Multilayer capacitors in polycrystalline diamond by rapid thermal annealing

Polycrystalline diamond (PCD) can be grown over a range of thicknesses from 2 μm to over 200 μm by a variety of techniques. The PCD films can be obtained with very high resistivities exceeding 10 ¹¹ Ω-cm or they can be doped with boron to produce high resistance conductors. Metal bonds to polycrystalline diamond (PCD) are important for the realization of ohmic contacts for electronic devices and the adhesion of PCD films to various materials in the fabrication of PCD-based sensors and actuators. We have investigated the formation of titanium contacts on PCD and aluminum silicide bonding of the PCD films to a variety of substrates by rapid thermal techniques. All high temperature process times were kept to 2.5 minutes and only the maximum temperature was varied for optimum results in each sintering step. Two alternative rapid thermal processing systems were used: (a) a cylindrical cavity system with a narrow area coverage for the formation of titanium carbide and titanium silicide bonds, and (b) a rectangular cavity system with large area coverage for the formation of aluminum silicide bonds. The cylindrical cavity system was capable of achieving higher temperatures and was, therefore, used for the formation of the Ti/PCD and Ti/Si contacts. Optimum sintering temperatures were found to be: 885±15°C for Ti/PCD contacts, 710±5°C for Ti/Si and 650°C for Al/Si for 36 μm thick aluminum foil. Argon gas was used for the ambient in all sintering operations