Julius Joseph Santillan

Osaka University

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In situ analysis of negative-tone resist pattern formation using organic-solvent-based developer process

Applied Physics Express (2013)

Julius Joseph Santillan Keisaku Yamada Toshiro Itani

In situ resist "pattern formation" analysis during the development process using high-speed atomic force microscopy has been improved for application not only for conventional aqueous 0.26 N tetramethylammonium hydroxide (aq. TMAH), but also organic solvent n-butyl acetate (nBA) developers. Comparative investigations of resist dissolution in these developers, using the same resist material (hybrid of polyhydroxystyrene and methacrylate), showed a grainlike, uniform dissolution of the "unexposed resist film" in nBA development and uneven dissolution of the "exposed resist film" in aq. TMAH development. These results suggest the importance of dissolution uniformity in further improving the resulting pattern line width roughness.

Tetramethylammonium hydroxide

10.7567/apex.7.016501

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Citations (15)

Modeling and Simulation of Acid Diffusion in Chemically Amplified Resists with Polymer-Bound Acid Generator

Applied Physics Express (2012)

Takahiro Kozawa Julius Joseph Santillan Toshiro Itani

Chemically amplified resists with an acid generator, the anion of which is bound to the polymer through a covalent bond (anion-bound resists), are promising materials for the 16 nm node and beyond. However, their reaction mechanism is unknown. In this study, we propose a proton diffusion model for anion-bound resists. To examine the proton diffusion model, we carried out resist-patterning experiments and a simulation. The calculated latent images corresponded well to the measured line width and estimated chemical gradient. This result suggests that protons diffuse under the electric field produced by anions and induce acid-catalytic reactions in anion-bound resists.

10.1143/apex.5.074301

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Citations (6)

An investigation on "nano-swelling" phenomenon during resist dissolution using in situ high-speed atomic force microscopy

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2017)

Julius Joseph Santillan Toshiro Itani

This work focuses on the application of a high-speed atomic force microscope (HS-AFM) for the in situ observation / quantification of the resist dissolution process. Specifically, this paper discusses on the existence of what the authors refer to as "nano-swelling" which occurs in the extreme ultraviolet (EUV) exposed areas of a positive-tone chemically amplified resist, just before it dissolves into the aqueous tetramethylammonium hydroxide (TMAH) developer solution. In earlier experiments using typical EUVL resist materials (e.g. polyhydroxystyrene (PHS) polymer and hybrid PHS-methacryl polymer model resists), it was understood that nano-swelling is mainly material type-dependent. As shown in the investigations/results in this paper, nano-swelling has variations in the timing of occurrence and amount/size depending on the size of the dissolvable areas (i.e. larger dissolvable areas dissolve faster, swell more compared to smaller ones). Lastly, a comparison of surface analyses results of a resist pattern before, during, and after the occurrence of nano-swelling suggests the significant impact of these kinds of non-uniformities in the formation of line edge/line width roughness (LER/LWR).

10.1117/12.2257835

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Citations (2)

Alternative developer solution/process for EUV lithography: ethyltrimethylammonium hydroxide (ETMAH)

Julius Joseph Santillan Masahiko Harumoto Tomohiro Motono Andreia Figueiredo dos Santos Chisayo Mori

The application of the ethyltrimethylammonium hydroxide (ETMAH) as alternative developer solution for EUV lithography was investigated (compared to the tetramethylammonium hydroxide or TMAH standard developer). Early reports have shown that at a specific or optimal developer concentration of around 0.20N the ETMAH developer allows mitigation of resist-based stochastic defects (increase in stochastic defect margin) while maintaining lithographic performance. Results obtained here suggest that with the use of a non-ionic surfactant additive for the ETMAH developer solution LWR reduction was achieved (compared to TMAH). This improvement in LWR was achieved while preserving resolution, sensitivity, and stochastic defect margin.

Extreme Ultraviolet Lithography

Tetramethylammonium hydroxide

Immersion lithography

Margin (machine learning)

10.1117/12.2583753

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Citations (1)

Study on Organic Thin Film Ablation Using Femtosecond Extreme Ultraviolet Pulses

The Japan Society of Applied Physics (2017)

Kazuyuki Sakaue Masahiko Ishino Toshiro Itani Yuichi Inubushi S. Ichimaru

Extreme ultraviolet

Ultraviolet

Source

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Analysis of Outgassing from EUV Resists

Journal of Photopolymer Science and Technology (2007)

Shinji Kobayashi Minoru Toriumi Julius Joseph Santillan

Outgassing evaluations of polyhydroxystyrene (PHS) based chemically amplified EUV positive photoresist was performed. As a result, the strong dependencies of outgassing increase to various process conditions such as pre-bake temperature and time, resist film thickness and pre-exposure retarding time in vacuum were understood. Of these process conditions, the most significant process factor was known to be the variation of pre-bake temperature. It was concluded that the main cause of such variations were the effect of residual solvent in the photoresist film. From a re-analysis of the mass spectrum, outgassing components released during EUV exposure have been observed and classified into two general types of release trends; fast and slow reaction rate components. Fast reaction rate components were assumed to have originated from photoresist photo-acid generator (PAG) (48amu and 64amu). On the other hand, slow reaction rate components assumed to be mostly CxHy, have been speculated to originate from the decomposition of the photoresist protecting group after reaction with the released photoacids of PAG. Based on these results, the further analysis of photoresist outgassing release mechanisms upon EUV exposure was made possible.

