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.
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.
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