Optical elements patterning

A method for processing a substrate with a gas cluster ion beam (GCIB), the method comprising:

• patterning a first mask layer disposed over the substrate;
• forming a second mask layer over the patterned first mask layer of the substrate;
• and
• etching a portion of the second mask layer such that a remaining surface of the portion of the second mask layer is slanted with a slope relative to a major surface of the substrate, the etching comprising:
• receiving, at a GCIB controller, first control signals from a tool controller to change a GCIB process parameter during the etching, the change in the GCIB process parameter providing first location-specific variations in etching by a first GCIB;
• scanning the first GCIB across a portion of the substrate according to the first control signals to form the slope of the remaining surface of the portion of the second mask layer;
• receiving, at the GCIB controller, second control signals from the tool controller to adjust the GCIB process parameter during the etching, the adjusting providing second location-specific variations in etching by a second GCIB, the second location-specific variations being different from the first location-specific variations;
• and
• scanning the second GCIB across the portion of the substrate according to the second control signals.

A method of fabricating a plurality of optical elements from a substrate, the method comprising:

• selecting a first portion of the substrate for a first optical element to be formed that has an elongated shape along a first direction;
• selecting a second portion of the substrate for a second optical element to be formed that has the elongated shape along a second direction different from the first direction;
• and
• etching the substrate with a particle beam to form a first recess pattern with varying depth on the first portion of the substrate and a second recess pattern with varying depth on the second portion of the substrate, wherein etching the substrate with the particle beam comprises scanning the particle beam over the substrate while changing a particle beam process parameter to provide location-specific variations in etching by the particle beam.