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Disclosed is a method to measure ultra-low levels of alpha particles from powders without contaminating the counter. The method uses wafer semiconductor dicing tape to contain the particles.
English (United States)
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Measuring Ultra -
-Low Levels of Alpha Particles from Powders without Contaminating
Low Levels of Alpha Particles from Powders without Contaminating the Counter
Ultra-low alpha (ULA) particle emissivity (< 2 a/khr-cm2) materials are needed and used in semiconductor manufacturing to mitigate Single Event Upsets (SEU) in logic and memory devices. Powders are used in many semiconductor processes (e.g., plating); however, no effective method is in place to measure the associated alpha particle emissivity reliably at the ULA levels. Any loose powder can contaminate the counter. Exceptional care is needed because all counters (either gas proportional or ionization) have gas flowing, so the powder must be bound to a substrate . Additionally, to make the ULA measurement of the powder, it must be spread over a large (and flat) area.
An existing method includes a counter tray into which the powder is poured and then spread. Double-sided adhesive tape is applied to the rim of the tray and thin Mylar is stretched onto the tape to contain the powder . There are many problems with this approach.
The powder can be mixed into a ULA resin or epoxy. The drawback to this approach is that powder can settle so that the alpha particle measurements reflect the top layer of the resin, but not the powder.
The novel contribution is a method to measure ultra -low levels of alpha particles from powders without contaminating the counter.
To implement the method in a preferred embodiment :