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

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 Sheet Resistivity = Sheet Resistance = Surface Resistivity = Surface Resistance
+'''Limits of Measurement Capability'''
+.    The material must be capable of being probed, i.e. the probes must be able to make ohmic contact with the material e.g. Germanium, Silicon and metals. Materials such as Gallium Arsenide cannot normally be probed unless it is doped and measured with special measuring techniques such as that in the Four Dimensions Inc. GaAs probe.
+.    Very low resistivity material e.g. aluminum, gold, platinum may require the maximum current from the current source to achieve a reading on the digital voltage display. Only very thin films from 10’s nm up to 1 micron thickness can be measured. Sample with expected sheet resistance less than 1 ohm/square may not possible to measure.
+.    High resistivity material e.g. ion-implanted Silicon wafer, silicon on sapphire, can be measured using very low current (about 1uA or less) and trying to avoid a greater voltage indication than 200mV. Probably sheet resistance up to 107 ohms/square can be measured.
+.    Low measurement result could be from electrical noise due to poor contact condition, thermally induced voltages, actinic effects, offset voltages produced by the devices in the current source etc.