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24 May 2004 Metrology exposure-induced resist and ARC damage
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Timbre's Optical Digital Profilometry (ODP) system is a scatterometry-based metrology. In lithography applications, the critical dimension (CD) is often patterned photoresist (PR) on an anti-reflective coating (ARC). When a patterned PR is exposed to the broadband light of the optical metrology tool, a change in reflectance may occur. For "sensitive" film stacks, the changing optical signals then produce changing ODP CD, sidewall angle, and film thickness measurements. This report summarizes the results of several resist and ARC stacks subjected to the repeated broadband light exposure of a Therma-Wave CCD-i reflectometry system. The purpose is to determine which resist-ARC stacks are significantly affected by repeated measurement exposure, and to quantify these effects. Our analysis shows that very little metrology exposure-induced change occurs for ArF resists. For KrF resists, the change is closely related to the type of KrF resist used; acetal-types incur large spectral changes upon repeated exposure, whereas ESCAP (Environmentally Stable Chemically Amplified Photoreist) resists measurements are very stable. Significant reduction of metrology induced spectral and CD change as achieved by incorporating a long-pass filter into the system. The changes due to a single measurement are negligible, however, they can be substantial for a sensitive material when characterizing metrology repeatability. Thus, it is recommended to use stable materials, such as oxide gratings, for metrology characterization.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jackie Yu, Anita Viswanathan, Mokoto Miyagi, Junichi Uchida, Lawrence Lane, Kelly A. Barry, Machi Kajitani, Toshihiko Kikuchi, K. C. Chan, and Fred E. Stanke "Metrology exposure-induced resist and ARC damage", Proc. SPIE 5375, Metrology, Inspection, and Process Control for Microlithography XVIII, (24 May 2004);

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