^{}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 10^{6}

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

J_{
0
}

Resist sensitivity

25 mJ/cm^{2}

A_{
f
}

Area of image field

1.3 cm^{2}

A_{wafer}

Total area to be exposed per wafer

288 cm^{2}

L

Optical path length near pupil plane

30 cm

D_{pp}

Diameter of pupil plane

15 cm

T_{pw}

Pupil plane to wafer transmission

78%

T_{mask}

Net mask transmission (ratio clear to chrome)

60%

U_{eff}

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 10^{6}

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.