Do you get evidence of a p-n junction if you omit the SiO2 step?

Evidence of a p-n junction might be obtained by four-point probing,
bevel&stain, or spreading resistance.

Regards,


Roger Brennan
Applications Director
Solecon Labs
770 Trademark Drive
Reno, NV 89521-5926
roger@Solecon.com
775-853-5900 ext 108


-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org]On Behalf Of Tao
Sent: Thursday, August 31, 2006 2:30 PM
To: General MEMS discussion
Subject: [mems-talk] Diffusion mask


Dear ALL,
    I have some problems with doping boron. I use PECVD silicon di-oxide
(500-600nm) as a diffusion mask. The procedure is that
1) Spin Borofilm 100 on wafer (N-type, 2-5 ohm cm)
2) Diffusion at 1000 degree C for 30min
3) Clean the source, and annealing at 1100 degree C for 2hours.

After these steps, I find there is no pn junction. So I guess it might
be the problem of diffusion mask. Does anyone have experience with that?
The recipe of PECVD SiO2 is:
Ar : 10sccm
O2: 20sccm
MicroWave : 300W
RF power: 0W
Chunk Temperature: 19 degree C
pressure: 20mT