31 March 2014 Study on abnormal intra-field CD uniformity induced by Efese-tilt application upon complex leveling scheme
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Abstract
Critical dimension uniformity (CDU) of hole layer is becoming more and more crucial and tightened alongside with the technology node being driven into 28 nm and beyond, since the critical dimension (CD) variation of 2-dimensional (2D) hole pattern is intrinsically harder to control than that of 1D pattern (line/space). As the process window becomes more marginal with the more advanced technology node, although at the cost of contrast loss, EFESE tilt (focus drilling method) is one handy trick for its DOF enhancement capability (1-3). We observed an abnormal up to 6 nm ADI CD trend-down in Y-direction (exposure scan direction) in the strictly repeated via-hole patterns within an about 8 mm x 6 mm chip in condition 1 wafer with pre-layer patterns (short as C1 wafer) where EFESE tilt is applied. No CD trend-down or trend up in X-direction. This C1 hole layer uses EFESE tilt to improve DOF. This CD trend-down phenomenon is thoroughly investigated and a model of “effective EFESE tilt” is proposed and verified. Based on the model, we made a further step into the assessment of another focus drilling method, i.e. EFESE High Range (HR) and evaluate its performance under the same complex leveling scheme. Through all this analysis, we give an insight of the safety zone for applying EFESE tilt for future reference.
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Guogui Deng, Jingan Hao, Boxiu Cai, Bin Xing, Xin Yao, Qiang Zhang, Tianhui Li, Yi-Shih Lin, Qiang Wu, Xuelong Shi, "Study on abnormal intra-field CD uniformity induced by Efese-tilt application upon complex leveling scheme", Proc. SPIE 9052, Optical Microlithography XXVII, 905229 (31 March 2014); doi: 10.1117/12.2046308; https://doi.org/10.1117/12.2046308
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