1/f Noise Reduction in Cryogenic Highly Compensated Silicon Thermistors

The thermal sensitivity and Low Frequency Noise (LFN) of compensation doped Silicon-On-Insulator (SOI) resistors are studied experimentally, down to the cryogenic regime. A high compensation nominal ratio K = N _A /N _D of 0.82 is compared with uncompensated and partially compensated configurations, using Phosphorus and Boron as dopant species. The Temperature Coefficient of Resistance (TCR) reaches -2.7%/K at 80 K, for an effective compensation ratio close to 0.98 considering incomplete dopant ionization. The measurements reveal a low LFN with a nearly frequency-independent spectrum, far from the classical 1/f trend observed in uncompensated silicon. The mean value of the Hooge constant on the highly compensated silicon sample equals 3.15 × 10 ^-4 at 300 K and 4.50 × 10 ^-5 at 80 K. The normalized LFN at 80 K does not depend on the resistor length and thereby seems independent of the volume. Such high performance thermistors represent an attractive, mature and affordable solution for high performance thermal sensing.