Boron Laser Doping through High Quality Al2O3 Passivation Layer for Localized B-BSF PERL Solar Cells

A new doping process is investigated by using Excimer Laser Annealing (ELA) on various Atomic Layer Deposition (ALD)-Al2O3/PECVD-SiNx(B) passivation stack. In a first part the passivation quality of dielectric stacks is investigated on lowly doped p-type Si substrate. Similar passivation level is highlighted with Boron containing SiNx as compared to un-doped SiNx layer when a thin interfacial Al2O3 layer is first deposited on silicon.In a second part laser doping of the silicon substrate is highlighted by sheet resistance (Rsh) decrease. Pulse energy and pulse number influence the diffusion of Boron and Aluminum atoms from the dielectric stack into the silicon. Electro Chemical Voltage (ECV) profiles confirmed p+ region formation. XPS analysis confirmed the presence of both doping atoms in the p+ region. It is suggested that Al is rather bonded to N and O than to Si atoms while B plays a major role in the doping mechanism of the Si lattice.