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Unlike traditional filtration, the objective of a slurry filter is for the majority of particles to pass through it unchanged, while only removing the undesired or "oversized" particles. These oversized particles are 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 particle counts can also occur due to shipping conditions, shearing, slurry drying, and interaction with other components in the distribution loop like fittings, valves, pumps, and piping. These large particles can scratch inter-level dielectrics and metal layers potentially causing wafer defects.
It is important to recognize that slurries vary greatly from one manufacturer to another, and therefore a customized solution is required. Several factors are important in selecting the appropriate slurry filter of which particle classification, retention efficiency, flow rate, differential pressure, contaminant holding capacity, and filter lifetime are some of the most important.
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