Modified dose correction strategy for better pattern contrast

All patterning technologies, including e-beam writing, encounter growing challenges to meet the requirements of current and future semiconductor technology nodes. For e-beam writing the electron proximity effect is one of the most prominent influencing factors and its optimal correction is a key for achieving sufficient pattern fidelity. Leading correction algorithms like PROXECCO® currently use a dose modulation strategy for correcting the electron proximity effect. For obtaining minimum feature sizes of below 50 nm and for most demanding patterns like dense line geometries additional correction strategies seem to be necessary to meet the pattern fidelity requirements of the semiconductor industry. The dense line geometries are so sensitive to suboptimal correction because of the achievable contrast in that case, which is minimal. The result is a small process window and an increased line width roughness (LWR). One of the possible modifications of the correction strategy is a combination of dose correction and a variation of the pattern shape. For the scope of this paper we will investigate the potential gains (contrast enhancement) and losses (increase in data prep and writing time) resulting from the so called "geometrically induced dose correction" method available in the current version of PROXECCO® integrated in the ePLACE® software package. ePLACE means eBeam Direct Write and Mask Data Preparation Layout Console and offers the ability to process layout data as well as a state-of-the-art visualization and exposure simulation capabilities. In this paper we show that especially the simulation capability can be used to reduce experimental work significantly. The "geometrically induced dose correction" method is in fact a shape size biasing operation followed by a special dose correction to meet the intended shape edges. By theoretical considerations and by applying the ePLACE® automatic simulation & measurement feature to a huge number of measurement areas we investigate the influence of the geometrically induced dose correction on exposure contrast and CD uniformity for test and real patterns. We also discuss how the geometrically induced dose correction influences the data prep time and finally the e-beam writing time.