Re: About SRA

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Posted by Dan ( on February 09, 2011 at 16:13:04:

In Reply to: About SRA posted by William Lai on February 09, 2011 at 01:10:18:

: How do Solecon Lab. confirm starting point is at top surface?

The SR probes leave marks on the sample every time they take a measurement. We call these marks the "footprints." After a scan is run the technician looks at the marks left on the sample and can count how many were on the surface and where the bevel edge crosses the scan. It is either under a set of footprints or between two sets. This information is recorded and is used to process the data.

I should probably mention our understanding of "top surface." We call the bevel edge of bare samples the top surface. If there are oxides or other coatings we use the interface of these coating and the silicon (or germanium or other materials) as the bevel edge. In the case of poly or other films of interest that may be on the substrate or oxide films, we will use their top surface as the bevel edge. We can also include silicide films and often do because the silicide has a major influence on the first few points measured on the bevel past the silicide interface due to it's extremely low resistivity. If poly is directly on the substrate we can usually see fringing in the poly and will make a note of it. But we won't exclude the poly from the profile unless there is an oxide between it and the underlying substrate.

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