IN Brief:
- Keysight, the University of Glasgow, NPL and MPI Corporation demonstrated continuous on-wafer measurements from near DC to 250 GHz.
- The test setup combines a PNA-X vector network analyser, frequency extender, source/measure unit and broadband wafer probing.
- A single probe touchdown reduces setup changes that can complicate calibration and broadband device modelling.
Keysight Technologies, the University of Glasgow, the National Physical Laboratory and MPI Corporation have demonstrated continuous on-wafer characterisation of indium phosphide high-electron-mobility transistors from near DC to 250 GHz using a single probe touchdown.
The measurement approach combines Keysight’s PNA-X vector network analyser, a Single-Sweep 250 GHz Frequency Extender and a precision source/measure unit with semiconductor devices and calibration standards produced by the University of Glasgow, MPI broadband wafer probing hardware and NPL metrology methods. Bringing those elements into one measurement chain allows S-parameter data to be gathered across a frequency span that would conventionally require separate setups, recalibration and repeated contact with the device under test.
Changing instrumentation, probe configuration or calibration plane between frequency bands can introduce another source of uncertainty into measurements that ultimately have to describe one transistor. The problem becomes harder as characterisation moves through millimetre-wave frequencies and towards the sub-terahertz region, where measurements taken on separate systems must be reconciled before they can support a broadband device model. Keeping the device under the same probe touchdown preserves a common physical reference throughout the sweep.
The demonstration used InP HEMTs from the University of Glasgow together with on-wafer calibration standards. InP remains important in very high frequency electronics because its material properties support transistor operation beyond frequencies normally addressed by mainstream silicon devices. Characterising those transistors over a broad continuous range allows models to capture behaviour from comparatively low frequencies through to the region where parasitic capacitance, inductance, gain roll-off and transmission effects become dominant.
Keysight’s extender architecture carries vector network analysis beyond the coaxial frequency range while retaining the phase and magnitude information required for S-parameter measurements. Broadband source power calibration and source filtering are incorporated into the setup so that the millimetre-wave signal reaching the probe tip can be controlled across the sweep, rather than treating the extender and wafer probe as separate measurement systems.
Thierry Locquette, vice president of sales for Europe, the Middle East and Africa at Keysight, said: “Characterizing devices continuously from near DC to 250 GHz in a single sweep can significantly simplify the measurement process for researchers developing next-generation semiconductor technologies. By bringing together expertise in instrumentation, devices, probing, and metrology, this collaboration demonstrates a practical approach to generating the consistent broadband data engineers need to accelerate device development.”
NPL contributed the calibration and traceability needed to separate genuine device behaviour from the response of the measurement system. At frequencies approaching 250 GHz, small changes in probe placement, interconnect geometry and calibration-standard definition can produce significant errors, so extending the nominal frequency range is useful only if the reference plane at the wafer remains credible.
Dr Xiaobang Shang, principal scientist and on-wafer measurement lead at NPL, said: “Accurate on-wafer measurement is essential for developing reliable semiconductor devices, particularly as technologies move further into the millimetre-wave and sub-terahertz frequency ranges. We were pleased to contribute NPL’s high-frequency on-wafer metrology and calibration expertise to this collaboration, helping demonstrate a practical route to consistent broadband device measurements using the state-of-the-art single sweep system.”
Broadband datasets acquired through one integrated system also give modelling teams a more consistent basis for extracting transistor parameters and comparing measured behaviour with electromagnetic and circuit simulations. When datasets are stitched together from different instruments and calibrations, a discontinuity may come from the device or from the boundary between measurement systems, complicating equivalent-circuit fitting and model validation.
MPI Corporation supplied the broadband probing technology and calibration software used to maintain contact between the measurement system and the wafer. Matthew White, director of business development at MPI Corporation, said: “Extending on-wafer characterization to 250 GHz requires the probing, calibration, and measurement platform operating as one seamlessly integrated system. This collaboration demonstrates a practical approach to achieving consistent broadband measurements from near DC to 250 GHz with a single probe touchdown, helping researchers simplify characterization and accelerate device development with great confidence.”
The work is being presented during European Microwave Week 2026 in London, where Keysight’s programme includes a session on initial calibration and measurement results from a wafer-level system spanning 100 kHz to 250 GHz. The demonstration takes the company’s 250 GHz extender hardware into a complete device-characterisation workflow using semiconductor structures, wafer probing and traceable metrology within the same measurement chain.
