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N7 FinFET Self-Aligned Quadruple Patterning Modeling

How to characterize the fin pitch walk by modeling the SAQP process flow of a 7nm finFET technology.

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Authors: Sylvain Baudot, Sofiane Guissi, Alexey P. Milenin, Joseph Ervin, Tom Schram (IMEC and COVENTOR)

In this paper, we model fin pitch walk based on a process flow simulation using the Coventor SEMulator3D virtual platform. A taper angle of the fin core is introduced into the model to provide good agreement with silicon data. The impact on various Self-Aligned Quadruple Patterning process steps is assessed. Etch sensitivity to pattern density is reproduced in the model and provides insight on the effect of fin height variability.

Advanced finFET technologies use Self-Aligned Quadruple Patterning (SAQP) to define features below the resolution of 193nm immersion lithography techniques. For the 7nm finFET node, a 24nm fin pitch is targeted which requires careful adjustment of SAQP parameters to avoid a systematic pitch variation (pitch walk). Unbalanced spaces between fins lead to undesired variability for subsequent etch or deposition steps. In this paper we propose a method to characterize the fin pitch walk by modeling the SAQP process flow of a 7nm finFET technology with SEMulator3D. Our goal is to minimize the pitch walk and characterize the impact on fin height variability. In Part II, we present the process flow simulation and characterization methodology, as well as the critical parameters impacting the pitch walk. The model is applied in Part III(A) to optimize the fin pitch walk assuming an ideal core profile. The impact of a tapered profile on pitch walk is studied in Part III(B) and benchmarked against silicon data. A pattern dependent etch is introduced in Part III(C) to simulate fin height variability and characterize the consequences of pitch walk.

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