Posted by Dan (66.122.81.186) on May 22, 2007 at 15:07:33:
In Reply to: Dopant concentration posted by Dan Schurz on May 22, 2007 at 12:34:46:
: How can I find the dopant concentration for two types of 300mm wafers:
: Boron doped "P" type w/resistivity spec's at 1 - 50 ohm, and
: Phosphorous doped "N" type w/resistivity spec's at 1 - 10 ohm
: Thank you.
Thanks for your question. There’s several ways we can help to obtain or measure the carrier concentration of your wafers.
First, you could use our resistivity to carrier concentration calculator found on our technical information page. (solecon.com/sra.htm) The second note down "Converting Resistivity to Carrier Concentration JavaScript Calculator" is a handy html/JavaScript calculator. For 1 ohm-cm it calculates a P concentration of 1.47e16 Si and an N concentration of 4.83e15 Si.
Second, for a more accurate reading, you could send the wafers to us for 4-point probe measurements. The 4PP measures the sheet resistance which we can convert into resistivity. Then you can use the above calculator to convert the actual resistivity instead of the resistivity range into carrier concentrations. The 4PP has accuracy of +/-1% on sheet resistances.
Third, for wafers not having the same concentration all the way through the slice, you could send the wafers to us for 2-point spreading resistance measurements. The sample would be beveled at a steep angle in order to go as far through the slice as possible (within microns of the other side) and a SRA depth profile could be run through any and all layers. Carrier concentration and resistivity versus depth plots would provide information as a function of depth through the slice. SRA has accuracy of +/-15% on bulk resistivity.
If you’re pretty confident the wafers are uniformly doped through the whole slice (as most starting material is) I would recommend the 4-point probe method.
Dan