## 3 Results and Discussion  
To optimize the pre-diffusion process and to form a uniform emitter layer, the pre-diffusion process was performed for 12 min, and the process temperature was increased from 780 to 830 \({}^{\circ}\)C in 10 \({}^{\circ}\)C intervals. The drive-in process was performed for 14 min, and the process temperature was increased from 810 to 890 \({}^{\circ}\)C in 20 \({}^{\circ}\)C intervals. Figure 1 shows the graph of the surface resistance in the emitter layer with a temperature difference between the pre-deposition and diffusion processes. The surface resistances were measured at five points of the wafer where the emitter layer was formed, and the change in the sheet resistance depending on the pre-deposition and drive-in temperatures showed a similar trend. The sheet resistance decreased with the increasing temperatures of the deposition and drive-in processes because the higher the pre-deposition temperature, the greater the influence of diffusion of dopants deposited on the wafer surface. At a drive-in temperature of 810 \({}^{\circ}\)C, the measured resistance value was high and unsuitable for the diode of a solar cell. The diffusion equation can be expressed as \(J_{diff}=-D\frac{\partial N}{\partial X}\), where \(J_{diff}\) is the flux (g/cm\({}^{2}\)-sec), \(N\) is the impurity concentration, and \(D\) is the diffusion coefficient. \(D\) is the proportionality constant that was applied because the dependence of temperature on thermal motion varies depending on the particle type. The formula for \(D\) can be expressed as \(D=D_{0}\exp{(-\frac{E_{A}}{RT})}\), where \(E_{A}\) is the activation energy (J/mol), \(D_{0}\) is the pre-exponential factor, \(k\) is the Boltzmann constant, and \(T\) is the temperature (\(K\)). An increase in the absolute temperature \(T\) implies an increase in \(D\)[10; 11]. In other words, an increase in the pre-deposition and drive-in temperature implies an increase in the diffusion flow density and a potential decrease in the sheet resistance. Figure 2 shows a graph of the carrier lifetime measured using the QSSPC by varying the temperature of the pre-deposition and drive-in processes. The carrier lifetime is a major factor in the fabrication of solar cells because it increases the capability of electron collection, which can be directly related to efficiency. As shown in Figure 2, the carrier lifetime was higher with increasing process temperature because a higher number of carriers could be generated at high process temperatures when the sheet resistance was low due to the high doping concentration of P on the surface and deep inside junction. In addition, when the conditions of the pre-deposition temperature were compared, a higher carrier lifetime (which was an important aspect of solar cell fabrication) of approximately 18 \(\upmu\)s at a minority carrier density of \(5.0\times 10^{15}\) cm\({}^{-3}\) was measured at a low pre-deposition temperature. For the doping process, the drive-in is a process of changing the distribution form of the doping concentration deposited in the pre-deposition step. The concentration at the surface varied with the process temperature. The surface doping concentration and depth of the emitter layer were compared using an SIMS (Secondary-ion mass spectrometry) analysis to measure the profile of the formed emitter layer based on the temperature difference between the pre-deposition and drive-in processes. Figure 1: Surface resistance measurement point and surface resistance in the emitter layer with a temperature difference between the pre-deposition and diffusion processes. Figure 3 shows the SIMS profile of the emitter layer with a difference between the pre-deposition and diffusion processes. After fixing the pre-deposition temperature at 800 \({}^{\circ}\)C, the SIMS profile based on the drive-in process temperature was obtained. As the diffusion coefficient and drive-in process temperatures increased, the surface doping concentration and doping depth increased.