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.