Effects of the flow rate of O₂ annealing ambient on structural and electrical properties of n+ emitter junctions formed using screenprinted phosphorus diffusion process

We have investigated the effects of the flow rate of O₂ annealing ambient on the structural and electrical properties of the emitters with n+/p junctions formed using the screen printing of phosphorus (P) dopant paste, followed by O₂ annealing. The reaction between P-paste and Si led to the formation of phosphorus silicate glass layer, of which P atoms were mostly segregated in surface and interface regions. The sheet resistance of the screen-printed n+ emitters formed under O₂ flow rate of 5 l/min (LPM) was lower than that of 1 LPM. The recombination mechanism dominated the current transport in the forward bias regions of the screen-printed n+ emitter, regardless of O₂ flow rate. The n+ emitter formed under O₂ flow rates of 5 LPM exhibited better rectification behavior with low reverse leakage, as compared with that of 1 LPM. The formation of thicker phosphorus silicate glass film caused by the increase in the O₂ flow rate resulted in the increase in the equilibrium concentration of Si interstitials in bulk Si and provided more P atoms being incorporated in n+/p emitter junction. The increases in maximum concentration of P atoms and junction depth caused by the increase in the O₂ flow rate could be responsible for superior junction quality of n+ emitter formed under O₂ flow rates of 5 LPM.