Ultra-thin LPCVD SiNx/n+poly-Si passivated contacts – A possibility?

This work explores the possibility of using ultrathin silicon nitride (SiN x ) films with high positive fixed charge in a SiN x /poly-Si passivating contact. The factors including (i) film thickness, (ii) annealing condition (time, temp and ambient) and (iii) surface pre-treatment were optimized to boost the passivation performance of ultrathin LPCVD SiN x films. Our preliminary experiments reveal excellent surface passivation and low recombination current density, J o (45 fA.cm-2) by ~1.5 nm thick LPCVD SiN x films when subjected to an air ambient anneal at 800°C for 30 mins. This is due to the formation of high positive fixed charge density (1.5 ×10 12 cm-2). Air ambient annealed (465 μs) samples also have a higher lifetime when compared to the forming gas annealed (208 μs) samples. These passivating SiN x films were further integrated into SiN x /n+poly-Si contacts and characterized for J o,contact and tunneling resistance, ρ contact . The best SiN x /n+poly-Si passivated contact in this study has J o, contact = 5.9 fA.cm-2, ρ contact = 0.525 Ω.cm2 and an efficiency potential > 22.75%. According to our knowledge, it is the first report confirming the formation of passivated contacts with SiN x as the dielectric tunnel layer.