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Effects of the flow rate of O2 annealing ambient on structural and electrical properties of n+ emitter junctions formed using screen‐printed 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. Copyright © 2012 John Wiley & Sons, Ltd.