Thin bond oxide roughness measurement with optical profiler.

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2 total messages Started by Karel Cote Sat, 17 Apr 2004 01:25

#989

Author: Karel Cote
Date: Sat, 17 Apr 2004 01:25

26 lines
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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

Re: Thin bond oxide roughness measurement with optical profiler.

#990

Author: Calum Dickinson
Date: Sun, 18 Apr 2004 17:01

38 lines
2374 bytes

On 17 Apr 2004, Karel Cote wrote:

> 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).
> 
> 

Trying to view 50nm with a wavelength of an order of magnitude larger will
not give the resolution that you require. The use of an electron
microscope would be very useful, like was suggested by the other reply.
The microscope that i use , JEM 2011 TEM, the electron wavelength would be
0.00251nm which will give you a better resolution of the rough surface.
It's a possibility to use the SEM.

To use the anaolgy of my supervisor, Dr Wuzong Zhou, if you put a pebble
in a river then it is hard to see the ripples. put the same pebble in a
stream, then the ripples are easier to see. This is due to the river,
light, having bigger waves,wavelength, than a stream, electron,. I like
the analogy.

Calum Dickinson

************************
Calum Dickinson BSc Hons
Electron Microscopy Department
School of Chemistry
University of St Andrews
Scotland, UK

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