Experimental determination of self-heating in submicrometer MOS transistors operated in a liquid-helium ambient

Self-heating (SH) in submicrometer CMOS transistors operated at liquid-helium temperature and under different bias conditions was experimentally verified by measuring the temperature T/sub Si/ in the proximity of the device. T/sub Si/ was measured by using a silicon resistor, placed in the same bulk nearby the device under test, as a temperature sensor. It was found that the heat generated by the NMOS transistor of a CMOS inverter structure penetrates deep into the substrate and reduces very strongly the n-well impedance, giving rise to large variations in the kink of the I/sub drain/-V/sub drain/ characteristics of the neighbor PMOS transistor. Experimental results confirm that SH must not be underestimated when characterizing and modeling low-temperature device operation.<
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