Outgassing

Photoresist

Extreme Ultraviolet Lithography

10.2494/photopolymer.20.445

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Citations (2)

Stochastic effects in fabrication of 11nm line-and-space patterns using extreme ultraviolet lithography

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2014)

Takahiro Kozawa Julius Joseph Santillan Toshiro Itani

The suppression of stochastic effects such as line edge roughness (LER) and stochastic defect generation is required for the realization of high volume production of semiconductor devices with 11 nm critical dimension using extreme ultraviolet (EUV) lithography. In this study, the effect of the molecular weight and protection ratio of the resist polymer on LER and stochastic defect generation was investigated. By increasing the molecular weight, LER and the probability for the stochastic defect generation were decreased. The negative effect caused by the increase of molecular weight is the increase of the minimum block size for dissolution in the development process. By increasing the protection ratio, the similar effect was expected. However, LER and the probability for the stochastic defect generation were not significantly decreased by increasing the protection ratio because of the decrease of quantum efficiency of acid generation caused by the protection of proton sources. The development of protecting group that does not affect the quantum efficiency is essential to decrease the stochastic effects.

Extreme Ultraviolet Lithography

Extreme ultraviolet

Critical dimension

10.1117/12.2046225

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Citations (1)

Resist Patterning Characteristics using KrF Laser-ablation Process

Journal of Photopolymer Science and Technology (2019)

H. Yamaoka Julius Joseph Santillan Nobutaka Uemori Toshiro Itani

The patterning characteristics of a variety of resist material platforms were investigated using a KrF laser ablation process. The results showed that a fullerene-based resist material with a 170-nm film thickness is capable of sub-micron resolution up to 0.8 μm 1:1 lines and spaces (L/S). Moreover, using a novolac-based resist material, the dependence of laser ablation patterning performance on the resist process conditions was determined. An increase in the total exposure energy (exposure energy per pass × total number of passes) is necessary as the film thickness increases. Moreover, using the same novolac-based resist material fixed at a 5-μm film thickness, results suggested that exposure energy has a more significant impact on the effective formation of laser ablation patterns (compared to number of exposure passes). Finally, preliminary investigations using a metal resist (at a 90-nm film thickness) resulted in resolution capabilities up to 2 μm 1:1 L/S at a relatively lower total exposure energy. This showed the potential of the metal resist material for application in laser ablation patterning.

Laser Ablation

Multiple exposure

10.2494/photopolymer.32.355

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EUV resist outgassing analysis in Selete

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2008)

Julius Joseph Santillan Shinji Kobayashi Toshiro Itani

To keep in pace with the highly accelerated speed of development of EUV resists, the use of the pressure rise method in the screening of EUV resist outgassing was utilized. This method was used for its advantage of in-situ applicability and evaluation speed (short evaluation time). Both "outgassing rate" [molecules/cm2/s] and "outgassing amount" [molecules/cm2] unit conventions have been obtained. In the conference, an overview of the latest EUV resist outgassing analysis results using various EUV resists (i.e. chemical amplified, PHS, acrelate, high Ea, low Ea, negative-tone, molecular, etc.) will be discussed in detail.

Outgassing

Extreme Ultraviolet Lithography

Extreme ultraviolet

10.1117/12.771779

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Citations (7)

Feasibility study of sub-10-nm-half-pitch fabrication by chemically amplified resist processes of extreme ultraviolet lithography: II. Stochastic effects

Japanese Journal of Applied Physics (2015)

Takahiro Kozawa Julius Joseph Santillan Toshiro Itani

Line edge roughness (LER) rapidly increases in the sub-10-nm-half-pitch region of resist processes used for the fabrication of semiconductor devices. Sub-10-nm fabrication with high throughput is a challenging task. In this study, the stochastic effects (LER and stochastic defect generation) of chemically amplified resist processes in the sub-10-nm-half-pitch node were investigated, assuming the use of extreme ultraviolet (EUV) lithography. The latent images were calculated by a Monte Carlo method on the basis of the sensitization and reaction mechanisms of chemically amplified EUV resists. 7-nm-half-pitch fabrication by chemically amplified resist processes is considered to be feasible. However, significant improvement in the efficiencies of the conversion processes from optical images to resist images is required.

Extreme Ultraviolet Lithography

Extreme ultraviolet

Ultraviolet

10.7567/jjap.54.036507

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Citations (16)