HIGH-FIDELITY LITHOGRAPHY

Of primary importance in lithography is understanding internal molecular forces, characterized by chemical contrast, which, when uncontrolled, can lead to pattern uncertainty and line edge roughness/line width roughness (LER/LWR). Another key to achieving high-fidelity lithography is to control resist and substrate interaction ( or nanoscale affinity), which can be characterized by chemical contrast at the base of the resist. Both of these factors are important in determining ultimate resolution capability. Because these forces are difficult to model, the effectiveness of matching performance to simulation becomes more complicated. As a result, the cost of optical proximity correction ( OPC) is increasing to match the requirements for pattern accuracy. This paper will review how these factors relate to advanced lithography concepts, and experimental results of trilayer immersion lithography of high foot contrast will be presented to show striking improvement over conventional minimum substrate reflection stack.