Proceedings Article | 5 April 2011
KEYWORDS: Optical proximity correction, Extreme ultraviolet, Photomasks, Reticles, Extreme ultraviolet lithography, 193nm lithography, Lithography, Manufacturing, Optical lithography, Model-based design
Although technical issues remain to be resolved, EUV lithography is now a serious contender for critical
layer patterning of upcoming 2X node memory and 14nm Logic technologies in manufacturing. If
improvements continue in defectivity, throughput and resolution, then EUV lithography appears that it will
be the most extendable and the cost-effective manufacturing lithography solution for sub-78nm pitch
complex patterns. EUV lithography will be able to provide a significant relaxation in lithographic K1
factor (and a corresponding simplification of process complexity) vs. existing 193nm lithography. The
increased K1 factor will result in some complexity reduction for mask synthesis flow elements (including
illumination source shape optimization, design pre-processing, RET, OPC and OPC verification).
However, EUV does add well known additional complexities and issues to mask synthesis flows such as
across-lens shadowing variation, across reticle flare variation, new proximity effects to be modeled,
significant increase in pre-OPC and fracture file size, etc.
In this paper, we investigate the expected EUV-specific issues and new requirements for a production
tapeout mask synthesis flow. The production EUV issues and new requirements are in the categories of
additional physical effects to be corrected for; additional automation or flow steps needed; and increase in
file size at different parts in the flow. For example, OASIS file sizes after OPC of 250GigaBytes (GB) and
files sizes after mask data prep of greater than three TeraBytes (TB) are expected to be common. These
huge file sizes will place significant stress on post-processing methods, OPC verification, mask data
fracture, file read-in/read-out, data transfer between sites (e.g., to the maskshop), etc. With current methods
and procedures, it is clear that the hours/days needed to complete EUV mask synthesis mask data flows
would significantly increase if steps are not taken to make efficiency improvements. Therefore, we also
analyze different options for reducing or alleviating the EUV specific issues mentioned above and the
expected cost/benefit tradeoffs associated with these options. The options include understanding the
accuracy vs. run-time benefit of different rule-based and model-based approaches for several correction
issues; predicting the implications and improvements expected with different flow automation options; and
estimating possible productivity improvements with different flow parallelization choices and upcoming
multi-core processors. Optimal combinations of options and accuracy/effort/runtime results can be seen to
enable EUV lithography tapeout flows to achieve equal or better total time when compared to current
193nm optical lithography tapeout flow times.
