Equipment for On-Wafer Testing From 220 to 325 GHz

On-wafer vector network analysis of semiconductors is extended to higher frequencies.

A system of electronic instrumentation, constituting the equivalent of a two-port vector network analyzer, has been developed for use in on-wafer measurement of key electrical characteristics of semiconductor devices at frequencies from 220 to 325 GHz. A prior system designed according to similar principles was reported in “Equipment for On-Wafer Testing at Frequencies Up to 220 GHz” (NPO-20760), NASA Tech Briefs, Vol. 25, No. 11 (November 2001), page 42. As one would expect, a major source of difficulty in progressing to the present higherfrequency- range system was the need for greater mechanical precision as wavelengths shorten into the millimeter range, approaching the scale of mechanical tolerances of prior systems.

The system (see figure) includes both commercial off-the-shelf and custom equipment. As in the system of the cited prior article, the equipment includes test sets that are extended versions of commercial network analyzers that function in a lower frequency range. The extension to the higher frequency range is accomplished by use of custom frequency-extension modules that contain frequency multipliers and harmonic mixers. On-wafer measurement is made possible by waveguide wafer probes that were custom designed and built for this wavelength range, plus an onwafer calibration substrate designed for use with these probes. In this case, the calibration substrate was specially fabricated by laser milling. The system was used to make the first on-wafer measurements of a semiconductor device in the frequency range from 220 to 320 GHz. Some of the measurement results showed that the device had gain. A Probe Station and Test Sets assembled from commercial-off-theshelf and custom components enable on-wafer measurement of electrical characteristics of devices in the previously inaccessible frequency range of 220 to 325 GHz.

This work was done by Lorene Samoska, Alejandro Peralta, Douglas Dawson, and Karen Lee of Caltech; Greg Boll of GGB Industries; and Chuck Oleson of Oleson Microwave Labs for NASA’s Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free online at www.techbriefs.com/tsp under the Semiconductors & ICs category. NPO-40955