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Wet cleaning for polymer removal has
become more challenging with the continuous
increases in density and number
of interconnects and shrinkage of feature
sizes in the semiconductor industry.
Amine-based chemistries such as EKC
are the most commonly utilized solution
for removal of post etch residues from
vias, contacts and metal lines[1-6].
Cleaning solutions are introduced into the
cleaning chamber using spray nozzles
on the side of the chamber. The Semitool
SST batch solvent processing tool
removes etch polymer residues commonly
left behind at the sidewall and
bottom of the contacts (or vias) and on
the surfaces of the metal lines and the
spaces between them. Good via cleaning
is important to avoid via glue layer
coverage issues that can result in open
via issues. Good metal line cleaning is
important to avoid shorts between the
lines and reliability failures. In the development of 90 nm technologies,
we attempted to improve BEOL
cleans by using the enhanced spray
technology (EST) upgrade on the
Semitool SST batch tool. The SST is a
self-contained, batch spray processor
capable of cleaning wafer load sizes up to
100 wafers. Chemical is delivered from
multiple spray manifold positions located
in the process chamber, providing
uniform spray distribution on all wafer
surfaces. The EST upgrade utilizes more
spray nozzles at higher spray velocities
to improve the spray pattern onto the
wafer surface. The EST upgrade involves a
new bowl design as shown in Figure 1.
There are two rows of nozzles per
manifold compared with one row in the previous design. The rinse manifold uses
0.2 gal/min nozzles, while the chemical
manifold uses 0.1 gal/min nozzles. This
compares to the previous standard
configuration of 0.8 gal/min nozzles on
both manifolds. Also included in the
upgrade is a chemical and water supply
valve sizing increase that boosts flow
volume available to the manifold –
contributing to a more uniform and
vigorous spray pattern. These upgrades
result in major improvements in our
solvent post etch cleans performance.
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