As IC dimensions continue to shrink beyond the 22nm node, optical single exposure cannot sustain the resolution
required and various double patterning techniques have become the main stream prior to the availability of EUV
lithography. Among various kinds of double patterning techniques, positive splitting pitch lithography-etch-lithographyetch
(LELE) double patterning is chosen for printing complex foundry circuit designs. Tighter circuit CD and process
margin control in such positive splitting pitch LELE double patterning process becomes increasingly critical especially
for topography issues induced by the 1st mask patterning with the 2nd mask exposure. In this paper, laser parameters,
topography issues with the 2nd mask exposure, and SMO effects on CD performances are described in terms of the
proximity CD portion of the scanner CD budget. Laser parameters, e.g. spectral shape and bandwidth, were input into the
photolithography simulator, Prolith, to calculate their impacts on circuit CD variation. Mask-bias dependent lithographic
performance was calculated and used to illustrate the importance of well-controlled laser performance parameters.
Recommended laser bandwidth, mask bias and topography requirements are proposed, based on simulation results to
ensure that the tight CD control (< 1nm) required for advanced technology node products can be achieved.