For silicon, one quick way to convert resistivity to carrier concentration
is to go to the Solecon Labs website (www.solecon.com); select the first
option, "SRA"; then select the 2nd option under technical
notes--"Converting Resistivity to Carrier Concentration JavaScript
Calculator. Try It!!"
(It is much easier than it sounds!)

Because of carrier mobility differences, P and N concentrations are not the
same.  In this case, you want "P".  For instance, 1 ohm-cm p-type = 1.5E16
holes/cm3  and 40 ohm-cm = 3.3E14 holes/cm3.  Quite a spread, isn't it?
 (The high end of the spec is probably best for what you want to check.)

To get an idea of the wafers "real" bulk resistivity, measure it with a
four-point probe.  The relationship here is sheet resistance (ohms/square)
= bulk resistivity (ohm-cm) / thickness of wafer (in cm).  Do the math.
 For the record, four-point probes actually measure V/I (ohms)  BUT most
displays will give you sheet res (ohms/sq) directly.   Sheet resistance =
4.53 V/I.

After you have doped the wafer, strip off any oxide and four-point probe
the wafer.  If you get a "reasonable" sheet resistance, you might want to
send a sample to Solecon Labs for a depth profile.

Good luck and feel free to contact me.


Roger Brennan (formerly with Solecon Labs)
8710 Gardners School Road
Stantonburg, NC 27883
(252) 238-3377
[email protected]


-----Original Message-----
From:   amith [SMTP:[email protected]]
Sent:   Monday, December 02, 2002 3:14 PM
To:     [email protected]
Subject:        [mems-talk] Diffusion time of N-type spin-on-dopant on P-type
wafer   and Background concentration of a p-type wafer

Dear MEMS group,
  Can any one please tell me how to find out the time for diffusing
10um N-type spin-on-liquid dopant on P-type Si substrate.Do we need to
use any software to run. or its just the substitution of formulas.

  I have one more question how can we know the background
concentration of a wafer. because i got 4inch p-type (100) wafers of
resistivity 1-40 ohms/cm. I have no idea of finding the background
concentration (Nd) with the data supplied.

Thanking you,
Regards,
Amith K Arigapudi.

_______________________________________________
[email protected] mailing list: to unsubscribe or change your list
options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
Hosted by the MEMS Exchange, providers of MEMS processing services.
Visit us at http://www.memsnet.org/