The objective of this program is to develop the first terahertz frequency (>0.5 THz) on-wafer probe station in the world. The proposed instrument development plan will assemble a full two-port terahertz frequency vector network analyzer (VNA) system with frequency extension modules mounted to a probing platform. The wafer probes, fabricated by the University of Virginia, will be mounted directly to the frequency extension modules in order to realize a complete terahertz-frequency on-wafer probe station operating from 500 to 750 GHz. The intellectual merit is that the terahertz frequency range has enormous potential for both scientific discoveries in the areas of radio astronomy, chemical spectroscopy, and material characterization as well as applications in atmospheric ozone monitoring, concealed weapons and chemical / biological hazards detection, and compact-range radar systems. However, a significant hurdle has been the inability to rapidly characterize circuits and devices through on-wafer testing. Current test procedures involve time-consuming development of connectorized prototypes or free-space measurements. The broader impacts are benefiting the wider scientific and engineering communities by enabling the rapid advances in device technology required in order to realize terahertz integrated circuits for advanced imaging systems, stand-off detection of harmful chemicals and explosives and short-range communication that is far beyond what is now possible. In addition, the development of a terahertz frequency probe station will provide a tremendous opportunity for motivating young prospective engineers to enter the field of engineering by demonstrating the progress that can be made towards critical applications through an engineering education.
The objective of this program was to develop a terahertz frequency (>0.5 THz) on-wafer probe station. The developed instrument includes a full two-port terahertz frequency vector network analyzer (VNA) system with frequency extension modules mounted to a probing platform. The wafer probes, fabricated by the University of Virginia, are mounted directly to the frequency extension modules in order to realize a complete terahertz-frequency on-wafer probe station operating from 500 to 750 GHz. The intellectual merit is that the terahertz frequency range has enormous potential for both scientific discoveries in the areas of radio astronomy, chemical spectroscopy, and material characterization as well as applications in atmospheric ozone monitoring, concealed weapons and chemical / biological hazards detection, and compact-range radar systems. However, a significant hurdle has been the inability to rapidly characterize circuits and devices through on-wafer testing. Current test procedures involve time-consuming development of connectorized prototypes or free-space measurements. The THz frequency on-wafer probe station that has been developed at the University of Virginia consists of an Agilent AT-N5245A 10 MHz to 50 GHz PNA-X vector network analyzer with Virginia Diodes Inc. WR1.5 (500-750 GHz) frequency extension modules. The frequency extension modules are mounted on a Cascade Microtech PA200 probe station with large-area positioners. The WR1.5 wafer probes, fabricated at UVA, mount directly to the frequency extension modules. The completed system is shown in Figure 1. Initial measurements performed to verify the system performance include thru-reflect-line (TRL) calibrations and measurements of GaAs diode circuits fabricated at UVA. Figure 2 shows measurements of both a thru-line (on the right side) and a set of offset CPW shorts (on the left side). The broader impacts are benefiting the wider scientific and engineering communities by enabling the rapid advances in device technology required in order to realize terahertz integrated circuits for advanced imaging systems, stand-off detection of harmful chemicals and explosives and short-range communication that is far beyond what was previously possible. The initial applications that the THz probe station have been used for include measurement of GaAs diodes and vanadium dioxide devices that are being investigated for use as switches. Figure 3 shows measurements of both of these devices – the VO2 is measured from 500-750 GHz while the GaAs diode is measured from 325-500 GHz. Future collaborations have been initiated with researchers from around the world. These collaborations will involve visits to the facility in Charlottesville, VA in order to facilitate measurements of devices fabricated by the visiting scientists.
