Particle contaminants in semiconductor process fluids, such as ultrapure water (UPW) and air, is the bane of the industry and the cause of many defects on wafer surfaces. With ever shrinking wafer nodes, the size of a killer particle is now as small as 7 nm. Traditional on-line monitors, called laser particle counters, reached their theoretical detection limit at 20nm. Without methods to monitor fluid purity at the node size, yield-reducing particle contaminants can exist without warning. Process engineers have little information to go on to identify the source of the problem.
Focused Aerosol Deposition
Our high-efficiency nano-particle sampler, Nano SpotLight™, collects a focused 1-mm “spot” deposit of particles as small as 5 nm on a dry substrate such as a test silica wafer. The sample is analyzed off-line using powerful scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDX). The analysis characterizes the quantity, size, shape and chemical composition of the particles. Visualizing the particles and knowing their chemical makeup allows the process engineer to rapidly identify the contaminant source and take corrective action. The sampling can be done in less than 24 hours, sometimes in just a few minutes if there is a high contamination excursion.
The Nano SpotLight can be used to collect contaminant particles in air or in UPW. To aerosolize the particles from a water source, the UPW is first nebulized using a high-purity NanoParticle Nebulizer (Kanomax Inc.).
The alternative method of collecting particles for off-line analysis uses membrane filtration. It takes up to three weeks to collect a sample. Particles are dispersed throughout the entire 25-mm filter surface and are difficult to locate under the microscope. Even worse, the membrane filters are inefficient at collecting particles smaller than the filter’s 50-nm pore size which happens to be the particles of greatest interest.
For more information, contact:
Pat Keady, President, info (at) aerosoldevice.com
Nano SpotLight references:
David Blackford, D. Ph.D., D. Oberreit Ph.D., S. He Ph.D., G. Van Schooneveld, C. Howe, P. Keady, V. (Slava) Libman Ph.D. A New Method for the Rapid Identification of sub-20nm Particles in UPW. UPW Micro 2017, Portland, OR, May 30, 2017.
UPW 2017-Spot Sampler NPN Abstract.
UPW Power Point Presentation
Van Schooneveld, G., S. He, P. Keady (2017) A comparison of optical particle counting and aerosol-based particle counting technologies for UPW monitoring and diagnostics, Ultrapure Water Micro 2017, Portland, Oregon,May 30. Presentation pdf