Photograph of high-temperature probe station and instrumentation.
Long description.
A high-temperature measurement system capable of performing on-wafer microwave testing of semiconductor devices has been developed at the NASA Glenn Research Center. This high-temperature probe station can characterize active and passive devices and circuits at temperatures ranging from room temperature to above 500 °C. The heating system uses a ceramic heater mounted on an insulating block of NASA shuttle tile material. The temperature is adjusted by a simple graphical computer interface and is automatically controlled by the software-based feedback loop. The system is used with a Hewlett-Packard 8510C Network Analyzer (Palo Alto, CA) to measure scattering parameters over a frequency range of 1 to 50 GHz. The microwave probes, cables, and inspection microscope are all shielded to protect from heat damage. The high-temperature probe station has been used successfully to characterize gold transmission lines on silicon carbide (SiC) at temperatures up to 540 °C.
The ability to perform microwave tests at high temperatures is becoming necessary. There is now a need for sensors and communication circuits that can operate at 500 °C and above for aircraft engine development and monitoring during flight. To address this need, researchers have fabricated devices using wide bandgap semiconductors such as SiC with targeted operating temperatures of 500 to 600 °C. However, the microwave properties of these devices often change drastically with temperature, so any designs that are intended to be used in such an environment must be characterized at high temperatures. For some reliability, lifetime, and direct-current testing, the device under test can be packaged and characterized in an oven. However, for RF and microwave measurements, it is usually not possible to establish a calibrated reference plane at the device terminals within a package. In addition, the characteristics of the package would vary over a 500 °C temperature range, and this would have to be accounted for when the data were analyzed. A high-temperature probe station allows circuits and devices to be characterized through on-wafer measurements across a broad temperature range with known reference plane.
The conventional, commercially available thermal wafer-probe stations that are used to evaluate microwave devices across a controlled temperature range have a typical upper limit of 200 °C. Standalone thermal heating chucks are available with an extended upper temperature range of 300 to 400 °C. To effectively characterize devices at temperatures up to and surpassing 500 °C, Glenn researchers developed a custom probe station. In the past, custom probe stations have been developed to test devices under other extreme environments, such as cryogenic temperatures as low as 37 K. Similarly, this custom probe station was specifically modified for high-temperature use. It allows devices to be measured quickly and flexibly, without the use of wire bonds and test fixtures.
Microwave probes and test circuit on heater.
Long description.
Glenn contact: Alan N. Downey, 216-433-3508, Alan.N.Downey@nasa.gov
Authors: Alan N. Downey and Zachary D. Schwartz
Headquarters program office: OAT
Programs/Projects: UEET, Intelligent Propulsion Controls
Last updated: January 20, 2005
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