Alternative Developer Solutions and Processes for EUV and ArFi Lithography

The application of alternative developers for both extreme ultraviolet (EUV) and 193-nm immersion (“ArFi”) lithography is investigated by focusing on their effects on the “Defect-Not-Found” (DNF) margins. In case of EUV lithography, defects primarily comprise line bridging at the underdose region and line breaks at the overdose region. The application of a 0.26-N tetrabutylammonium hydroxide (TBAH) developer solution when compared to that of a 0.26-N tetramethylammonium hydroxide (TMAH) developer solution resulted in improved resist sensitivity while maintaining the same DNF margin. In case of ArFi lithography, defects primarily comprise line bridging at the underdose region and pattern collapse at the overdose region. The same improvement that has been mentioned above can be observed with respect to the resist sensitivity using the TBAH developer solution. However, the TBAH developer solution significantly minimizes the pattern collapse at the overdose region, further extending the minimum line pattern size. This translated to significant improvements in both the exposure latitude (EL) and overdose margin (OM) and resulted in a significant increase in the DNF margin. Furthermore, the application of a non-ionic surfactant type additive on the TMAH developer solution demonstrates resist sensitivity improvement and pattern collapse mitigation. Increased EL and OM values were observed, which also resulted in increased DNF margin. Results indicate the advantages of utilizing alternative developer solutions in improving the DNF margins.