High Throughput Laser Drilling for 3D IC TSV

There will be a major presentation
by XSil at the upcoming IMAPS Device Packaging meeting in Phoenix
in March. In keeping with Semiconductor Internationals goal of
getting you all the leading edge 3D information as soon as possible
in this Perspectives from the Leading Edge blog,
I”ll give you a taste of what to expect in the following
paragraphs.

Without question the author /
presenter Alexey Rodin is one of the world experts in using lasers
for 3D TSV processing. We have previously noted that Alexey and
XSil were making some significant advances in laser processing with
vias down to 10 microns now possible (Perspectives From the
Leading Edge - “Going Verticle in Whitefish” - Sept 9th 2007).
Being maskless, the laser process obviously eliminates PR coat,
expose, develop and strip processing The laser process also
naturally produces sloped sidewalls which are much more conducive
to barrier and seed layer deposition. In addition by controlling
the laser pulses one is able to “drill” through oxide
and nitride layers as well as Al, Cu, Ni and Ti metallizations.
Initial announcements from memory manufacturers like Samsung have
indicated that they are looking long and hard at such laser
processing.

This March Alexey will show results
from the X300V Ultra production tool showing that the laser
drilling process is insensitive to via position on the wafer and
via depth uniformity across a 300 mm wafer is currently +/- 4% and
they are implementing controls so that this approaches +/- 1% in
the future. It will be reported that Si removal rates exceeding 20
um per laser pulse are now possible.

For example this translates into 17K
vias per minute for a 300 mm wafer with 657 die with 100 (20 um dia
x 60 um deep ) vias per die ( i.e 15 wafers per hour)
…or…53k vias ( 15 um dia x 50 um deep) vias per
minute for a 300 mm wafer with 1000 vias per die (4-5 wafers per
hour).

R&D is currently going on for
vias in the 4-6 um diameter range for DRAM and logic applications.
So far they have been able to achieve excellent results by proper
opto-mechanical tool design.

For more dertail on these very
exciting results attend Alexeys session in the IMAPS Device
Packaging meeting. For more of the latest information on 3D IC
integration stayed linked to Perspectives from the Leading
Edge……………….