Patent ID: 8277670

Claim:
A method for etching features in a dielectric layer through a photoresist (PR) mask, the PR mask being patterned using laser light having a wavelength not more than 193 nm, said method comprising: pre-treating the PR mask with a noble gas plasma so as to harden the PR mask material by compression without causing chemical reactions; and providing a plurality of cycles, wherein each cycle comprises: a deposition phase that deposits a deposition layer over the PR mask, the deposition layer covering a top and sidewalls of mask features of the PR mask; and a shaping phase that shapes the deposition layer deposited over the PR mask, wherein an antireflection layer (ARL) is formed over the dielectric layer below the patterned PR mask, and wherein in each cycle, the shaping phase first etches the ARL in a bottom of the mask features and trims the PR mask, and the deposition phase deposits the deposition layer on the PR mask and further etches the ARL in the bottom of the mask features.