Science Papers

Publications about contamination and the effectiveness of the Evactron system

THE SCIENTIFIC BACKGROUND

In SEMs, FIBs, and TEMs, contamination is a serious problem for specimen analysis and the production of high-resolution images. Beam-induced carbonaceous material is deposited on the region under study, causing loss of resolution. Hydrocarbon contamination causes the image darkening or “Black Square” in a typical SEM image. The Evactron De-Contaminator removes hydrocarbon contamination from electron microscopes. A radio frequency (RF) generated plasma is attached to the microscope vacuum chamber. Room air or other oxygen containing gas passes through the plasma, producing oxygen radicals in situ. These radicals clean organic contaminants from the interior of vacuum systems and sample surfaces. The oxygen radicals decompose carbon-containing material into H2O, CO, and CO2, which are evacuated from the system.

Application of Plasma Cleaning Technology in Microscopy

Tom Levesque, Technology Business Consulting and Jezz Leckenby, Talking Science

The cleanliness of specimen surfaces and the high vacuum electron microscope environments in which these surfaces are studied or processed have never been more critical than they are today with examination and fabrication nearing the atomic level. Routine manufacturing at the scale required for nanotechnology demands pristine and controlled surfaces in order to create the desired structures. Modern electron and ion microscopes are equipped with sophisticated vacuum systems and can provide these conditions, but maintaining cleanliness over time may be more difficult. One of the ways that scientists have been able to achieve these remarkably unadulterated surfaces has been to subject their samples and microscopes to cleaning by various plasma technologies.

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Carbon Contamination removal in Large Chambers with Low-Power Downstream Plasma Cleaning

Christopher G. Morgan and Ronald Vane, XEI Scientific, Inc., Redwood City, CA
Paper presented at SPIE Advanced Lithography Conference Feb. 14, 2012, San Jose CA.

Many lithographic tools require carbon-free vacuum environments. A commercially available low-power (<20W) downstream plasma system which produces oxygen radicals in the 0.2-0.6 Torr pressure range has been shown to be effective in removing carbon contamination from standard SEM and FIB tools. However, in larger systems such as wafer or mask inspection tools the extent of cleaning in this pressure range is limited. A new downstream plasma system optimized for larger chambers has been developed which operates at higher power and lower pressure. Cleaning rates of over 1 nm/minute have been measure from over 0.5 m away from the plasma source.

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Contamination Removal Rates Improved by New Impedance Matching Network for the Evactron® De-Contaminator

Christopher G. Morgan and Ronald Vane, XEI Scientific, Inc., Redwood City, CA
Paper presented at SPIE Advanced Lithography Conference Feb. 14, 2012, San Jose CA.

Many lithographic tools require carbon-free vacuum environments. A commercially available low-power (<20W) downstream plasma system which produces oxygen radicals in the 0.2-0.6 Torr pressure range has been shown to be effective in removing carbon contamination from standard SEM and FIB tools. However, in larger systems such as wafer or mask inspection tools the extent of cleaning in this pressure range is limited. A new downstream plasma system optimized for larger chambers has been developed which operates at higher power and lower pressure. Cleaning rates of over 1 nm/minute have been measure from over 0.5 m away from the plasma source.

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Using Thickness Monitor to Measure Contaminant Removal by Evactron Cleaning as a Function of Operating Parameters

Christopher G. Morgan, Mark M. Gleason and Ronald Vane, XEI Scientific, Inc., Redwood City, CA
Poster Presentations at Microscopy and Microanalysis Meeting, August, 2007, Ft. Lauderdale, FL

Quartz crystal microbalances (QCMs) are a standard tool for vacuum deposition measurements. They can also be adapted to measure contamination removal by plasma cleaning. Here, they are used to record a thickness loss rate of an oil layer previously deposited on their surface; this loss rate is a measure of the cleaning effectiveness of the Evactron Decontaminator.

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Quantification of Contamination Using Quartz Crystal Thickness Monitors

Christopher G. Morgan, Mark M. Gleason and Ronald Vane, XEI Scientific, Inc., Redwood City, CA
Poster Presentations at Microscopy and Microanalysis Meeting, August, 2007, Ft. Lauderdale, FL

Quartz crystal microbalances (QCMs) are a standard tool for vacuum deposition measurements. They can also be adapted to measure contamination removal by plasma cleaning. Here, they are used to record a thickness loss rate of an oil layer previously deposited on their surface; this loss rate is a measure of the cleaning effectiveness of the Evactron Decontaminator.

