Use of a commercial RF Plasma Cleaner in eliminating

1
Use of a commercial RF Plasma Cleaner in
eliminating advenitious carbon contamination in
an XPS system
background
Liz Strein, David Allred, department of physics
and astronomy
When studying the removal of a thin layer of
adventitious carbon it is critical to ensure that
the instruments used to characterize the surface
are not contributing to the contamination We
found that the antechamber of the XPS system
deposited carbon onto clean and dirty samples,
making it impossible to use XPS as a way to
characterize surface cleanliness. Using the RF
Plasma Cleaner to clean the chamber virtually
eliminates contamination from the chamber. By
ensuring that the chamber was not a source of
contamination, XPS could be used as a
characterization technique. As a result, we were
able to study the effectiveness of various
cleaning treatments
image from http//sdo.gsfc.nasa.gov/images/site/po
pscise.jpg used with permission
Contaminations Effect
After
Before
J. Tveekrem, Contamination effects on EUV optics,
NASA Technical Report TP-1999-209264 (1999 Used
with permission
XPS Antechamber a source of contamination without
the aid of a RF Plasma Cleaner
Methodology
Acknowledgments Ron Vane and Gabe Morgan for
their excellent product, the EVACTRON C RF
Decontamination System Dr. R. Steven Turley ,
Dr. Matt Linford, and Lei Pei College of
Physical and Mathematical Sciences for funding
Previous to their exposure to the XPS system,
these samples were cleaned using atomic oxygen in
air, by placing the samples within 1 cm of an
excimer lamp in air for at least 5 min. The
oxidation process frees the SiO2 of adventitious
carbon (AC). Use of spectroscopic ellipsometry
(SE) provides a method of characterizing surface
cleanliness. With the use of the lamp, the
apparent thickness of the oxide layer (really a
layer of oxide and AC) would decrease to 1.8 nm,
the thickness of the native oxide. When we
introduced the clean samples to the XPS
antechamber, we saw an increase in the apparent
oxide thickness and XPS scans showed a large
carbon presence. However, after we installed
Evactron-C plasma decontamination system,
adventitious carbon was virtually eliminated