Re: SRP with salicide on top

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Posted by Dan ( on July 19, 2011 at 15:44:27:

In Reply to: SRP with salicide on top posted by Luca Latessa on July 19, 2011 at 05:33:36:

: Hi, I would need to get SRP of high dose S/D implants (As and B) after a Ge implant amorphization and cobalt salicide formation on the wafer surface.

: My question is if the SRP measurement is possible with that low resistivity salicide film (~200A) on top, or if it is necessary/advisable that I strip it away prior to the measurement.

Thank you for your excellent question. Yes SRP measurements are affected by surface salicides. The very low resistivity of the salicide creates a low resistance pathway that the SR measurement will use while in proximity. This creates an artificially low spike in the surface resistivity. Once the probes are their probe spacing away from the silicide they recover the appropriate resistance. Since the probes are usually run with 25um spacing this means any measurements within the first 12um of the bevel edge could be affected. If the profile is run with a 2um step, this means 6 data points may be suspect.

So. Does this mean you should remove the silicide films? Some say yes because they want to see the true surface concentration while others say no because they can't remove the silicide without removing the sintered silicon as well which makes their thicknesses different. It will be up to you to decide which is more important to your experiment. If you leave the silicide on the sample we usually include it in your depth profile plotted as "S" characters. They will be plotted at carrier concentration or resistivity values but those values will be wrong as we do not have any reference samples to correct the measurements to. The only reliable value associated with the S layer is the thickness.

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