Specific Process Knowledge/Characterization/Four-Point Probe: Difference between revisions

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 The sheet resistance can then be calculated using the equation below:
 [[Image:Rs.PNG |200x200px|Unit ohms/square]]
-      Unit ohms/square
+This equation is only valid if: i) the material being tested is no thicker than 40% of the spacing between the probes, and ii) the lateral size of the sample is sufficiently large. If this is not the case, then geometric correction factors are needed to account for the size, shape, and thickness of the sample.
-This equation is only valid if: i) the material being tested is no thicker than 40% of the spacing between the probes, and ii) the lateral size of the sample is sufficiently large. If this is not the case, then geometric correction factors are needed to account for the size, shape, and thickness of the sample.
 Bulk resistivity for wafers and films = sheet resistance x wafer thickness in cm   (Unit ohm.cm)
 Bulk resistivity for a semi-infinite volume = 2 x π x S x V/I  where is S is the probe spacing in cm (Unit ohm.cm)
 A sample is usually defined as a “semi-infinite volume” if it extends to infinity in all directions below a plane on which four probes are located.