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of the second layer included site-by-site
correction for each exposure field. Overlay
error was checked by reading overlapped
verniers (Figure 9) included at certain
locations in the patterns. Each exposure
field contains 3 x 3 measurement points;
and 2 x 2 shots per panel were measured
to determine the overlay performance. The
mean +3 sigma in X was 0.91µm, and the
mean +3 sigma in Y was 0.91µm. The table
in Figure 9 summarizes the results of the
overlay error measurements.
Summary
In this study, an extremely large
exposure field size (250mm x 250mm)
successfully resolved 3µm line/space
features with a depth of focus >60µm on
a 510mm x 515mm CCL/ABF stack with
a 10µm-thick dry film resist. This study
also demonstrated successful 5µm and
6µm line/space features with a 25µm-thick
dry film resist and 15µm and 20µm vias
with a 40µm-thick dry film resist. Fine
resolution and a large field size provide
the user with the opportunity to increase
the package size beyond 150mm x 150mm
and maintain high throughput. This new
capability has the potential to pave the way
Figure 7: a) Bossung plot for 15μm vias showing 110μm DOF. b) Bossung plot for 20μm vias showing 110μm DOF.
Figure 8: a) 3µm CD plot in 250mm x 250mm exposure field: The maximum CD is 3.258µm, and the minimum CD is 2.988µm; the average CD is 3.099µm, and the
uniformity is 4.32%. b) 3µm CD deviation contribution map in 250mm x 250mm exposure field: The center location has a minimum deviation of -0.20% and the deviation
trend up to 2.2% to 4.12% at corner locations, the maximum deviation is 4.12%, which is at the top-right corner. Overall, the deviation meets our expectation. c) 3µm CD
and CD deviation chart: No trending or peak is observed. This chart indicates the CD performance with a 250mm x 250mm exposure field is stable.
Figure 9: A summary of the results of overlay measurements: a) Overlapped verniers included in the pattern were used to measure overlay errors. b) The table
summarizes the measured errors.
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