R. Schenker is with Intel Corporation, Santa Clara, California 95052. USA
W. Oldham is with the Electronics Research Laboratory and Department of Electrical Engineering, University of California, Berkeley, California 94720. USA
Richard Schenker and William Oldham, "Damage-limited lifetime of 193-nm lithography tools as a function of system variables," Appl. Opt. 37, 733-738 (1998)
Model diffraction-limited optical systems are examined for the
effects of radiation-induced compaction on optical performance. The
Zernike phase aberration terms resulting from 193-nm-induced compaction
in a model lithographic system are calculated with Fourier optics and
ray tracing. Using experimental densification rates and the
extracted aberration terms, we develop equations describing a useful
system lifetime as a function of relevant system variables. In the
example examined, the useful life depends strongly on the throughput,
resist sensitivity, and partial coherence.
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Throughput in 200-mm wafers per hour (wph) [defined by Eq. (2)]
65
κ
Fused-silica compaction coefficient [defined by Eq. (1)]
0.2 parts in 106
Table 2
OPD per Centimeter of Fused Silica at 193 nm for
(Δρ/ρ)u = 1 ppm for Different Lens
Geometriesa
Illumination Diameter
Sample Length (cm)
0.5
1
2
2 cm
0.011λ
0.012λ
0.012λ
5 cm
0.013λ
0.013λ
0.013λ
8 cm
0.016λ
0.016λ
0.016λ
Calculated with finite element analysis
and Eq. (3).
Table 3
Induced Wave-Front Aberrations in Waves (λ = 193 nm)
from 1-ppm Unconstrained Compaction in Elements near the Pupil Plane
for Single-Beam Pass (30-cm Total Path Length)
Induced Wave-Front
Aberrationsa
in Waves (λ = 193
nm) from 1-ppm Unconstrained Compaction (in Single-Pass Intensity
Regions) in Elements near the Pupil Plane with Folded Beam Path
Calculated for system damage scaled to
1-ppm unconstrained peak compaction in the center of the 6 cm of
optical path in the model system near the wafer plane.
Maximum unconstrained compaction in system
equal approximately 10 ppm.
Defined in text.
Tables (5)
Table 1
Definition of Symbols Used in Analysis
Symbol
Definition
Example Value
τ
193-nm laser pulse length
11 ns
J0
Resist sensitivity
25 mJ/cm2
Af
Area of image field
1.3 cm2
Awafer
Total area to be exposed per wafer
288 cm2
L
Optical path length near pupil plane
30 cm
Dpp
Diameter of pupil plane
15 cm
Tpw
Pupil plane to wafer transmission
78%
Tmask
Net mask transmission (ratio clear to chrome)
60%
Ueff
Usage efficiency of system (fraction of time laser energy passes through system optics)
Throughput in 200-mm wafers per hour (wph) [defined by Eq. (2)]
65
κ
Fused-silica compaction coefficient [defined by Eq. (1)]
0.2 parts in 106
Table 2
OPD per Centimeter of Fused Silica at 193 nm for
(Δρ/ρ)u = 1 ppm for Different Lens
Geometriesa
Illumination Diameter
Sample Length (cm)
0.5
1
2
2 cm
0.011λ
0.012λ
0.012λ
5 cm
0.013λ
0.013λ
0.013λ
8 cm
0.016λ
0.016λ
0.016λ
Calculated with finite element analysis
and Eq. (3).
Table 3
Induced Wave-Front Aberrations in Waves (λ = 193 nm)
from 1-ppm Unconstrained Compaction in Elements near the Pupil Plane
for Single-Beam Pass (30-cm Total Path Length)
Induced Wave-Front
Aberrationsa
in Waves (λ = 193
nm) from 1-ppm Unconstrained Compaction (in Single-Pass Intensity
Regions) in Elements near the Pupil Plane with Folded Beam Path
Calculated for system damage scaled to
1-ppm unconstrained peak compaction in the center of the 6 cm of
optical path in the model system near the wafer plane.
Maximum unconstrained compaction in system
equal approximately 10 ppm.
Defined in text.
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