Dear Yao,

Recent replies on the topic were all correct. The refractive index of a
typical LPCVD silicon oxide (SiOx) is around 1.46 +-0.01 (@633 nm). However,
I think that you should be careful with the growth parameters. More
precisely, the relative amounts of silicon and oxygen in your film may
deviate from ideal SiO2. If during the growth process the amount of supplied
oxygen is insufficient you can end-up with silicon rich oxide, which in turn
implies a film with a refractive index higher than 1.46. The highest
possible index in this case  is about ~2. In order to avoid this situation
you can use excess O supply during the growth (increase the precursor gas
flow rate supplying oxygen).

Regards,


Feridun Ay
Bilkent University
Ankara




-----Original Message-----
From: Qing Yao [mailto:qingyao@uiuc.edu]
Sent: 14 May 2004 19:46
To: MEMS-talk
Subject: [mems-talk] refraction index of LPCVD silicon dioxide

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