20 March 2018 Co-optimization of exposure dose and etch process for SAQP pitch walk control
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Abstract
Spacer-assisted pitch multiplication is a patterning technique that is used on many different critical layers for memory and logic devices. Pitch walk can occur when the spacer process, a combination of lithography, deposition and etch processes, produce a repeating, non-uniform grating of space / line CDs. It has been shown that for spacer-assisted double patterning (SADP), where the lithography pitch is doubled, pitch walk can be reduced by controlling the exposure dose such that the uniformity of the final SADP spaces defined by the core resist mandrel (S1) is balanced with the final SADP space defined by the distance between adjacent SADP lines (S2). For higher pitch multiplications, starting with spacer-assisted quadruple patterning (SAQP) reducing systematic pitch walk with exposure dose becomes more complex.

Co-optimization of the lithography and etch processing is expected to be required to achieve the best pitch walk control. Previous work has shown that improving the across wafer CD uniformity of the line patterns after core etch has limited impact on the space CD uniformity after the SADP process, whereas the CD uniformity of the spaces after SAQP did show some dependence. There are additional space populations created by an SAQP process. The variation of these different populations, along with the spacer deposited line populations, is the root cause of the non-uniform grating that results in pitch walk. The complex interactions of the lithography and etch processes’ impact on the CD and profile need to be understood to produce the optimal performance.

Pitch walk is a component of the overall Edge Placement Error (EPE) budget. With current nodes using SAQP for multiple device layers and future nodes expected to continue to implement this patterning technique, minimization of pitch walk variability is an important part of overall patterning optimizations. In this work, we will show how cooptimized exposure dose and etch processes for SAQP patterning can improve pitch walk performance. We will provide a target exposure dose metric for a 32nm pitch SAQP grating. The methodology for achieving the best pitch walk performance by combination of etch process optimization with dose correction will also be shown.
Conference Presentation
© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Mark John Maslow, Mark John Maslow, Vadim Timoshkov, Vadim Timoshkov, Ton Kiers, Ton Kiers, Tae Kwon Jee, Tae Kwon Jee, Liesbeth Reijnen, Liesbeth Reijnen, Kaushik Kumar, Kaushik Kumar, Marc Demand, Marc Demand, Carlos Fonseca, Carlos Fonseca, Florin Cerbu, Florin Cerbu, Guillaume Schelcher, Guillaume Schelcher, Christophe Beral, Christophe Beral, } "Co-optimization of exposure dose and etch process for SAQP pitch walk control", Proc. SPIE 10587, Optical Microlithography XXXI, 1058704 (20 March 2018); doi: 10.1117/12.2297345; https://doi.org/10.1117/12.2297345
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