High-temperature semiconductor transistor integrated circuit (IC) electronic chips capable of prolonged 500 °C operation would enable important advancements in the sensing and control of combustion in jet engines, making them cleaner, safer, and more fuel efficient. In addition, such chips would be keys to the long-term operation of scientific probes on or near the scorching 460 °C surface of Venus. Although there have been reports of short-term (less than 10 hr) semiconductor IC operation at 500 °C or above, much longer operating times are needed for these and other beneficial high-temperature electronics applications. Toward this end, the NASA Glenn Research Center has been pioneering silicon carbide (SiC) transistor IC electronics technology targeted for greatly prolonged operational durability at 500 °C. These efforts previously demonstrated important foundational building blocks for 500 °C durable ICs (including high-temperature metal-semiconductor contacts (ref. 1), packaging (ref. 2), and discrete transistors (ref. 3)) and a simple inverting amplifier stage made from discrete resistors and transistors connected together on a circuit board (ref. 4).
Building on this foundation, civil servants and Ohio Aerospace Institute (OAI) researchers at Glenn designed, fabricated, and electrically operated a differential-amplifier IC chip continuously at 500 °C for more than 2000 hr. This is the first semiconductor transistor IC to demonstrate stable continuous electrical operation in such a harsh high-temperature oxidizing air environment over such an extended period of time.
Silicon carbide (SiC) differential amplifier IC.
Circuit power supply voltage, VDD, 40 V;
circuit resistors, RD = RSS = 545 Ω.
Long description of figure 1.
The heart of the SiC differential-amplifier IC chip, showing the two
6H-SiC junction field effect transistors (on the right side) and part
of the three 6H-SiC resistors (on the left side) that make up the IC.
Long description of figure 2.
The differential-amplifier IC consisted of two transistors and three resistors integrated (i.e., interconnected to each other to form the circuit) over less than half a square millimeter of area of a single SiC chip. The circuit schematic diagram shows the differential amplifier, and the optical microscope photograph shows the differential amplifier on the surface of the SiC chip as it appeared prior to packaging.
The following graph plots the voltage-versus-time waveforms (recorded on a digitizing oscilloscope) that verified proper operation of the differential-amplifier IC. The IC amplifies a 1-kHz sine wave input test signal with 1-V peak-to-peak amplitude (black signal in the graph) into a 3-V peak-to-peak amplitude sine wave output signal. The output signals recorded from the 1st and 2000th hours of the 500 °C test also are shown. The fact that the 1- and 2000-hr output waveforms fall on top of each other demonstrates that no appreciable degradation of circuit functionality occurred despite prolonged operation in the harsh 500 °C ambient environment.
Voltage versus time waveforms recorded by a digitizing oscilloscope
showing that the IC sitting in an oven at 500 °C amplifies a
1-V-amplitude sine wave input test signal into a 3-V-amplitude
sine wave output wave at the start (1st hour) and end
(2000th hour) of the harsh-environment durability test.
Long description of figure 3.
This demonstration of 500 °C transistor IC operational durability represents an important step toward significantly expanding the operational envelope of sensor signal-processing electronics for harsh environments. An important next step in the development of 500 °C IC technology is to greatly increase the single-chip transistor count, which in turn, would enable much greater 500 °C IC functionality beyond simple signal amplification.
Find out more about silicon carbide electronics research at Glenn: http://www.grc.nasa.gov/WWW/SiC/
Glenn Contacts: Dr. Philip G. Neudeck, 216-433-8902, Philip.G.Neudeck@nasa.gov, Dr. Glenn M. Beheim, 216-433-3847, Glenn.M.Beheim@nasa.govLast updated: November 7, 2008
Responsible NASA Official:
Gynelle.C.Steele@nasa.gov, 216-433-8258
Point of contact for NASA Glenn's Research & Technology reports: Cynthia.L.Dreibelbis@nasa.gov, 216-433-2912
Web page curator: Nancy.L.Obryan@nasa.gov (Wyle Information Systems, Inc.)
