A novel thermal microprobe is proposed and its operation is theoretically analyzed. The thermal sensitivity of the microprobe is assured by a field emission diode using n-Si/nitrogen doped as a cathode. The cathode layer is placed on the atomic force microscope cantilever on the opposite side of the sharp sensing stylus, thus allowing for both mechanical and thermal maps of the sample to be obtained. A model to characterize the temperature dependence of the emission current has been developed, which shows good agreement to reported experimental data. The current-temperature exponential dependence allows a high temperature sensitivity of the microprobe. The developed model is further used to characterize the thermal microprobe properties and derive design hints.