Present challenges and solutions in sampling and correction for 45nm
Conventional OPC, also known as site-based OPC, has relied on rules-based fragmentation and site placement since its inception. The issues that arose in earlier generations around imprecise site and fragmentation placement, relative to the exact location of proximity effects, has been illustrated in earlier works but generally did not produce catastrophic results. However, when coupled with the large process biases, strong RET, and accuracy requirements for 45 nm and future nodes, this imprecision can produce catastrophic results. This work will report on efforts to use model-directed site and fragmentation placement, as well as inclusion of process window knowledge into the site-based OPC flow to address varied sources of errors and relative results with different approaches. In addition to the conventional site-based OPC, a new breed of tool that avoids sites in favor of fully gridded, or dense, simulation is rapidly maturing. The new approach allows more intelligence to be built into the OPC engine such that fragmentation and error sampling are more automated and thus less error prone. Using the same layout data, we will also present a snapshot of the new tool’s results.
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