Hi Kirt
  The problem is the  size of the samples are of the order of microns. about
20-50 microns.
  Thanks


Kirt Williams  wrote:
  Since you're making a four-probe measurent, the dimensions of the metal
contacts are probably on the order of a millimeter.
This is large enough for shadow masking:
1. Make a mask from a thin sheet of material with holes where you want the
pad.
2. Firmly clip the mask to the organic substrate. It is critical that there
not be a gap between the shadow mask and the substrate. And you don't want
it to shift during deposition.
3. Evaporate or sputter metal.
4. Remove mask and you're done.

The hardest part is making the shadow mask. You may get useful results with
pinholes in piece of foil or drilled holes in sheet metal.
For more-complex shapes, I've used DRIE to make patterns in a silicon wafer.

--Kirt Williams