Measurement of Transit Time and Related Transistor Characteristics.

Two instruments for transistor delay-time measurements, the vector voltmeter and Sandia bridge, were analyzed and comparative measurements were made on several types of commercial and two special transistors. It was found that extraneous pickup at the measurement frequency can cause large errors in measured delay time. A technique for minimizing these errors was developed and verified for the Sandia bridge by removing the frequency dependence of delay times measured on tiny plug-in R-C networks. Measurements of probe restoring force, probe tip protrusion and lateral motion skating with loading were recorded for special probe assemblies to be used in an automatic wafer prober for measurements on transistors in custom-designed integrated circuit wafers. The data is used to assist in adjusting the probes. A technique was developed for determining the effects of the probe assemblies on transistor measurements made from 0.1 to 2.0 GHz. Each probe assembly may be represented by an equivalent circuit consisting of three unknowns these unknowns are determined by making impedance measurements at the input connectors with the probe tips contacted by combinations of open circuits, short circuits, and resistors of known value. Arrays of such terminations were successfully fabricated and characterized. An S-parameter interlaboratory testing program was developed. The plan calls for six of each of three types of transistors to be measured by participants at frequencies from 0.11 to 2.0 GHz. Additionally, a 10-dB attenuator and R-C networks on TO-72 headers are to be circulated to pinpoint measurement discrepancies. Author