Contact resistance to SrRuO₃ and La_0.67Sr_0.33MnO₃ epitaxial films

Contact resistance to the metallic oxide electrodes, SrRuO₃ (SRO) and La_0.67Sr_0.33MnO₃ (LSMO), is an important parameter that affects the ferroelectric tunnel junction (FTJ) device performance. We have systematically studied the contact resistance between metallic oxide electrodes (SRO, LSMO) and contact metal overlayers (Ti, Pt) after exposure to various processing environments. Specific contact resistivity (ρ_c) for Ti and Pt contact metals and the sheet resistance (R_sh) of the metallic oxides are measured after exposure to different reactive ion plasma process steps. Sheet resistance degradation was observed for both SRO and LSMO films after exposure to plasma treatment. Severe contact resistance degradation was observed for Ti contacts as compared to Pt after reactive ion etching on LSMO films. The effect of oxygen (O₂) plasma on LSMO was observed to be most severe with non-ohmic behavior with Ti contacts, which can affect the functionality of FTJ devices. Finally, the thermal stability of contacts was investigated, Pt contacts to SRO show low resistance ohmic behavior even after annealing at 900 °C, making it a suitable contact for FTJ devices.