Effects of Gas Mixture Flow on POCl₃ Emitters in P-Type Silicon Solar Cells

We investigated the effect of flow rates of a gas mixture on characteristics of the POCl₃ emitter including sheet resistance, wafer-to-wafer uniformity, in-wafer uniformity, and implied open circuit voltage in addition to flow velocity simulation. First, the distribution graph of sheet resistance demonstrated that sheet resistance increases toward both ends of the tube by decreased flow velocity. Second, the in-wafer uniformity improved from 90.8% to 92.6% and sheet resistance increased from 79.6 Ω/sq to 157.8 Ω/sq with a decreasing total flow rate, caused by decreased source gas and flow velocity. Third, the reduction in the total gas flow with constant flow rates of source gases caused the in-wafer uniformity to improve to 93.1% because of increased source gas exposure duration. Sheet resistance decreased to 63.11 Ω/sq and wafer-to-wafer uniformity decreased to 91.8%. The experiment with a further reduced total flow rate exhibited an increase in in-wafer uniformity to 94.9% and a decrease in wafer-to-wafer uniformity to 89.3% because of the infinite source condition. However, a uniformity zone was fixed for all flow conditions. From this results, the quality of the emitters was improved by increased wafer-to-wafer uniformity and in-wafer uniformity achieving the highest implied open circuit voltage of 669 mV with 93% wafer-to-wafer uniformity and 90.8% in-wafer uniformity.