Posted by Dan (66.122.81.186) on March 16, 2010 at 14:11:09:
In Reply to: Sample with insulator film (silicon nitride) posted by Natalita Nursam on March 15, 2010 at 19:46:48:
: Hi,
: I need to get carrier concentration profiles of heavily doped boron emitter on c-Si substrates with a 70 nm plasma silicon nitride film on top.
: My questions are:
: 1. Is it necessary to etch the silicon nitride film prior to the 2 point probe measurement? the same question applies for the case of silicon oxide coated sample.
In this case, no. We can usually bevel through a thin nitride film without difficulty. Thick passivation nitride is another story. Because it is much thicker and harder than the silicon below it, it causes trouble with beveling so we ask you remove passivation nitride.
Silicon oxide is not a problem regardless of thickness. If it creates problems with the sample preparation, we can strip the oxide using HF.
: 2. Can we use SRP to get the dopant concentration (in particularly boron) that may exist on the insulator film such as silicon nitride or oxide?
No. The SR probe can measure resistances from 1e0ohms up to 1e9ohms. The resistances are then compared to those measured on known resistivity standards of Silicon or Germanium material to determine the resistivity. The resistivity is then converted to carrier concentration using bulk mobility values.
Nitrides or oxides have resistances higher than our machines will read. If we could measure the resistances we still would need known resistivity material to calibrate those values to and then we'd have to have the appropriate mobilities to convert the resistivities into carrier concentrations.
Also, your c-Si substrates would need to be mirror polished for SRP. We bevel the samples at an angle less than perpendicular to spread the depth into a distance across the surface. So the surface needs to be planar. We have trouble with multi-crystalline wafers and even some mono-crystalline wafers if they haven’t been mirror polished.
Dan