Excellent surface passivation with a localised back surface field (LBSF) formation is the key parameter for increasing the efficiency of PERC cells. In this regard, the additional use of rear multi-stack passivation layers (Al2O3/SiNX) and local laser opening of the LBSF increase the production cost. In addition, these stacked layers and the laser process require additional tools, which creates a compatibility barrier for studies conducted in small-scale industrial laboratories. Rear multi-stack passivation layers (Al2O3/SiNX) and a front SiNX anti-reflection coating (ARC) layer were changed using a one-step thermal oxidation process. The emitter doping and thermal SiO2 oxidation layer were optimised for the front ARC and rear passivation layer. The formation mechanism of the LBSF was investigated by varying the firing conditions and the Al dot size. Scanning electron microscopy images confirmed the thickness of the LBSF. The fabricated cell exhibited an efficiency of 20.05% with a fill factor (FF) of 78%, a current density (J(SC)) of 39.3 mA/cm(2), and an open-circuit voltage (V-OC) of 655 mV under a spectral condition of AM 1.5G. A significant improvement in the recombination current density (J(0)) (314 fA/cm(2)) was achieved as compared with the fire-through full BSF solar-cell process (933 fA/cm(2)).