Hydrogen Stability and Bonding in SiN _x and Al₂O₃ Dielectric Stacks on Poly-Si/SiO _x Passivating Contacts

Polycrystalline Si on SiO x passivatingcontacts enables some of the highest efficiency single-junction Siphotovoltaic devices, but the high-temperature firing process neededfor industrial metallization can significantly reduce passivation.We show that after firing, the implied open-circuit voltage, iV (oc), for the Al2O3/SiN x /poly-Si/SiO x /c-Si stack is 20-30 mV higher than the SiN x /Al2O3/poly-Si/SiO x /c-Si stack and therefore provides better passivation of theSiO( x )/c-Si interface. Using effusion measurementsand Fourier transform infrared spectroscopy, we demonstrate that morethan twice as much hydrogen is retained in the dielectric up to thepeak firing temperature of & SIM;800 & DEG;C for Al2O3-capped structures. If the Al2O3 layeris not present in the stack, after firing, the iV (oc) is lower by 50-100 mV compared to Al2O3/SiN x or SiN x /Al2O3 stacks. These studieswill inform future work on the role of dielectrics in aiding the passivationof poly-Si/SiO x passivating contacts.