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With the increasing drive towards smaller feature sizes in integrated circuits and the consequent use of shorter exposure wavelengths, the imaging resist layer and underlying bottom anti-reflective coating (BARC) layer are becoming thinner. At this scale, the performance of chemically amplified resists can be adversely affected by the BARC-resist interfacial interactions. These interactions can cause distortion of resist profiles and lead to footing, undercut, or pattern collapse. BARC components can immensely influence the deprotection and dissolution properties of the resist. A thorough understanding of the physico-chemical interactions at these interfaces is essential to design and develop new material platforms with minimal adverse interactions and maximum compatibility between BARC and resist. Results are reported from studies of (A) surface versus bulk chemistry of BARC materials as a function of cure temperature, (B) the dependence of the thickness and composition of the residual layer (resist material remaining on the surface of the BARC after development) on BARC components, as determined by formulating the BARC or resist with an excess of various BARC components, and (C) the dependence of the residual layer thickness on crosslink density, exposure does, and resist bake temperature. The BARC thin films and the interphase between BARC and resist were characterized with near edge x-ray absorption fine structure (NEXAFS) spectroscopy. Surface chemical properties of BARC films were derived from contact angle measurements of various liquids on these thin films. Preliminary results from these studies indicate that some BARC components may migrate to the BARC-resist interphase and act as dissolution inhibitors. Similarly, small molecule additives in the resist may migrate into the BARC layer, causing chemical modifications.
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