Plasma cleaning of nanoparticles from EUV mask materials by electrostatics

W. M. Lytle, R. Raju, H. Shin, C. Das, M. J. Neumann, D. N. Ruzic

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Particle contamination on surfaces used in extreme ultraviolet (EUV) mask blank deposition, mask fabrication, and patterned mask handling must be avoided since the contamination can create significant distortions and loss of reflectivity. Particles on the order of 10nm are problematic during MLM mirror fabrication, since the introduced defects disrupt the local Bragg planes. The most serious problem is the accumulation of particles on surfaces of patterned blanks during EUV light exposure, since > 25nm particles will be printed without an out-of-focus pellicle. Particle contaminants are also a problem with direct imprint processes since defects are printed every time. Plasma Assisted Cleaning by Electrostatics (PACE) works by utilizing a helicon plasma as well as a pulsed DC substrate bias to charge particle and repel them electrostatically from the surface. Removal of this nature is a dry cleaning method and removes contamination perpendicular from the surface instead of rolling or sweeping the particles off the surface, a benefit when cleaning patterned surfaces where contamination can be rolled or trapped between features. Also, an entire mask can be cleaned at once since the plasma can cover the entire surface, thus there is no need to focus in on an area to clean. Sophisticated particle contamination detection system utilizing high power laser called DEFCON is developed to analyze the particle removal after PACE cleaning process. PACE has shown greater than 90 % particle removal efficiencies for 30 to 220 nm PSL particles on ruthenium capped quartz. Removal results for silicon surfaces and quartz surfaces show similar removal efficiencies. Results of cleaning 80 nm PSL spheres from silicon substrates will be shown.

Original languageEnglish (US)
Title of host publicationMetrology, Inspection, and Process Control for Microlithography XXII
StatePublished - 2008
EventMetrology, Inspection, and Process Control for Microlithography XXII - San Jose, CA, United States
Duration: Feb 25 2008Feb 28 2008

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherMetrology, Inspection, and Process Control for Microlithography XXII
Country/TerritoryUnited States
CitySan Jose, CA


  • Contamination
  • EUVL mask cleaning
  • Electrostatics
  • Particle removal

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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