High temperature performance of NMOS integrated inverters and ring oscillators in 6H-SiC

Electrical characterization up to 573K 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 laye r with a doping concentration of N-A approximate to 1.10(16) cm(-3).The n() source/drain regions and buried channels for depletion-mode load transist ors are achieved by ion implantation of nitrogen. Direct current measuremen ts of the inverters with a 5 V power supply field proper output levels and acceptable noise margins both at 303 and 573K. Dynamic measurements with sq uare wares show the full voltage swing up to 5 kHz in this temperature rang e. The 17-stage ring oscillators, driven by a 5.5 V power supply, show an o scillator frequency of 625 kHz at 303K, which corresponds to a 47 ns delay per inverter stage. This time constant increases only to 59 ns at 573K, The temperature drift of the measured output signal is well below 30% up to th is elevated temperatures. During 20 heat cycles up to 573K in air, no measu rable drift in circuit parameters occured, In addition, only a slight depen dence of the oscillator frequency on supply voltage is observed.