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continues to decline as resolution increases, would still be within a
reasonable manufacturing DOF budget with glass substrates.
As with CCL, ABF, RDL and via processing would all need to
be modified to meet 2/2µm l/s requirements. Some of the process
steps described previously would be similar, but below 2/2µm
l/s additional processes would need to be employed, especially
for copper RDL plating seed removal. This particular process is
isotropic and subjects the entire panel to a brief flash etch, which
not only removes the seed material, but also the RDL metal,
thereby reducing line width and impacting critical dimension (CD)
uniformity. To resolve this issue, damascene processing has been
proposed; this would require lithography to pattern RDL trenches
in the ABF or PID and chemical mechanical planarization (CMP)
Figure 2: Glass substrate. to remove the excess copper to generate copper RDL interconnects.
substrates instead. For instance, overlay of the via to RDL would be Lithography system solutions
significantly improved as the glass would maintain its dimensions Currently, AICS CCL manufacturers are using extremely
and not suffer from distortions by curing organic dielectric large field steppers (250mm x 250mm) with substrate formats of
materials. The glass substrate would support higher resolution 510mm x 515mm and 600mm x 600mm. However, there is some
lithography. As such, the depth of focus budget would not be lost discussion of 650mm x 650mm substrates, but these are not
to substrate non-flatness. This would allow lithography tools to mainstream. These extremely large field steppers achieve high
increase their numerical aperture (NA) to achieve the highly sought throughputs in excess of 110 panels per hour (PPH).
after 2/2µm l/s but sacrificing depth of focus (DOF) in the process, In addition to steppers, printed circuit board (PCB)
as described by Rayleigh’s criterion. The reduced DOF, which manufacturers are experienced with laser direct imaging (LDI)

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