Ohmic contacts on diamond were fabricated using a Ti/Pt/Au metallization scheme and two transmission line model masks. The double mask system is used to isolate the Ti by surrounding it with Pt. Pt is expected to prevent Ti diffusion either to the contact surface or along the diamond surface during annealing. In this study we found that this system of masks was successful in preventing the Ti diffusion as revealed by Auger analysis on the diamond and contact surfaces. An Auger depth profile revealed that the Ti was confined to the diamond/contact interfacial region, and was most likely combined with Pt.