Patent ID: 8728947

Claim:
A method for opening a conformal layer at the bottom of a high aspect ratio contact via on a substrate, comprising: providing a substrate having a first layer with a via pattern formed therein and a second layer conformally deposited on said first layer and within said via pattern, said second layer extending along a top surface of said first layer, wrapping over a corner at an entrance to said via pattern, and penetrating into said via pattern while conforming to the sidewalls and the bottom of said via pattern to establish a contact via pattern, and measuring initial critical dimensions (CD) at approximately mid-depth of said contact via pattern and at said corner at said entrance; etching through said second layer at the bottom of said contact via pattern to extend said contact via pattern through said second layer and form a contact via while retaining at least part of said second layer on said top surface of said first layer, said corner at said entrance to said via pattern, and said sidewalls of said via pattern, wherein said etching is performed by irradiating said substrate with a gas cluster ion beam (GCIB) according to a GCIB etching process; and measuring final critical dimensions (CD) at approximately said mid-depth of said contact via pattern and at said corner at said entrance; wherein said etching includes selecting a beam energy distribution for said GCIB to reduce erosion of a corner profile for said second layer to a value of 10 nm or less, wherein said erosion of said corner profile is assessed by measuring a difference between said initial and final CDs at said corner at said entrance.