Litho1-Litho2 Proximity Differences For Lele And Lple Double Patterning Processes

Double Patterning (DP) is the most immediate candidate for IC technologies requiring pitches below the single exposure capabilities of today's ArF immersion scanners. Litho-Process-Litho-Etch (LPLE) DP processes potentially offer substantial cost and throughput benefits over the more proven Litho-Etch-Litho-Etch (LELE) approaches. However, LPLE DP approaches typically use a different resist for each lithography step and there are many potential process and material interactions between the lithographic layers which could have an impact on proximity effects after full DP flow.In this work the impact of process and material interactions on proximity effects is investigated for a metal 1 double trench LELE process and a poly double line LPLE process. The process windows for several pitches and proximity behaviour of both pattern 1 and pattern 2 is studied. Results obtained from a single patterned wafer are compared with results from a single patterned and double patterned area on a double patterned wafer.The results reveal that for the LPLE case there are process window and proximity differences between single and double patterned wafers showing the influence of a neighbouring line from another patterning step. The process window differences do not just consist of a simple shift along the dose axis, which implies that the Litho 2 OPC models would need to be aware of the underlying pattern 1 topography.For a few specific cases the experimental results are compared to calibrated Litho-Process-Litho (LPL) Prolith model predictions. The Prolith simulation model matches the experimental data and helps to distinguish between chemical, optical and processing effects as the root cause of the observed differences.