Compatibility between polymethacrylate-based extreme ultraviolet resists and TiO2 area-selective deposition

Abstract

Background: 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.Aim: Evaluate the potential for area-selective deposition (ASD) to improve EUV pattern resolution (e.g., by increasing etch resistance).Approach: We evaluate thermal compatibility, atomic layer deposition growth rate, and selectivity for TiO 2 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. Results:The organic resist materials studied demonstrate thermal compatibility with TiO 2 ALD (125°C for 60 min). The TiO 2 ALD process from TiCl 4 and H 2 O proceeds readily on poly(tert-butyl methacrylate), poly(p-hydroxystyrene), and poly(p-hydroxystyrene-randommethacrylic acid) polymers, with and without PAG incorporation, in either the as-formed or EUV exposed state. However, TiO 2 is inhibited on poly(cyclohexyl methacrylate). Conclusions:We demonstrate that as-formed EUV resists can serve as either the growth or nongrowth surface during TiO 2 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.

Enhancing Performance and Function of Polymethacrylate Extreme Ultraviolet Resists Using Area-Selective Deposition

“…Lines are drawn as guides to the eye. Data points corresponding to TiO 2 growth rate on SiO 2 in (a) and (b) are reproduced from refs , .…”

“…After the PEB (or development step if applicable), wafers were cleaved into coupons based on EUV exposure status for further experiments. In our previous work, we demonstrated minimal change to surface WCA for unexposed resist regions before and after development . Therefore, in this study, the unexposed resist regions without development are used to represent unexposed regions after the full lithographic process (i.e., including development).…”

“…In this scenario, the patterned resist is modified to improve etch resistance and mitigate pattern collapse, thereby enabling the use of thin resist materials . For example, metal oxides have demonstrated higher etch resistance than traditional organic resists and are a good candidate for resist hardening applications. ,, As shown in Figure c, two approaches for resist hardening include ASD of an etch resistant layer on a patterned resist (in which case the resist serves as the growth surface and rapid nucleation is desirable) , and selective reactant infiltration into the patterned resist (which takes advantage of small precursors selectively diffusing into a polymer). − In either case, the reaction can proceed on the as-prepared resist pattern or after exposure to a nucleation inhibitor. , The selective infiltration approach introduces a metal oxide into the resist and may have the additional benefit of not substantially affecting the pattern critical dimension (CD) …”

“…Another key consideration for integrated ASD-EUV is that the process temperature required for ASD must be low enough, typically ≲200 °C, to maintain the chemical integrity of the resist . Thus, additional research efforts are needed to facilitate ASD integration with thin, (i.e., <50 nm) commercially relevant resist layers …”

“…32 For example, metal oxides have demonstrated higher etch resistance than traditional organic resists and are a good candidate for resist hardening applications. 5,18,19 As shown in Figure 1c, two approaches for resist hardening include ASD of an etch resistant layer on a patterned resist (in which case the resist serves as the growth surface and rapid nucleation is desirable) 32,33 and selective reactant infiltration into the patterned resist (which takes advantage of small precursors selectively diffusing into a polymer). 34−36 In either case, the reaction can proceed on the as-prepared resist pattern or after exposure to a nucleation inhibitor.…”