High-NA EUV lithography required for continued extreme downscaling of Si devices demands ultrathin photoresists with high EUV patterning performance and etch resistance. This talk briefs our current efforts on synthesizing new organic-inorganic hybrid resists based on atomic layer deposition (ALD) techniques and characterizing their electron beam and EUV patterning characteristics. Two distinctive approaches are discussed–vapor-phase infiltration (VPI) and molecular ALD (MALD), where the former utilizes an infiltration of gaseous inorganic precursors into existing organic resists and the latter a cyclic layering of organic and inorganic moieties. Featured systems include an indium-oxide-infiltrated PMMA and a MALD hybrid resist comprising trimethylaluminum (TMA) and hydroquinone (HQ). Given the facile implementablility and control of resist composition and characteristics, the ALD-based hybrid resist synthesis has a potential for enabling high-performance EUV photoresist systems.
We investigated the hydroquinone (HQ)/trimethylaluminum (TMA) hybrid thin film synthesized by molecular atomic layer deposition (MALD) as a potential extreme ultraviolet (EUV) photoresist. The patterning characteristics of the resist was studied using electron beam lithography (EBL) and low-energy electron microscopy (LEEM), identifying energy-dependent critical exposure dose and contrast under wet development. Also identified were the reactive ion etching (RIE) characteristics, demonstrating a dry development parameter window, achieving the maximum etch contrast of ~10 nm between the regions with and without electron exposure. The results suggest the MALD approach as a viable synthesis route for developing new hybrid EUV photoresists.
Significant efforts have been dedicated to the development of inorganic-organic hybrid materials for next-generation EUV resists. Among the various synthesis, vapor-phase infiltration of metal source into existing e-beam photoresists using ALD process has drawn great attention. In this work, we have demonstrated the vapor-phase infiltration of both Hf and Al precursors into PMMA and HSQ resists, respectively. For example, under the electron exposure with 100 eV, both hybrid resists show relatively higher EUV absorption, increasing positive and negative tone. The detailed photochemical reactions of on electron exposure were investigated using an in-situ FTIR equipped with electron gun capability.
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