Photoresist for Extreme Ultraviolet Lithography

Lithography enabled nanoscale fabrication in the semiconductor industry, is also the primarily driven force for the microelectronics revolution. In the history of photolithography, scientists have been working on reducing the light wavelength for higher lithographic resolution. With the rapid development of semiconductors, today's 193-nm immersion lithography is approaching its physical limits. Extreme ultra-violet (EUV) lithography with a wavelength of 13.5 nm has been emerged as the most promising candidate to continue Moore's law. However, the dramatic decrease of the wavelength of the light source has brought many technological challenges on both the machine side and the photoresist side for semiconductor high volume manufacturing (HVM). Historically, the invention of chemically amplified resists (CARs) with significantly improved sensitivity had helped overcome the power output challenge of the light source in deep ultra-violet (DUV) lithography. A possible solution for current EUVL challenges is continually developing new photoresists to efficiently absorb the EUV light, even though polymer-based CARs have been widely used for decades. This review discusses the challenges in EUVL and the progress in the EUV photoresists materials, including polymer, molecular glass, and metal-oxide nanoparticles type photoresists. A brief discussion of the development strategies and future challenges for EUV photoresists is also included.