Patent ID: 7271108

Claim:
A method for forming etch features in an etch layer over a substrate, comprising: forming an etch mask stack formed by at least one layer over the etch layer; forming a first mask over the etch mask stack wherein the first mask defines a plurality of spaces with widths and a first pitch; forming a sidewall layer over the first mask wherein the sidewall layer reduces the widths of the spaces defined by the first mask, wherein the forming a sidewall layer over the first mask comprises at least two cycles, wherein each cycle comprises: a deposition phase with a first gas chemistry to form a deposition plasma to form a deposition over the sidewalls of the first mask; and a profile shaping phase with a second gas chemistry to shape the profile of the deposition over the sidewalls of the first mask, wherein the first gas chemistry is different than the second gas chemistry; etching a first set of features at least partially into the etch mask stack through the sidewall layer, wherein the features of the first set of features have widths that are smaller than the widths of the spaces defined by the first mask; removing the mask and sidewall layer; performing an additional feature step, comprising: forming an additional mask over the etch mask stack, wherein the additional mask defines a plurality of spaces with widths; forming a sidewall layer over the additional mask, wherein the sidewall layer reduces the widths of the spaces defined by the additional mask; etching a second set of features at least partially into the etch mask stack through the sidewall layer, wherein the features have widths that are smaller than the widths of the spaces defined by the additional mask, wherein the features further have a second pitch smaller than the first pitch; and removing the mask and sidewall layer; and etching a plurality of features into the etch layer through the first set of features and the second set of features in the etch mask stack.