BackgroundExtreme 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.AimEvaluate the potential for area-selective deposition (ASD) to improve EUV pattern resolution (e.g., by increasing etch resistance).ApproachWe evaluate thermal compatibility, atomic layer deposition growth rate, and selectivity for TiO2 ASD on various organic EUV resist materials using water contact angle, Rutherford backscattering spectrometry, and X-ray photoelectron spectroscopy. The effects of photo-acid generator (PAG) and EUV exposure on polymer properties and selectivity are considered.ResultsThe organic resist materials studied demonstrate thermal compatibility with TiO2 ALD (125°C for 60 min). The TiO2 ALD process from TiCl4 and H2O proceeds readily on poly(tert-butyl methacrylate), poly(p-hydroxystyrene), and poly(p-hydroxystyrene-random-methacrylic acid) polymers, with and without PAG incorporation, in either the as-formed or EUV exposed state. However, TiO2 is inhibited on poly(cyclohexyl methacrylate).ConclusionsWe demonstrate that as-formed EUV resists can serve as either the growth or nongrowth surface during TiO2 ASD, thereby enabling 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.
In the last years, the continuous efforts on the development of extreme ultraviolet lithography (EUVL) have allowed to push the lithographic performance of the EUV photoresists on the ASML NXE:3400 full field exposure tool, however, stochastic resist roughness, local critical dimension uniformity (LCDU) and pattern defectivity at nano-scale are still the major limiting factors of the lithographic process window of EUV resist when looking at sub-40nm pitches for both linespace (LS) and contact hole (CH) applications, especially in the low exposure dose regime [1]. To be effective during the lithographic EUV resist screening evaluation phase for such tight pitches, imec has implemented since 2018 [2] additional metrology analysis after resist development inspection (ADI) to further quick feedback on the quantification of nano-failures (nano-bridges, broken lines, merging or missing contacts) induced by a stochastic EUV patterning regime, and thus to improve the resist design at lithographic step in a faster manner. In this work, we have further extended the examination of the resist performance introducing additional metrology analysis after pattern transfer in a silicon nitride (SiN) substrate. We present the characterization results on 40nm and 36nm pitch staggered dense contact holes looking at both lithographic and etching knobs to mitigate the patterning process stochastic issues, confirming that the holistic litho-etch approach is an important and necessary step in the development path of EUV advanced patterning applications towards high volume manufacturing and high-NA EUV lithography.
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°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.
For semiconductor device manufacturing, line width roughness (LWR) and defect reduction 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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