F2 cleans faster than SF6: 4x cleaning
rate improvement
F2 cleaning requires 75% less gas by
mass
F2 activation uses 50% less rf power
at higher cleaning rates vs BKM for SF6
Figure 3. rf Plasman cleaning on an Oerlikon tool: F2 vs SF6
SUMMARY
Performed on AKT 15k tool,
1200x1300mm2
a-Si thin films 200 C
F2 cleans faster than NF3: 2.7x extendable to 4x with higher flows
F2 requires 20% less gas by mass
F2 activation uses 50% less electrical
power
Figure 4. RPS plasma cleaning on an AKT /
AMAT tool: F2 vs NF3
F---F
F2
159
Bond Energies [kJ/mol]
NF3
248
278
316
F2N---F
FN---F
N---F
F5S---F
F4S---F
SF6
of cleaning gas activation need to be considered to understand and exploit the significant
process advantages available when using F2
versus other F-gas alternatives. After a short
look at this fundamental science, we present
process data from a variety of tools and applications that demonstrate these advantages.
➞ F. from F2: 80 kJ/mol
➞ F. from NF3: 281 kJ/mol
➞ F. from SF6: 308kJ/mol
Table 1. Bond strengths of CVD chamber cleaning gases
Table 2. Activation energy for CVD chamber cleaning gases
between molecular F2 and the silicon thin
films used in photovoltaic cells has been
demonstrated as a very fast alternative
method for this application.
Both the thermodynamics, or chemical
energy, and kinetics, or chemical pathways,
The Chemistry of Fluorine
As the most electronegative atom in the
periodic table, fluorine forms strong bonds
with most other atoms, including some
stable compounds with rare gases. It’s not
surprising then that CxFy and NF3 both have
very high bond energies—the amount of
energy required to release fluorine radicals.
In contrast, fluorine forms a very weak bond
