substantially dopant-free amorphous carbon layer has a thickness between about 50 nm and about 120 nm.
18. The method of claim 1 , wherein the substantially dopant-free amorphous carbon layer comprises between about 15% and about 50% sp3 bonds.