Silicon: A Revenant Thermoelectric Material for Energy Autonomous Integrated Circuits

Si integrated circuits (ICs) for internet-of-things (IoT) electronics must carry an energy source when embedded in dark and inaccessible environments. Microelectronic thermoelectric generators (µTEGs) can provide such energy autonomy from a thermal gradient. Most research on TE technology focuses on high ZT materials, which often contain toxic or expensive elements incompatible with Si IC processing. We report on Si-based µTEGs fabricated on a standard Si IC process line. Although Si has poor ZT, these µTEGs generate power per area per square of temperature difference, ∆T, > 80 µWcm^–2K^–2, better than most high ZT TEGs. Our Si µTEGs generate voltages > 1.5 V with > 1 µA current using ∆T ~ 20 °C, sufficient to energize existing IoT ICs. These µTEGs can be integrated on-chip with the ICs they support. Our approach applies device physics to optimize power and voltage generated per area, rather than efficiency. This exploits the ability of Si processing to fabricate thermopiles with a large number of TE elements in a small area, producing high power and voltage density despite low efficiency per TE element. Results on power and voltage generation and physics-based models for optimizing performance will be presented.