How Do Particle Concentration and Face Velocity Impact the Removal of Sub-100-nm Particles from High-Purity Water?
By Grant, Beuscher & van Schooneveld
The critical feature size of state-of-the-art semiconductor devices line widths is < 20 nanometers (nm) and it is expected to decrease to < 10 nm by 2017 (1). Particles approximately half this feature size in the ultrapure water (UPW*) used during device manufacturing can reduce manufacturing yield and finished device reliability. Concentrations of these small particles in present day UPW systems are believed to be < 1E6/milliliters (mL) for particles >20 nm.
Microfiltration (MF) and ultrafiltration (UF) devices with particle removal ratings below 50 nm are commonly used to reduce particle concentrations in process water used during device manufacturing. The particle retention capability of these devices is frequently measured with challenge concentrations that are significantly higher (orders of magnitude higher) than those in UPW. Also, testing is often performed using filter face velocities that are very different from those used in UPW systems.
This article shows a number of examples which indicate that:
- Particle challenge concentration and face velocity can have a significant effect on particle retention.
- Filter particle retention measured under conditions other than expected operating conditions can be misleading.
- Test conditions used to measure filter retention should mimic actual use conditions as closely as possible in order to accurately predict filter retention characteristics in actual use conditions.
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