1. K. Takechi and M. A. Lieberman
Photoresist Etching with Oxygen Plasma in Large Area Plasma Source (LAPS)
SFR Workshop
November 8, 2000
K. Takechi and M. A. Lieberman
Berkeley, CA
2001 GOAL: Etch photoresist in the LAPS to examine process uniformity by 9/30/2001.
11/8/00

2. Experimental LAPS Setup
Antenna coil embedded in the plasma
Eight quartz tubes threaded by copper
antenna tubes
36.0 cm x 46.5 cm processing area
Plasma
Voltage sensor Rs
Xm(0.5uH) D X1
900 pF
(fixed)
12-
1000 pF
New series-parallel
system configuration
Vrf C
Bm1 B
Bm2
12-
500 pF X2 A
11/8/00

3. Oxygen Discharge Model
Substrate holder metal
(Center of the chamber)
(cm) 5
Side
metal
Calculation area
B.C.
Vn=0 r1 r2
….. r8 -5
-15 R
Quartz
15 (cm)
Chamber geometry used in the model
Particle balance :
Power balance :
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4. Ion flux profiles at substrate surface for various
gas pressures (simulation results)
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5. O-atom flux profiles lost to substrate surface for
various gas pressures (simulation results)
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6. Photoresist Etch Model
E.R. : Etch rate
ji : Ion current density at substrate surface
pO : O-atom pressure at substrate surface
kref : Ion-induced desorption rate constant at
Vbias= 0 V
Plots of etch rate vs.
pressure for various rf
powers. The fits are from
the above equation
with simulation results.
11/8/00

7. Effect of applying a substrate bias on etch rate and uniformity
Applying a Vbias leads to
increase in both etch rate
and uniformity over the
processing area.
Etch rate profiles at a gas pressure of 5 mTorr
at Vbias= 0 V and Vbias= -80 V
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8. Predicted etch rate profiles at a gas pressure
of 5 mTorr at k(Vbias)/kref=1 and k(-80V)/kref=4
Simulation results support
the experimental data, with
increase in the etch rate and
uniformity with applying
a bias.
11/8/00

9. 2002 and 2003 Goals
Modeling silane deposition processes in LAPS, by 9/30/2002.
Modeling reduced electron temperature and density processing plasmas in LAPS, by 9/30/2003.
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