RF-Sputtered Ti-Based Dielectric Layers as Al-Diffusion Barrier for Passivating Contacts

We investigate TiNx layers deposited via RF magnetron sputtering on their efficacy as a diffusion barrier layer between Al and tunnel oxide passivated contact layer stacks during contact formation in a fast firing process. We obtain implied open-circuit voltage (iVOC) from photo-conductance decay measurements in order to analyse the diffusion barrier quality for different parameter variations. In particular, we show the impact of both higher peak temperature and increased thermal budget (by decreasing the slope of the temperature ramp) on iVoc during the sintering (“fast firing”) process, leading to passivation quality losses. iVOC losses below 1.5% are shown for peak firing temperatures up to 725°C, with absolute values up to 717 mV after firing. Contact formation at this temperature yields median contact resistivity (ρc) values below 3 mΩcm2 with a sheet resistance (Rsheet) of about 40 Ω/□ for the Ti-based layers.