October 5, 2005 – Synopsys Inc. and SEMATECH will jointly develop advanced optical proximity correction (OPC) models for the extension of optical lithography. A key goal of the program, part of SEMATECH’s 193nm Immersion Lithography Extendibility Project, is to facilitate better understanding of the challenges in process nodes beyond 45nm so participants can develop appropriate software and manufacturing processes. Synopsys will provide its Proteus mask synthesis stoftware.
The program’s preliminary modeling results have been strong, indicating that immersion tools using a 1.3 numerical aperture (NA) can be image-corrected for use at the 45nm half-pitch. The objective is to eventually enable the extension of immersion lithography to the 32nm half-pitch, and extend models for optical tools with a 1.55 or greater NA.
“Since advanced immersion tools are just now being developed, modeling is critical to determining how far we can go with immersion lithography. The Synopsys tools have proven useful in developing the OPC models that will allow us to push the immersion frontier,” said Shane Palmer, SEMATECH senior technologist and Texas Instruments assignee. “SEMATECH’s project is geared toward preparing tools for the next generation of immersion scanner that will use higher index fluids, NA above 1.3 and full polarization control. The results will help SEMATECH member companies make informed decisions about appropriate imaging tools for advanced technology cycles.”
In immersion lithography systems, the immersion liquid (such as pure water) is placed between an exposure tool’s projection lens and a wafer, and the liquid’s refractive properties are used to create higher resolution images than a “dry” lens system will allow. Immersion also allows a lens to be designed with an NA >1 which permits even further resolution improvement. Accurate modeling of the optical distortions introduced by these “hyper-NA” projection systems is required in order to validate designs, perform OPC, and add reticle enhancement technologies (RET) that enable high yield in manufacturing.
Synopsys’ Proteus software facilitates high-speed accurate modeling by enabling engineers to simulate electromagnetic diffraction and scattering through the photomask. The software also provides the flexibility for engineers to progress through the various modeling steps required for immersion lithography. The resulting silicon image helps process development engineers better understand the predictability and yield of their processes.