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Effect of Cleaning Parameters on Cleaning Effectiveness in a SEM Equipped with an Oxygen Plasma Etching Device

R. Garcia*, A.D. Batchelor*, C.B. Mooney*, A.D. Garetto*, V.L. Carlino**, R. Vane**, and D.P. Griffiths *Materials Science and Engineering Department and Analytical Instrumentation Facility, North Carolina State University, Raleigh, NC; **XEI Scientific, Redwood City, CA 94063
Poster Presentation at Microscopy and Microanalysis Meeting, August, 2007, Ft. Lauderdale, FL

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Immobilization and Removal of Hydrocarbon Contamination Using the Evactron®De-Contaminator

Ronald Vane, XEI Scientific, Inc., Redwood City, CA
Presentation at Microscopy and Microanalysis Meeting, July-August, 2006, Chicago, IL

Comparison of Residual Gas Analysis results on the removal of volatile components and visual observance of the removal of Hydrocarbon films indicates that the immobilization of Hydrocarbons on surfaces by polymerization using the Evactron De-Contaminator is also an important mechanism for reducing contamination interference with imaging in electron microscopy.

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Environmental Contamination Sources and Control in High Resolution Scanning Electron Microscopy

Ronald Vane and Vince Carlino, XEI Scientific, Inc., Redwood City, CA
Presentation at Microscopy and Microanalysis Meeting, August, 2005, Honolulu, HI

Hydrocarbon (HC) background and contamination is hard to avoid in our carbon based world. Even with the most careful handling carbon contamination artifacts from Airborne Molecular Contamination (AMC) can creep in and interfere with imaging and measurement in e-beam instruments. The Evactron De-Contaminator made by XEI Scientific is a tool that actively removes HC from the vacuum system and specimens within it to prevent these problems.

(PDF document unavailable.)

Vapor-Phase Cutting of Carbon Nanotubes Using a Nanomanipulator Platform

Vladimir Mancevski, President and CTO, Xidex Corporation; Philip D. Rack, Professor, The University of Tennessee at Knoxville
Presented at the 2010 Materials Science and Technology Conference, October 2010, Houston, TX

Xidex has developed the NanoBot® nanomanipulator, which can be used as a vapor-phase cutting system to etch carbon nanotubes. They report (see slide 19) that plasma cleaning using the Evactron De-Contaminator inside the SEM chamber can reduce competitive carbon deposition and enhance etching.

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Improved Carbon Analysis with Evactron Plasma Cleaning

Pierre Rolland*, Vincent L. Carlino**, and Ronald Vane**, *Alprimage, 11 rue de Savoie, 91940 Les Ulis, France, **XEI Scientific, 1735 East Bayshore Rd., Suite 29A, Redwood City, CA 94063, USA
Presentation at Microscopy and Microanalysis Meeting, August, 2004, Savannah, GA

A complete paper on EDS analysis of carbon.

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Effect of Evactron® Cleaning on EBSD Detector Phosphor Screens

Mark Nave* and Andrew Sullivan**, *Microanalysis Consulting Pty. Ltd., St Albans Park, Victoria, Australia
**Centre for Material and Fibre Innovation, Deakin University, Geelong, Victoria, Australia

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A Study of the Effects of Evactron® Plasma Cleaning on X-ray Windows

Ronald Vane*, Christine Roberts**, and Vince Carlino* *XEI Scientific, Inc., Redwood City, CA 94063 **Formerly with MOXTEK, Inc., Orem, UT 84057
Presentation at Microscopy and Microanalysis Meeting, August, 2004, Savannah, GA

A complete paper showing that long term cleaning of ultra thin windows (UTW) does not cause window failure.

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Minimization of Hydrocarbon Accumulation on Nanomanipulator Probe Tips

G. McMahon,* Christopher G.. Morgan,** and Ronald Vane** *Nanofabrication Cleanroom Facility, Boston College, Newton, MA 02459, **XEI Scientific, Inc., Redwood City, CA 94063
Poster Presentation at the 2010 Kleindiek User’s Group Meetand and the Microscopy and Microanalysis Meeting, August 2010, Portland, OR

A very positive effect of Evactron downstream plasma cleaning in the prevention of hydrocarbon buildup in nanomanipulator probe tips is reported in this poster.

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Non-Destructive Cleaning of Carbon Nanotube Surfaces: Removal of Organic Contaminants and Chemical Residue with Oxygen Radicals

Mihail P. Petkov, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA
Presentation at Microscopy and Microanalysis Meeting, August, 2004, Savannah, GA

Oxygen radicals (OR) have been used as a surface cleaning method for a diverse range of materials. However, the application of OR cleaning to graphite and carbon nanotubes is not straightforward, as oxygen plasma is known to ash both forms of carbon. This work demonstrates a successful OR cleaning of surface organic contaminants (most likely hydrocarbons from the air), as well as chemical residue from the fabrication process, without inducing microstructural changes visible by SEM. An Evactron Decontaminator was used for the study.

