Organometallic photoresists for advanced Extreme Ultraviolet Lithography (EUVL)
This PhD project aims to develop an alternative photoresist based on organometallics chemistry for Extreme Ultraviolet (EUV) lithography. Moore’s Law predicted that number of transistors per IC will be doubled every year. And to accommodate this increase the key is the dimension (size and density) of the pattern transferred to the wafer by lithography. e. The extreme ultra-violet (EUV) lithography, at a wavelength of 13.5 nm is the leading-edge technology to pattern small features and recently it has been introduced for high-volume manufacturing (HVM) in the semiconductor industry for the 7 nm technology node (N7). However, the capability of EUV to work upto the mark strongly depends upon the photoresist used in the process. Typically, organic chemically amplified resists (CAR) are used in for EUV lithography. They used the mechanism of photo acid generation which then diffuses to switch the solubility of the resist. However, this diffusion can also result in the line edge roughness and causes stochastic defects in the patterns. In the recent years, novel spin-on materials such as metal oxide resist, nanoparticles, molecular resist (called non-CARs), have been introduced and investigated to overcome current patterning limits. They rely on a pattern solubility switch mechanism other than the acid diffusion and it is supposed to provide better control in pattern roughness and higher sensitivity since based on high absorbing EUV elements and lower chemical stochastics since single-component based. Yet, the detailed mechanisms are not studied yet. Crucial to elucidate the mechanism is to generate a deeper insight into the light-matter interaction in the photoresist during EUVL. The high-energy EUV photons (92 eV) generate secondary electrons through interaction with the resist material trigger the desired reactions in the resist that needs to be developed afterwards. The efficiency with which the primary beam interacts with the resist film to produce secondary electrons depends on the capacity of the resist to absorb EUV radiation. The aim of this PhD project is to understand and develop novel organometallic EUV photoresists. Starting from existing materials (e.g., metal-organic frameworks), novel materials sensitive to low-energy electrons will be developed for their characterization, functionalization and stability studies ultimately aiming to identify potential EUV photoresists that can address current EUV resist issues and can ultimately satisfy the needed requirement for future technology nodes.