🚀 go-pugleaf

Hi,
I'm working at measuring the roughness (Rq, Ra) of a thin oxide film
(500 Ang)over silion. I'm using a Wyko interferometer (NT3300) in
Phase Shift mode (PSI). I have results: Rq around 3-5Ang but I'm
questionning them... Hopefully it's not a stupid question??? Sorry if
it is I'm not an expert...yet...

Since the oxide is very thin (500 Ang)... is it really the bond oxide
roughness I'm measuring or I am seeing the silicon roughness due to
the transparency of the film??? If it would have been a very thick
oxide I would have been able to discriminate between the two set of
fringes... But it's so thin!!!!

I don't know if it makes any difference but i'm using the PSI filters
when I make these measurements.. (orange 565-645 nm or red light
640-660nm).

any thoughts????
If it does not work like this... is there something I can do with the
NT3300 so I can have the roughness of this bond oxide... (I know an
AFM would do the job, but it's not really an option for us)...

thanks

Karel Cote