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Betapure™
CMP Series
CMP Filter Cartridges
Superior Reduction Of Large Particle
Counts For Improved Yields
Betapure™ CMP filter cartridges are high capacity depth filters optimized for oxide and metal
slurries used in chemical mechanical planarization (CMP) applications. Betapure CMP filters are
composed of all-polypropylene components and features a multi-zone "graded-porosity" design
for the optimum level of particle classification. This novel construction provides enhanced flow
characteristics, including low pressure drop, to minimize shearing of the slurry while providing
superior service life.
The objective of a slurry lter is for the majority of particles to pass through it unchanged,
while only removing the undesired or “oversized” particles. The oversized particle population
is commonly referred to as large particle counts (LPC) and they typically form over time when
the suspended particles in the slurry settle forming aggregates, agglomerates, and gels. Large
particles can also be the result of ad verse shipping conditions, shearing, slurry drying, and
interaction with other distribution loop components such as ttings, tanks, piping, valves, and
pumps. These large particles can scratch metal and inter-level dielectrics potentially causing
wafer defects. The Betapure CMP lter reduces large particle counts that can potentially
reduce yields while maintaining the polishing characteristics of the slurry.
Applications
Semiconductor Oxide/Low-k Dielectrics, Shallow Trench
Features & Benefits
Graded Porosity Design
Superior removal of hard and soft gel contaminants, for reduced defectivity
and improved yields
High contaminant holding capacity reduces downtime and increases overall
equipment effectiveness
The filters are "matched" to the slurry providing the optimum level of
performance needed to dramatically reduce defect causing particles
Provides a low pressure drop reducing the potential for fluid shear of the slurry
100% Polypropylene
Low cartridge extractables, free of adhesives, binders, and surfactants
Excellent chemical compatibility with low and high pH slurries
Quality Manufacturing
ISO certified quality management system
Non-contact welding reduces a potential source for contamination
Manufactured and double-bagged in a clean environment to provide superior downstream cleanliness out of the package
Built to Exacting Specifications
Provides a consistent quality of slurry enabling repeatability of the planarization process
Data Storage Magnetic Heads, Nickel and Glass
Data Transmission Optical Fiber
Compound Semiconductor Light Emitting Diodes (LED)
Isolation (STI), Inter-level Dielectric (ILD),
Polysilicon, Tungsten, and Copper
Substrates
1
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Particle Size Distribution
The filtration of CMP slurries is a unique and challenging process as compared to the filtration of high purity chemicals used in electronics
manufacturing. High purity chemical filtration is typically performed using 0.2 micron or tighter membrane filters that have a sharp particle
removal cut-off at the rated pore size. The majority of CMP slurries contain a de sired mean particle size that ranges from 0.03 - 0.2 microns.
Consequently, the filter that was specifically designed for particle clarification of high purity chemicals would strip out the de sired particles and
adversely affect the polishing characteristics of the CMP slurry. Over sized particles in the slurry typically greater than 0.5 micron are undesired
and represent the “tail” (Figure 1) of the particle size distribution (PSD). Betapure™ CMP filters remove the PSD tail while allowing the majority
of desired or “target” size particles to pass through it unchanged
.
