The objective of this work is to study the process variation challenges and resolution in the Negative Tone Develop Process for 20 nm and Below Technology Node. This paper describes the effect of dose slope on CD variation in negative tone develop LELE process. This effect becomes even more challenging with standalone NTD developer process due to q-time driven CD variation. We studied impact of different stacks with combination of binary and attenuated phase shift mask and estimated dose slope contribution individually from stack and mask type. Mask 3D simulation was carried out to understand theoretical aspect. In order to meet the minimum insulator requirement for the worst case on wafer the overlay and critical dimension uniformity (CDU) budget margins have slimmed. Besides the litho process and tool control using enhanced metrology feedback, the variation control has other dependencies too. Color balancing between the two masks in LELE is helpful in countering effects such as iso-dense bias, and pattern shifting. Dummy insertion and the improved decomposition techniques  using multiple lower priority constraints can help to a great extent. Innovative color aware routing techniques  can also help with achieving more uniform density and color balanced layouts.
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Sohan S Mehta, Lakshmi K Ganta, Vikrant Chauhan, Yixu Wu, Sunil Singh, Chia Ann, Lokesh Subramany, Craig Higgins, Burcin Erenturk, Ravi Srivastava, Paramjit Singh, Hui Peng Koh, David Cho, "Process variation challenges and resolution in the negative-tone develop double patterning for 20nm and below technology node," Proc. SPIE 9425, Advances in Patterning Materials and Processes XXXII, 94250B (20 March 2015);