Dr. Vijay Surla Profile

Dr. Vijay Surla

at Univ of Illinois

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Publications (5)

Proceedings Article | 20 March 2010 Paper

Debris measurement at the intermediate focus of a laser-assisted discharge-produced plasma light source

J. Sporre, V. Surla, M. Neumann, D. Ruzic, L. Ren, F. Goodwin

Proceedings Volume 7636, 763611 (2010) https://doi.org/10.1117/12.846590

KEYWORDS: Plasma, Extreme ultraviolet, Tin, Argon, Microchannel plates, Ions, Sensors, Electrodes, Diagnostics, Silicon

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Proceedings Article | 20 March 2010 Paper

Removal of carbon and nanoparticles from lithographic materials by plasma assisted cleaning by metastable atom neutralization (PACMAN)

W. Lytle, R. Lofgren, V. Surla, M. Neumann, D. Ruzic

Proceedings Volume 7636, 76360O (2010) https://doi.org/10.1117/12.846282

KEYWORDS: Plasma, Helium, Ions, Carbon, Semiconducting wafers, Photomasks, Chemical species, Sputter deposition, Electrons, Particles

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System cleanliness is a major issue facing the lithographic community as the prospects of integrating EUV lithography into integrated circuit manufacturing progress. Mask cleanliness, especially of particles in the sub-micron range, remains an issue for the implementation of EUV lithography since traditional mask cleaning processes are limited in their ability to remove nanometer scale contaminants. The result is lower wafer throughput due to errors in pattern transfer to the wafer from the particulate defects on the mask. Additionally, carbon contamination and growth on the collector optics due to energetic photon interactions degrade the mirror and shortens its functional life. Plasma cleaning of surfaces has been used for a variety of applications in the past, and now is being extended to cleaning surfaces for EUV, specifically the mask and collector optics, through a process developed in the Center for Plasma-Material Interactions (CPMI) called Plasma Assisted Cleaning by Metastable Atom Neutralization (PACMAN). This process uses energetic neutral atoms (metastables) in addition to a high-density plasma (Te ≈ 3 eV and ne ≈ 10¹⁷ m^-3) to remove particles. The PACMAN process is a completely dry process and is carried out in a vacuum which makes it compatible with other EUV related processing steps. Experiments carried out on cleaning polystyrene latex (PSL) nanoparticles (30 nm to 500 nm) on silicon wafers, chrome coated mask blanks, and EUV mask blanks result in 100 % particle removal with a helium plasma and helium metastables. Removal rates greater than 20 nm/min have been achieved for PSL material. Similar removal rates have been achieved for the PACMAN cleaning of carbon from silicon wafers (simulating collector optic material) with 100% removal with helium plasma and helium metastables. The PACMAN cleaning technique has not caused any damage to the substrate type being cleaned either through roughening or surface sputtering. Current results of cleaning various particle types from surfaces through the PACMAN process are presented.

Proceedings Article | 20 March 2010 Paper

Sn debris cleaning by plasma in DPP EUV source systems for HVM

H. Shin, V. Surla, M. Neumann, D. Ruzic

Proceedings Volume 7636, 76360B (2010) https://doi.org/10.1117/12.846359

KEYWORDS: Plasma, Tin, Chlorine, Extreme ultraviolet, Etching, Ions, Mirrors, Reactive ion etching, Contamination, Plasma etching

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The tin (Sn) debris contamination is one of the technical challenges for the development of high power EUV light source with Sn fuel with a long lifetime of EUV collectors. The debris mitigation techniques (DMTs) can considerably minimize the Sn debris coming out of the source thereby reducing the need or effort for cleaning. However, for HVM, which requires higher EUV power output than today, it is questionable if the DMTs alone will completely eliminate the Sn contamination. Besides, at abnormal instances, we also need to clean thick Sn debris from the mirror surface. For this purpose, the Center for Plasma-Material Interactions (CPMI) at University of Illinois at Urbana-Champaign has developed a plasma-based Sn cleaning method using chlorine plasma with densities and temperature around ~9×10⁹/cm³ and ~ 4 eV respectively. From the previous studies at CPMI, it was shown that chlorine plasma etching can remove Sn debris from Ru mirror surface in a fast (> 400 nm/min) and in situ manner. In this study, we applied the same method to clean Sn contamination on the mock-up collector in our XTS13-35 DPP EUV source system. The mock-up is made of two shells with different gap widths (4 cm, 7.5 cm and 10 cm) in similar size with the actual collector optic. The cleaning rate at different locations on the mockup was experimentally investigated, and it was found that the cleaning rates vary largely with the distance from the chlorine plasma in the range of 20 - 100 nm/min. In addition, a simple analytical model to predict the cleaning rate was developed based on the plasma-surface reactions and the plasma transport. The model describes how plasma transport, chlorine radical distribution and pumping flow affect the Sn cleaning rate with chlorine plasma. Finally, the model is then compared to the experimental results and validated. Based on the knowledge of chlorine plasma and Sn interactions obtained in this study, a remote plasma cleaning technique was also investigated and the results obtained therein are presented. The experimental results along with the model predictions will help design an integrated cleaning system for collector optic in the high power EUV source system for HVM.

Proceedings Article | 18 March 2009 Paper

Measurement of particle flux at the intermediate focus of a DPP source

J. Sporre, R. Raju, D. Ruzic, V. Surla, F. Goodwin

Proceedings Volume 7271, 727137 (2009) https://doi.org/10.1117/12.814225

KEYWORDS: Ions, Sensors, Particles, Contamination, Extreme ultraviolet, Silicon, Carbon, Plasma, Silicon carbide, Oxygen

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Proceedings Article | 4 December 2008 Paper

Removal of particles from lithographic masks through plasma-assisted cleaning by metastable atomic neutralization

W. Lytle, D. Szybilski, C. Das, R. Raju, V. Surla, M. Neumann, D. Ruzic

Proceedings Volume 7140, 71401S (2008) https://doi.org/10.1117/12.804704

KEYWORDS: Plasma, Particles, Helium, Semiconducting wafers, Photomasks, Atmospheric particles, Silicon, Lithography, Chemical species, Extreme ultraviolet lithography

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