Future generation photomasks for advanced lithography
The PhD research topic “Future generation photomasks for advanced lithography” involves fundamental understanding and new solutions for photomasks enabling next generation lithography through simulation modeling, experimental characterization and imaging verification. Optical lithography is the fundamental process in microchip fabrication that transfers the patterns from the photomask onto a silicon wafer using a reduction optical system. As industry is obsessed with smaller dimensions, usage of smaller wavelength of light such as 13.5 nm in EUV range is indispensable. Thus, the feature sizes on photomask are now approaching the dimensions of the optical wavelength, which generates new optical effects. These effects must be understood, in order to accurately predict and control the imaging. The goal is to examine innovative solutions and technologies for photomasks to enable next generation lithography. We will investigate the optical properties, stability and reactivity of new mask materials through complementary characterization techniques such as EUV Reflectometry (EUVR), Transmission Electron Microscopy (TEM), X-Ray Diffractometry (XRD), X-Ray Photoelectron Spectroscopy (XPS). We will combine this with rigorous simulations based on electromagnetic wave theory of light and lithography process model to obtain thorough understanding of the optical effects seen at the photomask and how they transfer to wafer level. Based on modeling predictions and mask requirements, a prospective material can be identified, and an actual photomask with selected geometries will be fabricated in order to investigate and validate it’s imaging performance.