Innovative Techniques for High NA EUV: Achieving Robustness in Patterning

The semiconductor industry is actively moving towards the mass production adoption of EUV (Extreme Ultraviolet) lithography technology to achieve continuous device miniaturization and increased integration. Furthermore, the development of ultrafine patterning technology based on High Numerical Aperture (High NA, 0.55 NA or higher) EUV exposure equipment is emerging as a key challenge for next-generation nodes. High NA EUV offers the strong theoretical advantage of improving resolution by approximately 1.5 times. However, it also presents several technical challenges, including a severe reduction in Depth of Focus (DOF), increased optical distortion, pattern distortion, higher defect rates, and a compressed process window. 

This presentation focuses on the primary technical challenges for ensuring mass production readiness of High NA EUV processes, particularly addressing the decline in process stability due to DOF reduction. A common strategy to secure DOF is reducing PR thickness, which helps improve the process window but also leads to the significant side effect of insufficient PR remaining thickness. This insufficiency can hinder the pattern transfer to the underlying hardmask or substrate, representing a critical risk factor for process failure. 

To overcome these issues, we discuss the potential of applying technologies that induce changes in the properties of photoresist (PR) to ensure sufficient etch resistance and pattern transfer capability, even with reduced PR thickness.