Improved Ti/Pt/Au - n-Type Si Contacts by Post-Metallization Annealing in Nitrogen Atmosphere

Abstract

A metallic sandwich (Ti/Pt/Au) is deposited on n-type Si and subsequently subjected to post-metallization annealing at temperatures ranging from 500°C to 950°C, with a step of 50°C. XRD microstructural investigations evince the effect of post-metallization annealing, focusing on the formation of the silicide interface layer at each of the annealing temperatures. The electrical quality of the contacts was analyzed based on the linear transfer length method using test structures with different gaps between the pads. Accordingly, the sheet resistance, the contact resistance, the transfer length and the specific contact resistivity are determined. It is demonstrated that sheet resistance improves with more than three orders of magnitude at 900°C, compared the reference sample. The contact resistance also improves with more than one order of magnitude, reaching a minimum value of 1.68Ω at 950°C. The transfer length reaches a maximum value of 10.8 μm at 750°C, corresponding to a specific contact resistivity of 4.82.10-5Ω· cm2. Finally, an effective resistivity for the fabricated ohmic contact of 0.033 Ωcm is obtained for PMA at 950°C.