Investigation of the exposure and bake of a positive acting resist with chemical amplification

Ferguson, Richard A.; Spence, Chris; Reichmanis, Elsa; Thompson, L. F.; Neureuther, Andrew R.

doi:10.1117/12.20086

Cited by 17 publications

(8 citation statements)

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“…Several features that were observed in other studies are evident in our data. When the data are reported on a linear time scale (Figure a), it appears that the reaction is self-limiting with a maximum deprotection level that depends on acid concentration. ,− However, on a logarithmic time scale, it appears that the deprotection reaction continues with an extremely slow rate. (The increase in data scatter at long reaction times was discussed in the Experimental Procedures.)…”

Section: Resultsmentioning

confidence: 99%

Reaction Kinetics in Acid-Catalyzed Deprotection of Polymer Films

et al. 2012

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A quantitative description of kinetics in acid-catalyzed polymer deprotection reactions requires proper identification of the controlling mechanisms. We examined the acid-catalyzed deprotection of a glassy poly(4-hydroxystyrene-co-tert-butyl acrylate) resin using infrared absorbance spectroscopy and stochastic simulations. We interpret experimental data with a model that explicitly accounts for acid transport, where heterogeneities at local length scales are introduced through a nonexponential distribution of waiting times between successive hopping events. A subdiffusive behavior with long-tail kinetics predicts key attributes of the observed deprotection rates, such as a fast initial deprotection, slow conversion at long times, and a nonlinear dependence on acid loading. Most importantly, only two parameters are introduced to offer a near-quantitative description of deprotection levels at low acid loadings and short times. The model is extended to high acid loadings and long times by incorporating a simple acid depletion model based on mutual encounters. Our study suggests that macroscopic deprotection rates are controlled by acid transport in the glassy deprotected polymer, which presents with a strongly non-Fickian behavior.

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Section: Resultsmentioning

confidence: 99%

Reaction Kinetics in Acid-Catalyzed Deprotection of Polymer Films

et al. 2012

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“…It was proposed that this enhancement, which is observed in several CAR resins with volatile protecting groups, arises from a short-lived increase in free volume upon reaction. ,,− However, this concept is inconsistent with measurements of PBOCSt deprotection, which show the same timescales for reaction and polymer densification . Another common approach in reaction–diffusion models is the inclusion of additional processes describing an acid loss. ,, Acid loss is often presented as a “trapping process” attributed to either contaminants or strong local interactions with the polymer, such as hydrogen bonding, and has been used in models of several CAR chemistries. ,,,− …”

Section: Introductionmentioning

confidence: 99%

“…21 Another common approach in reaction−diffusion models is the inclusion of additional processes describing an acid loss. 11,22,23 Acid loss is often presented as a "trapping process" attributed to either contaminants or strong local interactions with the polymer, such as hydrogen bonding, and has been used in models of several CAR chemistries. 11,19,20,22−26 The proposed phenomenological processes are difficult to validate because few experimental techniques can directly probe molecular-scale phenomena such as acid−anion motion, ion−ion interactions, or ion−polymer interactions.…”

Section: ■ Introductionmentioning

confidence: 99%

Ion Diffusion in Chemically Amplified Resists

et al. 2021

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The acid-catalyzed deprotection of glassy polymer resins is an important process in semiconductor lithography. Studies have shown that the reaction kinetics in these materials is controlled by slow diffusion of the acid−anion catalyst, but trends deviate from models of a first-order reaction coupled to a composition-invariant Fickian diffusivity. We present a concerted experimental and computational effort to examine catalyst diffusion in a model resin of poly(4-hydroxystyrene-co-tert-butyl acrylate-co-styrene), or P-(HOSt-tBA-St), which is deprotected in the presence of an acid catalyst to poly(4-hydroxystyrene-co-acrylic acid-co-styrene), or P(HOSt-AA-St). We employed an inert catalyst analogue to examine long-time ion dynamics in both terpolymers with atomistic molecular dynamics simulations and compared the calculated Fickian diffusivities with direct measurements of ion diffusion fronts using time-of-flight secondary ion mass spectrometry. Our results demonstrate that ion diffusivities in P(HOSt-tBA-St) and in P(HOSt-AA-St) are similar near and below the glass transition, consistent with a diffusion process that is dominated by interactions with the polar HOSt units. We then compared the bulk reaction kinetics measured by Fourier-transform infrared spectroscopy with reaction kinetics obtained using mesoscopic reaction−diffusion models. We found that initial reaction kinetics is significantly accelerated compared to predictions based on the long-time ion diffusivities of our inert system. This study highlights the potential of atomistic modeling coupled with targeted experiments for interrogating the physical and chemical processes that control pattern formation in next-generation lithographic materials.

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“…A nonlinear increase in reaction rates with acid concentration has been observed, and when combined with acid diffusion in simulation shows a tendency to reinforce rather than to remove than standing wave effects [4]. In order to explain the absence of standing waves in resist profiles, a locally increased diffusion related to the exposure and or the reaction state is a plausible alternative mechanism.…”

Section: Diffusion Models and Simulationmentioning

confidence: 96%

Diffusion effects in chemically amplified deep-UV resists

Zúñiga

Tomacruz

Neureuther

1994

Advances in Resist Technology and Processing XI

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Evidence from simulation, lmewidth measurements is presented which suggests that a type II diffusion front is moving through positive tone t-BOC material during post exposure bake. A steady increase in linespace of 50 nm/mm is observed in IBM APEX-E and even faster rates can be found in Apex-M. The converse is observed in negative resist systems, which evidence slower linewidth dependencies. The simultaneous reaction and 3-D deprotection dependent diffusion simulation was carried out with a massively parallel approach. In addition, two-dimensional diffusion effects were studied with a test structures obtained with a super resolution phase shift mask.

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Investigation of the exposure and bake of a positive acting resist with chemical amplification

Cited by 17 publications

References 0 publications

Reaction Kinetics in Acid-Catalyzed Deprotection of Polymer Films

Reaction Kinetics in Acid-Catalyzed Deprotection of Polymer Films

Ion Diffusion in Chemically Amplified Resists

Diffusion effects in chemically amplified deep-UV resists

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