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How to Measure the Sheet Resistance of Semiconductors

Electricity is due to the flow of charged particles through metallic wires. As electrons flow, they scatter off one another and off the side of the wire, reducing the effective current. These scattering events combine to form a macroscopic quantity that is known as the resistance of the wire and it can typically be measured with multimeter. A related quantity is the sheet resistance which is defined as being the resistivity divided by the thickness of the semiconductor.

Things You'll Need

Semiconductor specification sheet
Digital calipers

Instructions

- 1
  Read the specification sheet supplied with the semiconducting material. All semiconductor manufacturers supply a specification sheet and this will have the resistivity of the material. The resistivity of a material is a measure of how much scattering occurs within a fixed volume. The units of resistivity are usually quoted in Ohm meters.
- 2
  Measure the thickness of the semiconducting material using calipers. Open the caliper jaws and carefully place the semiconducting material between them. Carefully close the jaws, so that the upper and lower jaws are making contact with the semiconducting material. The digital screen indicates the measured thickness. Take a note of the thickness in units of meters.
- 3
  Calculate the sheet resistance. The sheet resistance is equal to the resistivity divided by the thickness:
  
  Rsheet = Rho / t
  
  Where Rho is the resistivity in Ohm meters, and t is thickness in meters. The units of sheet resistance are Ohms per square.

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