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U. Schmid, S.T. Sheppard, W. Wondrak:
"High Temperature Performance of NMOS Integrated Inverters and Ring Oscillators in 6HSiC";
IEEE Transactions on Electron Devices, Vol. 47 (2000), 4; 687 - 691.

Electrical characterization up to 573 K is performed on integrated inverters with different beta ratios and 17-stage ring oscillators based on SiC NMOS technology. These devices are fabricated on a p-type 6H-SiC epitaxial layer with a doping concentration of NA=1·10 16 cm-3. The n+ source/drain regions and buried channels for depletion-mode load transistors are achieved by ion implantation of nitrogen. Direct current measurements of the inverters with a 5 V power supply yield proper output levels and acceptable noise margins both at 303 and 573 K. Dynamic measurements with square waves show the full voltage swing up to 5 kHz in this temperature range. The 17-stage ring oscillators, driven by a 5.5 V power supply, show an oscillator frequency of 625 kHz at 303 K, which corresponds to a 47 ns delay per inverter stage. This time constant increases only to 59 ns at 573 K. The temperature drift of the measured output signal is well below 30% up to this elevated temperatures. During 20 heat cycles up to 573 K in air, no measurable drift in circuit parameters occurred. In addition, only a slight dependence of the oscillator frequency on supply voltage is observed

http://dx.doi.org/10.1109/16.830980