Optics are not keeping up with the pace of laser advancements. The laser industry is rapidly increasing its
power capabilities and reducing wavelengths which have exposed the optics as a weak link in lifetime failures
for these advanced systems. Nanometer sized surface defects (scratches, pits, bumps and residual particles)
on the surface of optics are a significant limiting factor to high end performance. Angstrom level smoothing
of materials such as calcium fluoride, spinel, magnesium fluoride, zinc sulfide, LBO and others presents a
unique challenge for traditional polishing techniques. Exogenesis Corporation, using its new and proprietary
Accelerated Neutral Atom Beam (ANAB) technology, is able to remove nano-scale surface damage and
particle contamination leaving many material surfaces with roughness typically around one Angstrom. This
surface defect mitigation via ANAB processing can be shown to increase performance properties of high
intensity optical materials. This paper describes the ANAB technology and summarizes smoothing results for
calcium fluoride laser windows. It further correlates laser damage threshold improvements with the
smoothing produced by ANAB surface treatment. All ANAB processing was performed at Exogenesis
Corporation using an nAccel100TM Accelerated Particle Beam processing tool. All surface measurement data
for the paper was produced via AFM analysis on a Park Model XE70 AFM, and all laser damage testing was
performed at Spica Technologies, Inc.
Exogenesis Corporation’s ANAB processing technology is a new and unique surface modification technique
that has demonstrated to be highly effective at correcting nano-scale surface defects. ANAB is a non-contact
vacuum process comprised of an intense beam of accelerated, electrically neutral gas atoms with average
energies of a few tens of electron volts. The ANAB process does not apply mechanical forces associated with
traditional polishing techniques. ANAB efficiently removes surface contaminants, nano-scale scratches,
bumps, particles and other asperities under low energy physical sputtering conditions. ANAB may be used to
remove a precisely controlled, uniform thickness of material without any increase of surface roughness,
regardless of the total amount of material removed. The ANAB process does not involve the use of slurries
or other abrasive polishing compounds and therefore does not require any post process cleaning. ANAB can
be integrated as an in-situ surface preparation method for other process steps in the uninterrupted fabrication
of optical devices.
Surface damage and surface contamination of optics has long been a source of problems for laser,
lithography and other industries. Nano-sized surface defects may present significant performance
issues in optical materials for deep UV and EUV applications. The effects of nanometer sized
surface damage (scratches, pits, and organics) on the surface of optics made of traditional materials
and new more exotic materials is a limiting factor to high end performance. Angstrom level
smoothing of materials such as calcium fluoride, spinel, zinc sulfide, BK7 and others presents a
unique set of challenges. Exogenesis Corporation, using its proprietary Accelerated Neutral Atom
Beam (ANAB) technology, is able to remove nano-scale surface damage and contamination and
leaves many material surfaces with roughness typically around one angstrom. This process
technology has been demonstrated on nonlinear crystals, and various other high-end optical
materials. This paper describes the ANAB technology and summarizes smoothing results for
various materials that have been processed with ANAB. All surface measurement data for the paper
was produced via AFM analysis.
Exogenesis Corporation’s ANAB processing technology is a new and unique surface modification
technique that has demonstrated to be highly effective at correcting nano-scale surface defects.
ANAB is a non-contact vacuum process comprised of an intense beam of accelerated, electrically
neutral gas atoms with average energies of a few tens of electron volts. The ANAB process does not
apply normal forces associated with traditional polishing techniques. ANAB efficiently removes
surface contaminants, nano-scale scratches, bumps and other asperities under low energy physical
sputtering conditions as the removal action proceeds. ANAB may be used to remove a precisely
controlled, uniform thickness of material without any increase of surface roughness, regardless of
the total amount of material removed. The ANAB process does not involve the use of slurries or
other polishing compounds and therefore does not require any post process cleaning. ANAB can be
integrated as an in-situ surface preparation method for other process steps in the uninterrupted
fabrication of optical devices.
EUV mask blank substrates will be subject to extraordinarily demanding requirements upon flatness, smoothness and
absence of residual defects. To date, no combination of available surface preparation techniques has been able to
produce essentially perfect substrates with zero residual defect populations. A critical problem yet to be resolved
involves small numbers of nanoscale divots and scratches which are generated by the operations used to meet
smoothness requirements. A new non-contact surface sputtering technique known as accelerated neutral atom beam
(ANAB) shows promise for mitigating the divot and scratch defects without increasing surface roughness and without
altering flatness and planarity. This paper describes a mask blank substrate study which has been conducted to
demonstrate the ANAB defect mitigation capability.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.