LONDON EDA software vendor Synopsys, Inc. said it is involved in a joint program with the Sematech research consortium to develop optical proximity correction (OPC) models to allow optical lithography to be used with manufacturing processes at 45-nanometer and beyond.
The program is based on mask synthesis software called Proteus and preliminary results have indicated that immersion tools using a 1.3 numerical aperture (NA) can be image-corrected for use at the 45-nm half-pitch, Synopsys (Mountain View, Calif.) said. The program’s goal is to enable the extension of immersion lithography to the 32-nm half-pitch, and extend models for optical tools with numerical apertures of 1.55 and greater.
Synopsys did not say how long the project had been running, but said the Proteus software simulates electromagnetic diffraction and scattering through the photomask.
In immersion lithography, the immersion liquid 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. Immersion also allows a lens to be designed with an NA greater than 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 that enable high yield in manufacturing.
“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,” said Shane Palmer, Sematech senior technologist and Texas Instruments assignee, in a statement issued by Synopsys.