Decomposition processes of photoresist polymers by H atoms produced on hot wire surfaces

Umemoto, Hironobu; Kato, Teruto; Takiguchi, Masayuki; Takagi, Seiji; Horibe, Hideo

doi:10.1016/j.tsf.2016.12.013

Cited by 7 publications

(6 citation statements)

References 26 publications

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“…The etch reactions of PMMA under a flux of H atoms have been studied in-depth by using mass spectroscopy 19 . The major decomposition products of a PMMA film at 147 ∘ C were highlighted as being essentially methane and CO, therefore emphasizing the following reaction process…”

Section: Resultsmentioning

confidence: 99%

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Reactive plasma cleaning and restoration of transition metal dichalcogenide monolayers

et al. 2021

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The cleaning of two-dimensional (2D) materials is an essential step in the fabrication of future devices, leveraging their unique physical, optical, and chemical properties. Part of these emerging 2D materials are transition metal dichalcogenides (TMDs). So far there is limited understanding of the cleaning of “monolayer” TMD materials. In this study, we report on the use of downstream H2 plasma to clean the surface of monolayer WS2 grown by MOCVD. We demonstrate that high-temperature processing is essential, allowing to maximize the removal rate of polymers and to mitigate damage caused to the WS2 in the form of sulfur vacancies. We show that low temperature in situ carbonyl sulfide (OCS) soak is an efficient way to resulfurize the material, besides high-temperature H2S annealing. The cleaning processes and mechanisms elucidated in this work are tested on back-gated field-effect transistors, confirming that transport properties of WS2 devices can be maintained by the combination of H2 plasma cleaning and OCS restoration. The low-damage plasma cleaning based on H2 and OCS is very reproducible, fast (completed in a few minutes) and uses a 300 mm industrial plasma etch system qualified for standard semiconductor pilot production. This process is, therefore, expected to enable the industrial scale-up of 2D-based devices, co-integrated with silicon technology.

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Section: Resultsmentioning

confidence: 99%

“…In downstream plasma configuration, only long-lived species, namely hydrogen atoms, are allowed to interact with the treated surface. Reactive H atoms are efficient for chemical etching of various polymers 13,18,19 . However, atomic hydrogen is also known to be reactive towards TMDs.…”

Section: Introductionmentioning

confidence: 99%

Reactive plasma cleaning and restoration of transition metal dichalcogenide monolayers

et al. 2021

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“…The reaction between benzene rings and H radicals must be the rate-determining step in the removal processes [13,14]. According to the theoretical approach by Umemoto et al [21], at least two H radicals must be involved in the decomposition of novolak. After the addition of two H radicals to the benzene ring, the ring opening becomes energetically possible.…”

Section: Resultsmentioning

confidence: 99%

Effects of Nitrogen Dilution on the Photoresist Removal Rate by Hydrogen Radicals

Yamamoto

Nishioka

Akita

et al. 2020

J. Photopol. Sci. Technol.

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We have previously demonstrated that photoresist removal rate comparable to oxygen plasma is accomplished by optimizing the removal conditions with H radicals produced on hot metal filament surfaces from H 2 /N 2 mixtures (H 2 :N 2 = 10:90 vol%). N 2 gas was used to dilute the concentration of the H 2 gas and to reduce the risk of explosion. However, it is not clear how the dilution of H 2 by N 2 affects the removal rate. In this paper, we examined the relationship between the removal rate and the H 2 content; the flow rate ratio of H 2 to H 2 +N 2. The removal rate increased with increasing the H 2 content. In addition, the removal rate increased with increasing the substrate temperature according to an Arrhenius equation, when the H 2 content was over 90%. However, below 60%, the removal rate decreased with increasing the temperature over 230 ± 5 °C. Denaturation of photoresist, e.g. hardening and/or crosslinking, may be induced by substrate heating when the H-radical density is low. The removal rate decreases not only by the deficiency of H radicals but also by the denaturation of films in H 2 /N 2 mixed systems.

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“…The reaction between benzene rings and H radicals must be the rate-determining step in the removal processes. According to Umemoto et al [23], at least two H atoms must be involved in the decomposition of novolak theoretically. After the addition of two H atoms to the benzene ring, the ring opening becomes energetically possible.…”

Section: Resultsmentioning

confidence: 99%

Relationship between Oxygen Additive Amount and Photoresist Removal Rate Using H Radicals Generated on an Iridium Hot-Wire Catalyst

Yamamoto

Shiroi

Shikama

et al. 2019

J. Photopol. Sci. Technol.

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We examined an environmentally friendly photoresist removal method using radicals produced by decomposing mixtures of hydrogen and oxygen on a hot iridium catalyst. We earlier reported that the decomposition of photoresists was hastened by adding oxygen gas to a hydrogen flow using a tungsten hot-wire catalyst. The rate increased with the oxygen additive amount up to about 1.0% and then decreased gradually. The decrease is caused by the catalytic poisoning of O atoms on the catalyst surface because of its poor oxidation resistance. In present study, we show that oxygen addition without catalytic poisoning is effective to increase the decomposition rate. The poisoning can be avoided by using an Ir catalyst. The decomposition rate increased with the substrate temperature. The rate also increased rapidly with increasing amounts of added oxygen to 1.0% and then the increase became more gradual. OH radicals must play an important role to hasten the decomposition reactions.

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Decomposition processes of photoresist polymers by H atoms produced on hot wire surfaces

Cited by 7 publications

References 26 publications

Reactive plasma cleaning and restoration of transition metal dichalcogenide monolayers

Reactive plasma cleaning and restoration of transition metal dichalcogenide monolayers

Effects of Nitrogen Dilution on the Photoresist Removal Rate by Hydrogen Radicals

Relationship between Oxygen Additive Amount and Photoresist Removal Rate Using H Radicals Generated on an Iridium Hot-Wire Catalyst

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