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Removal of Carbon Contamination using Hydrogen with Low-Power Downstream Plasma Cleaning

C. G. Morgan and R. Vane, XEI Scientific, Inc., Redwood City, CA
Poster Presentation at SPIE Advanced Lithography Conference, March 2011, San Jose, CA

Carbon contamination on extreme ultraviolet (EUV) optics reduces their reflectivity. The use of a commercially available low power downstream plasma cleaner using room air has been shown to be effective in removing carbon contamination from EUV optics. However,there is concern that removal of carbon contamination by oxidation may damage the capping layers of the optics. In particular, ruthenium capping layers may be susceptible to reaction with oxygen radicals. The previous experiments with low power downstream plasma were done on silicon capped EUV optics. In this paper, the use of gases other than room air, such as hydrogen with low power downstream plasma cleaning is explored to determine its effectiveness by using customized quartz crystal monitors.

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Comparing the Effects of Different Gas Mixtures and Vacuum Chamber Geometries on the Evactron Cleaning Process

Christopher G. Morgan and Ronald Vane, XEI Scientific, Inc., Redwood City, CA
Poster Presentation at Microscopy and Microanalysis Meeting, August 2008, Albuquerque, NM.

Using a quartz crystal microbalance (QCM), the effectiveness of the Evactron® process has been quantified in this study, as a function of cleaning parameters such as chamber pressure during cleaning, RF power, and distance from the plasma source. The QCM measurements can now be extended in order to consider the effect of different gas mixtures and chamber geometries on cleaning.

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The Use of Oxygen in SEM Plasma Cleaning Equipment

Thomas O. Mueller, J. Cowan, and E. Swanson, ON Semiconductor, Gresham Failure Analysis Laboratory, Gresham, OR
Poster Presentation at Microscopy and Microanalysis Meeting, August, 2007, Ft. Lauderdale, FL

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Remote Plasma Cleaning from a TEM Sample Holder with an Evactron De-Contaminator

Christopher G. Morgan, David Varley, and Ronald Vane, XEI Scientific, Inc., Redwood City, CA
Poster Presentation at Microscopy and Microanalysis Meeting, August 2010, Portland, OR

A new method for using the Evactron D-C to clean TEMs is reported. The RF electrode used to create the oxygen radicals is now mounted on the end of a TEM sample rod. The impedance matching network and gas delivery hardware are placed on the other end of the sample rod, which is hollow to allow oxygen containing gas to reach the electrode.

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Contamination-Free Transmission Electron Microscopy for High-Resolution Carbon Elemental Mapping of Polymers

Shin Horiuchi*, Takeshi Hanada**, Masaharu Ebisawa**, Yasuhiro Matsuda***, Motoyasu Kobayashi***, and Atsushi Takahara***,*AIST, Ibaraki, Japan, **Consulting Zero Loss Imaging, Tokyo, Japan ***Institute for Materials Chemistry and Engineering, Fukuoka, Japan
ACS Nano, 2009, 3(5), pp 1297-1304 Microscopy and Microanalysis Meeting Aug 2008

This study utilizes the Evactron® D-C for TEMs. The “contamination-free TEM” allowed researchers to accomplish high-resolution carbon elemental mapping by energy-filtered transmission electron microscopy (EFTEM) on the nanostructure of soft materials. In addition, this study illustrates that although TEM cryo-observation is known to be effective in reducing specimen damage, it was not observed to help in carbon mapping, suggesting that the cooling of the specimen may actually increase the contamination deposition rate. In the case of polymers, the detection of carbon is much simpler than those of other light elements because of its high content. Being able to do carbon analysis by elemental mapping and EELS with high spatial resolution without problematic contamination could lead to improvements for various soft-material nanoanalyses by EFTEM. This study suggests that the analytical technique utilizing the “contamination-free TEM” also offers possibilities in studies requiring extended exposure time of the electron beam, such as EELS, nanobeam diffraction and electron tomography.

View article/abstract here.

Cleaning of Capped Multi-Layer Samples and Cleaning with Hydrogen using the Evactron® De-Contaminator

Christopher G. Morgan and Ronald Vane*, XEI Scientific, Inc., 1755 E. Bayshore Blvd., Redwood City, CA
Presentation at the EUV Lithography Workshop, June 2011, Maui, Hawaii

Carbon contamination on extreme ultraviolet (EUV) optics reduces their reflectivity. Further studies of the effect cleaning multilayer blanks capped with either silicon or ruthenium by the Evactron system are presented. Room air and argon/oxygen mixtures are used as the cleaning gas. EUV reflectivity of the blanks and surface roughness are measured post cleaning to determine if the cleaning process is both effective and not harmful. Preliminary data shows that the oxygen mixtures are very effective at removing PMMA resist from a silicon wafer. Additionally the use of hydrogen gas with the Evactron De-Contaminator is explored. Optical emission spectra of the plasma show that hydrogen radicals are created by the Evactron system. Cleaning effectiveness can be determined by using quartz crystal microbalances. The hydrogen atoms remove carbon contamination with maximum cleaning occurring at 100 mTorr chamber pressure. Rates around 1 nm per minute have been measured when the Evactron system is 15 cm from the quartz crystal microbalance.

