Patent ID: 8722542

Claim:
A method for patterning a layer at a bottom of a high aspect ratio feature of a substrate, comprising: providing the substrate having a first layer with a feature pattern therein overlying a second layer, wherein the feature pattern is characterized with an initial critical dimension (CD), an initial corner profile, and an aspect ratio of 5:1 or greater; and etching through at least a portion of the second layer at the bottom of the feature pattern to extend the feature pattern at least partially into the second layer while retaining a final CD within a threshold of the initial CD and a final corner profile within a threshold of the initial corner profile using a gas cluster ion beam (GCIB) etching process, wherein the GCIB etching process comprises: holding the substrate securely within a reduced-pressure environment; forming the GCIB from a pressurized gas that includes an etching gas that includes a carbon (C) element, a hydrogen (H) element, and a halogen element, wherein the etching gas includes a mono-substituted halomethane, a di-substituted halomethane, a tri-substituted halomethane, and any combination of two or more thereof; accelerating the GCIB to the reduced-pressure environment; and irradiating the accelerated GCIB onto at least a portion of the substrate to selectively etch the portion of the second layer.