Dear Yao,

1.7 to 2.0 is must too high. As Roger Shile states, the refractive index of
silicon oxide
(thermal grown at 630 nm) is around 1.46. However since LPCVD silicon oxide is
less dense
than thermal grown oxide, I would expect at slightly lower refractive index and
not a
higher index.
When you fit ellipsometer measurements with at model of your layer, start with a
fixed
index of 1.46, and change the film thickness until you get a reasonable good
fit. First
then you should fit the refractive index. As the oxide thickness increase, you
need at
better and better guess for the initial thickness. Otherwise the algorithm finds
at local
minimum and stay there.

regards,
Gert Eriksen







> I think it might be around 1.7-2.0
>
> -Mike
>
>
> >>> qingyao@uiuc.edu 5/14/2004 12:45:50 PM >>>
> Hi,
>
>
> I was wondering if some one could tell me the typical value of
> refraction
> index of LPCVD Silicon Dioxide. It is deposited at about 420 degrees
> centigrade on a silicon wafer. I use a focus ellipsometer to measure
> its
> thickness. I tried 1.46 but got very large fit error (about 500).
> Please let
> me know if you have any information about this. Thanks!
>
>
> Best Regards,
>
>
> Qing Yao
> ___________________
> M&IE @ UIUC
>
>
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