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Removal of Surface Contamination from EUV Mirrors using Low-Power Downstream Plasma Cleaning

Christopher G. Morgan*, Patrick P. Naulleau**, Senajith B. Rekawa**, Paul E. Denham**, Brian H. Hoef**, Michael S. Jones**, and Ronald Vane*, *XEI Scientific, Inc., 1755 E. Bayshore Blvd., Redwood City, CA, **Center for X-Ray Optics (CXRO), Lawrence Berkeley National Laboratory, Berkeley, CA
Poster Presentation at SPIE Advanced Lithography Conference, February 2010, San Jose, CA

The problem of carbon contamination on extreme ultraviolet (EUV) optics, causing unacceptably low reflectivity in mirrors, must be solved before industry will adopt the technology on a production scale. The quantity of oxygen radicals produced by the low-power downstream plasma cleaner is sufficient to remove contamination from EUV optics as demonstrated by the experiments. Additionally, EUV reflectance measurements show that this method of cleaning optics does not reduce the reflectivity of the optic through formation of an oxide on the capping layer of the optic.

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Contamination Specification for Dimensional Metrology SEMs

András E. Vladár, K. P. Purushotham and Michael T. Postek, NIST, Gaithersburg, MD
Presented at SPIE Advanced Microlithograpy Feb 2008, San Jose, CA

Electron beam-induced contamination is becoming one of the most bothersome problems of the scanning electron microscopes. Even in clean-vacuum instruments it is possible that the image gradually darkens because a polymerized hydrocarbon layer with low secondary electron yield is deposited. This contamination layer can get so thick that it changes the size and shape of the small structures of current and future state-of-the art ICs. This greatly disturbs the measurement process and the erroneous results can lead to wrong process control decisions. NIST has developed cleaning procedures and a viable contamination specification that offer an effective solution for this problem.

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A Study of the Effectiveness of the Removal of Hydrocarbon Contamination by Oxidative Cleaning Inside the SEM

Neal Sullivan*, Tung Mai*, Scott Bowdoin*, and Ronald Vane**, *Schlumberger Technologies, 45 Winthrop St., Concord, MA **XEI Scientific, Inc., Redwood City, CA
Presentation at Microscopy and Microanalysis Meeting, August, 2002, Quebec City, Canada (Microscopy& Microscroanalysis Vol. 8, Supplement 2, 720CD)

A complete paper with CD SEM data.

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Active Monitoring and Control of Electron Beam Induced Contamination

András E. Vladár*, Michael T. Postek* and Ronald Vane**, *National Institute of Standards and Technology, Gaithersburg, MD **XEI Scientific, Inc., Redwood City, CA
Presentation at SPIE Microlilthography Conference Feb 27-28, 2001; Proc SPIE, Vol. 4344(2001): 835.

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Direct Bandgap Transition in Many-Layer MoS 2 by Plasma-Induced Layer

Rohan Dhall , Mahesh R. Neupane , Darshana Wickramaratne , Matthew Mecklenburg , Zhen Li , Cameron Moore , Roger K. Lake, and Stephen Cronin

2D materials, such as graphene and few-layer transition metal dichalcogenides (TMDCs), have attracted great research interest in the past decade, since mechanical exfoliation of these materials from their 3D bulk counterparts was demonstrated.

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Creating nanoporosity in silver nanocolumns by direct exposure to radio-frequency air plasma

Abdel-Aziz El Mel,  Nicolas Stephan,  Jonathan Hamon,  Damien Thiry, Adrien Chauvin, Meriem Chettab, Eric Gautron, Stephanos Konstantinidis, Agnès Graniera  and Pierre-Yves Tessiera

Nanoporous materials are of great importance for a broad range of applications including catalysis, optical sensors and water filtration. Although several approaches already exist for the creation of nanoporous materials, the race for the development of versatile methods, more suitable for the nanoelectronics industry, is still
ongoing.

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Strong Circularly Polarized Photoluminescence from Multilayer MoS2 2 Through Plasma Driven Direct-Gap Transition

Rohan Dhall, Kyle Seyler, Zhen Li,Darshana Wickramaratne, Mahesh R. Neupane, Ioannis Chatzakis, Ewa Kosmowska, Roger K. Lake, Xiaodong Xu, and Stephen Cronin

ABSTRACT: We report circularly polarized photoluminescence spectra taken from few layer MoS2 after treatment with a remotely generated oxygen plasma. Here, the oxygen plasma decouples the individual layers in MoS2 by perturbing the weak interlayer van der Waals forces without damaging the lattice structure.

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