Particle Removal Efficiency is the Best Measure of Filter Performance
Figure 1 com pares the PSD of colloidal-silica slurry and a lab oratory test dust which is typically used by filter suppliers to establish depth filter
ratings. The data shows that test dust has a broader PSD above 0.5 micron proving that it is not a true representation of the types of particles in
CMP slurry. A wide variation in performance also exists from one filter supplier to the next because there is no industry accepted standard for
rating retention of depth filters. Furthermore, Absolute and Nominal filter ratings are both used to specify particle removal efficiency which
only serves to confuse the situation while not providing the application specific information needed. In Figure 2, particle removal efficiency is
compared for the same grade of CMP filters from 3M Purification. The filters were challenged using both a lab oratory test dust and colloidal
silica slurry. There is a significant difference in particle removal efficiency, which is a direct result of the contaminant PSD distribution. The
broad PSD of the test dust yields significantly higher particle removal efficiency than achieved when tested with slurry. Therefore, test dust is not
representative of slurry and ratings based on test dust will likely be over stated and meaningless for CMP slurry applications. In Figure 3, particle
removal efficiency is compared for equivalent rated CMP filters from 3M Purification Inc., Competitor P, and Competitor M in colloidal silica
slurry. The data clearly shows that equivalent rated filters from different manufacturers does not deliver equivalent performance and reinforces
the fact that the “rating” generated in a lab using test dust is not meaningful in predicting actual performance. Based on this information particle
removal efficiency generated in slurry is the best measure of filter performance. Other important factors in selecting the appropriate slurry filter
include particle classification, pressure drop, and filter lifetime..
Number of Particles per ml
Figure 1. - Particle Size Distribution > 0.5 micron - Colloidal Silica Slurry & ISO Test Dust
200000
Colloidal Silica Slurry
150000
100000
ISO Test Dust
50000
0
0.5 1 2 105
Particle Diameter (microns)
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Betapure™ CMP Series
CMP Filter Cartridges
Particle Removal Efficiency
Colloidal Silica vs. ISO Test Dust
Betapure CMP560 - Colloidal Silica
Betapure CMP560 - ISO Test Dust
100
80
60
40
20
0
Particle Removal Efficiency (%)
Figure 2. - Particle Removal Efficiency Figure 3. - Comparative Particle Removal Efficiency in Colloidal Silica
Particle Size > 0.54 micron
Superior Particle Retention through
Graded Porosity Design
Betapure™ CMP filter media was specifically engineered to provide a low
porosity, downstream section with a sharp retention cut-off that closely aligns
to the size distribution of undesired particles to be removed. This sharp removal
cut-off will not alter per cent solids (Figure 4) or re move de sired or “target” size
particles thus preserving the polishing characteristics of the slurry. In contrast,
competitive point-of-use filters (Figure 4) that have a broad removal range can in
fact retain particles smaller than the PSD. Re moving these “target” size particles
can alter the per cent solids of the slurry which in turn reduces filter lifetime
because more particles are being re moved than required in the application.
The multiple higher porosity layers on the upstream section (Figure 5) provide
effective pre-filtration of over sized particles resulting in higher contaminant
removal capacity and increased filter life-time. This novel graded porosity
(Figure 5) design also provides a tortuous downstream path and low pressure
drop which is ideal for gel capture and reduced shear effect on the slurry.
Particle Removal Efficiency
for Equivalent Rated Filter Cartridges
Betapure CMP
Competitor P
Competitor M
100
80
60
40
20
0
Particle Removal Efficiency (%)
> 0.54 micron > 1.01 micron
Percent Solids - Colloidal Silica
Influent
Effluent
0.5
0.4
0.3
0.2
0.1
Percent Solids (%)
0
Competitor P Betapure CMP
Figure 4. - Percent Solids Comparison
TM
Superior Particle Retention through
Graded Porosity Design
Large particles, greater than 0.5 micron, can scratch metal and interlevel dielectrics
potentially causing wafer defects. Variations in particle size distribution and
particle counts in the slurry can affect re peat ability of the planarization process.
In both cases, major reductions in large particle counts can be associated to proper
filtration, resulting in reduced defectivity (Figure 6) and an increase to yields. Proper
filtration also provides a consistent quality of slurry which enables repeatability
of the planarization process. The ideal slurry filter will have a retention curve that
closely aligns to the PSD of “undesired” particles to be removed. By matching that
characteristic, Betapure CMP filters are able to maintain the polishing characteristics
of the slurry, maximize contaminant holding capacity, and increase filter lifetime.
3
Flow Direction
Inner
Outer
Medium
Figure 5. - Graded Porosity Design
Medium