Filters Particles Monitoring Analytics

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Abstract

The critical features size of state-of-the-art semiconductor devices is on the order of 50 nanometers (nm) and expected to decrease to approximately 20 nm by 2015 (1). Particles on the order of one-half the feature size in the high-purity water (UPW)* used during device manufacturing can reduce device manufacturing yield and finished device reliability. Microfilters and ultrafilters with particle removal ratings below 50 nm are often used to control particle concentrations in the process water used in device manufacturing. However, the ability of the filters to remove particles is typically measured using optical particle counters with a minimum detection limit of 50 nm or larger. This article describes a new technique that allows measurement of retention of particles as small as 10 nm in diameter. In this technique, filter cartridges are challenged with a polydispersed mixture of polystyrene latex (PSL) beads ranging from 10 to 100 nm in diameter. Total concentrations ranging from 3x108 per milliliter (/mL) to 1010/mL ﾳ 10 nm are used. Filter inlet and outlet concentrations are measured using ultrafine atomization, a recently developed measurement technique (2). In this technique, a very fine mist of particle-laden UPW is created, the water in the mist droplets is evaporated and the sizes and number concentrations of the remaining particles are measured using a scanning mobility particle sizer (SMPS). This technique allows very accurate measurement of particle size with 64 size channels between 10 and 100 nm.

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