Hi Lungo-hao,

I guess it was due to "bubble" caused by mixing.
You can remove it by vacuum before spin-coating.
There is an another possibility that it was due to a lack of mixing.

Hope this would be helpful for you.

Thanks.

Masa
----- Original Message -----
From: "Lung-hao Hu" 
To: 
Sent: Saturday, December 31, 2005 6:02 AM
Subject: [mems-talk] Spin a very thin layer of PR


> If I spin a very thin layer PR, will I observe lots of micro-dots on the
> substrate due to the surface tension??
> I just tried to use Polyimide mixing with thinner 1:4 and spin at 4000rpm
for
> 40s on a glass slide.
> But it seems not what I want.
>
> Is there anyone who did this experiment before??
>
> Lung-hao Hu