Abstract:

The primary industry driving the reduction of particles in ultrapure water (UPW) systems is the semiconductor industry. Particles that can produce defects in chip manufacturing and potentially reduce yield are now identified to be 10 nm and smaller. Isolating and collecting particles in this size range using the classical filtration technique of sieving is limited, time consuming and in many cases, ineffective. Searching for 10 nm particles on a 25 mm filter with a total surface area of more than 500 mm2 (500,000,000 nm2) is quite laborious.

Focused Aerosol Deposition (FAD) is a technique that combines extraction of nanoparticles from UPW via nebulization with focused droplet deposition on a SEM-ready stub providing an extremely localized collection of particles as small as 5 nm. Improvements in aerosol focusing, evaporation management and direct deposition on SEM-ready media has resulted in a focal point as small as 0.005 mm2 with repeatable positioning. By maintaining a tight collection area, the time required to collect sufficient particles for analysis is reduced 50 to 90% compared to traditional filtration methods and provides improved sizing analysis via SEM and elemental analysis using Energy Dispersive X-ray Spectroscopy (EDS).

This paper will review the enabling technologies associated with FAD, provide SEM/EDS analysis of collected UPW samples and discuss potential of the technology for particle characterization and identification, and risk mitigation in UPW systems.