Cell-based Optical Proximity Correction Technology

The progress of IC integration has kept the Moore's Law for the recent several decades. This has brought tremendous change and many new requirements in IC design and manufacturing. One of such changes is the prevailing use of RETs (Resolution Enhancement Techniques). As the feature size decreases below the wavelength of the illumination system, the diffraction and other effects arising from resist developing and etching causes more and more distortion in the pattern transfer process. Today, new chips with very small feature size can not be manufactured without the support of RETs, OPC (Optical Proximity Correction) is one of the most important technologies in such RETs. Although OPC has greatly extended the ability of photolithography, after getting into the 90nm technology node, more and more new problems become more obvious, like the computation complexity, the low flexibility and the difficulty in utilizing the hierarchical structure in GDSII. These issues have restricted the IC manufacturing ability.We proposed in this paper a new Cell-based OPC method, including the preparation of the pre-OPCed cell library, the offset initialization and the fast dynamic adjustment algorithm. This new method solved the issue of interactions between neighboring patterns and proposed the Segment-Moving Map solution to observe and analyze the range and shape of the interacting region, hence fully explored the hierarchical structure in the OPC process to reduce the computational cost and time-to-market. On the other hand, this method provides the pre-corrected cell library for the design stage, which can help to increase the flexibility of design and modification.The EPE (Edge Placement Error) is used in our experiments to analyze the error of our Cell-based OPC method. The result shows that this method achieved 5X speedup while maintaining the same accuracy compared with the conventional OPC.