Retargeting of forbidden-dense-alternate structures for lithography capability improvement in advanced nodes

In advanced semiconductor technology nodes, the forbidden pitch effect induced by the destructive interference between neighboring features always leads to poor printing quality. This effect becomes more prominent when the forbidden pitch structure combines with dense pitch structures, which is called the forbidden-dense-alternate (FDA) structure. To overcome its influence on lithographic performance, the design rules can be revised at the cost of design tolerance. Another method is to optimize the source map with the risk of bringing the performance attenuation onto other patterns. This work demonstrates a retargeting method on the weak point in FDA structures. This method can improve the lithographic performance of FDA structures and allow more tolerance to the source mask optimization and design rules. As a result, more process tuning margin can be reserved for other modules, such as optical proximity correction and process integration, in order to improve the yield.