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Total
Metal Loss
Parameter
of Choice
for Evaluation of Metal CMP Processes |
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The
major process and consumable development challenge in Metal CMP is
reducing the amount of dishing and erosion, which are two key pattern
and time dependent variations. These effects are shown in the figure
below. |
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Dishing
is usually assocated with the metal loss in a single metal line, and
erosion is usually assocated with the oxide loss in an array of lines. |
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Note
: There is no consistent definition of dishing and erosion in industry.
Some literature may refer dishing as metal recess and refer to erosion
as some combination of oxide thinning in ther field region plus structure
erosion (now defined as the step difference between the polished oxide
thickness and a structure region). |
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Up
to now, most researchers and development engineers in metal CMP
have measured the dishing and erosion using profilometry surface
scans without the determination of the field oxide loss shown in
the figure.
We
believe the dishing and erosion values alone do not give proper
guideline for the evaluation of metal CMP processes.
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The
better metric which can give us the true measure of metal CMP is :
total metal loss (which is a sum of field oxide loss and
dishing and erosion values). |
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Total
Metal Loss = (CMP Field Oxide Loss) + (Erosion) + (Metal Array
Dishing)
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Our
current recommended metrology consists of profilometry surface scans
combined with oxide thickness to understand the amount of total
metal loss.
Pre-and Post-CMP optical oxide thickness measurements are required
to relate the surface profile scans to total metal loss.
Our
new SKW5-3 W and SKW6-3
Cu CMP process characterization wafers are designed for CMP engineers
to determine the total metal loss accurately after the CMP experiment.
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SKW
Associates, Inc.
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