Direct observation of self-heating in III–V gate-all-around nanowire MOSFETs

Gate-all-around MOSFETs use multiple nanowires to achieve target ION, along with excellent 3D electrostatic control of the channel. Although self-heating effect (SHE) has been a persistent concern, the existing characterization methods, based on indirect measure of mobility and specialized test structures, do not offer adequate spatio-temporal resolution. In this paper, we develop an ultra-fast, high resolution thermo-reflectance (TR) imaging technique to (i) directly observe the increase in local surface temperature of the GAA-FET with different number of nanowires (NWs), (ii) characterize/interpret the time constants of heating and cooling through high resolution transient measurements, (iii) identify critical paths for heat dissipation, and (iv) detect in-situ time-dependent breakdown of individual NW. Our approach also allows indirect imaging of quasi-ballistic transport and corresponding drain/source asymmetry of self-heating. Combined with the complementary approaches that probe the internal temperature of the NW, the TR-images offer a high resolution map of self-heating in the surround-gate devices with unprecedented precision, necessary for validation of electro-thermal models and optimization of devices and circuits.