Attached are 6 pictures of the same 4 inch wafer which was inside HAM2 for approximately 6 weeks.  These pictures were taken with either a Nikon D300 (DSLR with a NIKON F1.8 35mm lens) or a Nikon S8200 (point and shoot).  The wafer illumination was accomplished with either a FSI plug-in bar light or an LED flashlight.  The illumination was always from the side.  The cleanroom lights were also varied from on to mostly off.

The goal is to find a lighting method and camera system which can be used by all parties to document the accumulation of dust particles on the 4" wafers.  The method needs to be one which can be applied in-chamber without undue difficulty.

The method of illumination makes the largest difference in the ability to see particles.  The bar light clearly outperforms the flashlight.  Calum ordered two different models of inexpensive handheld LED bar lights which will be tried next.  Cordless, handheld lighting is the by far the easiest to deal with in-chamber.  The room lighting (dark preferred) also made a difference but not nearly as great as the direct lighting.  All pictures were handheld (no tripod) because a tripod is not practical inside a chamber.

There are some regions of high concentrations of small particles.  These are glove prints from moving the wafer around inside the chamber.  In one way, they disturb the sample, but in another way they also represent the actual surfaces inside of a chamber.

The next tests will use the cordless LED bar lights.  The F-stop of the D300 will be increased to increase the depth of field.

While we don't have a direct comparison of the amount of dust on the wafer before being hand-carried by Betsy to CIT, the test also shows that a significant amount of dust remained on the wafer during transport.  

Of course, the amount of dust found on this sample represents the amount of dust which can be expected to be found on all horizontal surfaces in HAM2.  

Participants: Betsy, Margot, Kate, and Jeff