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[relative to Semiconductor Applications] Four point probe based instruments use a long established technique to
measure the average resistance of a thin layer or sheet by passing
current through the outside two points of the probe and measuring the
voltage across the inside two points.
If the spacing between the probe points is constant, and the
conducting film thickness is less than 40% of the spacing, and the
edges of the film are more than 4 times the spacing distance from the
measurement point, the average resistance of the film or the sheet
resistance is given by:
Rs = 4.53 x V/I The thickness of the film (in cm) and its resistivity (in ohm cm) are related to Rs by: Rs = resistivity/thickness Therefore one can calculate the resistivity if the thickness of a film
is known, or one may calculate the thickness if the resistivity is
known.
Ohms-per-square: The unit of measurement when measuring the resistance of a thin film of a material using the four point probe technique. It is equal to the resistance between two electrodes on opposite sides of a
theoretical square. The size of the square is unimportant. |
| Four-Point-Probes is a division of Bridge Technology. To request further information please call Bridge Technology at (480) 988-2256 or send e-mail to Larry Bridge at: sales@bridgetec.com |
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