Extreme ultraviolet (EUV) lithography is crucial to achieving smaller device sizes for next-generation technology, although organic resists face substantial challenges, such as low etch resistance, which limit the resolution of smaller features. Area-selective deposition (ASD) is one potential avenue to improve pattern resolution from organic EUV resists by selectively depositing material on one region of the resist, while preventing material deposition on an adjacent region. We therefore evaluate the compatibility of various organic EUV resists with area-selective atomic layer deposition (ALD) processes, including considering the effects of photo-acid generator (PAG) and EUV exposure on polymer properties and selectivity. The thermal stability of thin resist materials at the TiO2 deposition temperature (125 o C for 60 minutes) is confirmed with water contact angle and atomic force microscopy. Upon TiO2 ALD from TiCl4 and H2O, Rutherford backscattering spectrometry reveals successful TiO2 deposition on poly(tert-butyl methacrylate), poly(p-hydroxystyrene), and poly(p-hydroxystyrene-random-methacrylic acid) polymers, regardless of PAG or EUV exposure. However, TiO2 inhibition is observed on poly(cyclohexyl methacrylate). Thus, we demonstrate that EUV polymers can serve as either the growth or non-growth surface during TiO2 ASD, an insight that can be used to enable resist hardening and tone inversion applications, respectively. These results serve as a basis for further ASD studies on EUV resist materials to improve pattern resolution in next-generation devices.

Negative tone imaging (NTI) process is a method for obtaining a negative-tone reversal pattern by developing with an organic solvent. As NTI process can break-through the resolution limit of a conventional positive tone development (PTD) process at specific pattern such as trenches and contact holes, it has been applied for a mass production in 20nm and 14nm nodes devices. In NTI system, because a developer is changed from a hydrophilic aqueous solution to a hydrophobic organic solvent, it is possible to review the common resist stack which is optimized for a PTD process. In this paper, we examined the possibility of a bi-layer process using a Si-containing NTI resist. Etching selectivity between the Si-NTI resist and a SOC improved by raising Si-content of the Si-NTI resist, but resolution deteriorates as a trade-off. By suppressing swelling behavior of the Si-NTI resist with a polymer structure control, we overcame this trade-off. As a result, in sub-90 nm pitch L/S and CH patterns, the resolution of the Si-NTI resist achieved comparable level to a conventional NTI resist. In addition, SOC etching was successfully carried out by using the Si-NTI resist pattern as an etching hard mask.

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For semiconductor device manufacturing, line width roughness (LWR) and defect reduction of resists is one of the most important items to obtain high yield. In this study, we described the development of novel high absorption resists for use in extreme ultra violet (EUV) lithography system and its LWR and nano-bridge reduction capability. Herein decomposition rates of photo acid generator (PAG) and several high EUV absorption compounds were studied to clarify inefficient pass on acid generation mechanism. As a result, it is revealed that existence of decomposition pass on high EUV absorption compounds degenerates PAG decomposition efficiency. New high absorption materials were synthesized with taking into account its decomposition durability and its lithographic performance were investigated. 15-20% dose reduction keeping its LWR value and nano-bridge reduction were observed even at lower dose condition compared to non-high absorption platform.

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