Advancements in Metrology for Cryogenic and Millimeter-Wave Technologies

Author: ORCID icon
Eller, Michael, Electrical Engineering - School of Engineering and Applied Science, University of Virginia
Weikle, Robert, EN-Elec & Comp Engr Dept, University of Virginia

The terahertz (THz) region of the electromagnetic spectrum contains a vast amount of
untapped potential for many technological applications in areas such as astronomy,
imaging, non-destructive evaluation, communications, and defense; however, there is a lack
of high-power sources and sensitive receivers in this region. This is commonly referred to
as the “THz Gap.” The design, measurement, and characterization of these circuits is often
complex and labor-intensive due to the unique challenges created in this band, which sits
uniquely between traditional electronics and optics.
This dissertation is a collection of four distinct measurement and metrology-based
research efforts: a micromachined ultrathin silicon DC probe for cryogenic measurements
(1), an open-source implementation of microwave noise wave analysis (2), broadband on-
wafer measurements of 35nm InP HEMT Devices and MMICs (3), and the first
demonstration of WR-5.1 cryogenic on-wafer scattering parameter and noise figure
measurements of active devices (4).
1. For cryogenic devices, such as the SIS junction widely used in radio astronomy, even
simple DC characterization is a challenging task. These chips must be lapped,
thinned, and mounted to a carrier for chip-by-chip screening, an approach that is
time intensive, requires additional processing of the chip before evaluation, and is
not practical for screening entire wafers containing thousands of devices. A new DC
cryogenic on-wafer probe capable of 4K measurements has been designed,
fabricated, and demonstrated. This probe technology will enable whole-wafer
cryogenic screening using a silicon-on-insulator (SOI) probe platform.
2. The study of electrical noise is a very broad and challenging field, especially at
higher frequencies. The work presented in this chapter is the most robust
implementation of noise analysis in open-source software to date. scikit-rf or skrf
(see: is an open-source microwave network

analysis Python package for network creation, analysis, and calibration. skrf is a
popular free software tool and is maintained with the collaboration of international
scientists and engineers. At the time of writing, the implementation of noise wave
analysis is still waiting to be merged with the main branch (see:
3. One of the most important technologies enabling advancement in the terahertz
region of the electromagnetic spectrum is the HEMT. The high electron mobility
transistor (HEMT) has emerged in the past few decades as the dominant technology
for microwave, millimeter-wave, and sub-millimeter wave low-noise circuits.
HEMTs are heterojunction devices with exceptional switching speeds, high gain, and
fabrication techniques compatible with monolithic processing, making them
excellent devices for high frequency low-noise and power amplifiers, mixers, and
oscillators. In collaboration with Northrop Grumman Space Systems, new
broadband (DC-220GHz) measurements and parameter extractions of the 35nm
indium-phosphide (InP) HEMT and HEMT-based monolithic microwave integrated
circuit (MMIC) low noise amplifiers (LNAs) were performed.
4. The first demonstration of WR-5.1 cryogenic on-wafer scattering parameter and
noise figure measurements of active circuits were performed. A new noise figure
measurement system is described, and single-sideband measurements are achieved
through the use of sideband cancellation.

PHD (Doctor of Philosophy)
terahertz, HEMT, on-wafer, metrology, millimeter-wave, submillimeter-wave, cryogenic, noise waves
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