Research of Annealing and Boron Doping on SiOx/p+-Poly-Si Hole-Selective Passivated Contact

Advanced contact structures typically feature both low contact resistance ρ _c and low recombination current densities J ₀ . Carrier-selective passivated contact is a widely adopted approach. Electron-selective passivated contact structures based on SiO _x /n ⁺ -poly-Si have been extensively studied. Excellent passivation quality with J ₀ down to 1 fA/cm ² and low contact resistivity less than 1 mΩ·cm ² were reported. However, hole-selective passivated contact based on SiO _x /p ⁺ -poly-Si still lacks extensive research, and it is not yet proven by a mass production-available metallization method. In this article, we investigated the effects of different annealing condition on the passivation performance of SiO _x /p ⁺ -poly-Si, and carefully adjusted the doping profile to study the effect of doping profile on passivation and contact resistivity based on the screen printing metallization scheme. The results indicated that the SiN _x was helpful for passivation and the subsequent annealing condition was also very important for achieving excellent surface passivation. In addition, the high boron doping concentration in poly-Si while shallowly penetrating through the tunnel oxide into the silicon bulk was essential for obtaining low J ₀ and ρ _c . A minimum J ₀ of 5 fA/cm ² and ρ _c of 1.5 mΩ·cm ² have been achieved separately in this work. The slight penetration of the boron atoms into the oxide layer slightly reduces ρ _c , but the penetration needs to be controlled to reach an optimum combination of J ₀ and ρ _c . Through the optimization of the boron dopant profiles, a combination of J ₀ of 5.5 fA/cm ² and ρ _c of 9-mΩ·cm ² was obtained.