While other possibities exist, it may be that the relatively heavily doped
substrate (1e17/ cm3) simply up-diffused and whipped out the boron layer.

Roger Brennan
110 Jeffries Cove
Rocky Mount NC 27804
(252) 442-9612
rogerbr@earthlink.net



-----Original Message-----
From: mems-talk-bounces+rogerbr=earthlink.net@memsnet.org
[mailto:mems-talk-bounces+rogerbr=earthlink.net@memsnet.org]On Behalf Of
Dau Thanh Van
Sent: Tuesday, April 06, 2004 8:15 AM
To: 'General MEMS discussion'
Subject: [mems-talk] Light Boron diffusion in silicon


Hello everybody,

I recently tried to lighly diffused silicon by Boron. The expected
concentration is around 5e17 atoms/cm3. I reduced the temperature to 800C,
and pre-diffused in 15 minutes. For drive-in, I made at 1100C/30minutes. I
estimated the concentration should be 1e18 atoms/cm3 by Frick's law.
However, after the process, I can not measure the sheet resistance of doped
wafer.
The based concentration of the n-type wafer is 1e17 atoms/cm3, and I doped
it succesfully with the prediffusion temperature of 1000C.
Is boron solubility a problem, or the based concentration too high?
By the way, I can not dope the silicon by ion implantation method here. I
really appreciate any ideas or suggestions.
Best regards


==============
Dau Thanh Van
Ritsumeikan Uni.
==============




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