Polycrystalline diamond films produced by Microwave Plasma Enhanced Chemical Vapor Deposition (MWCVD) were investigated for use as dielectric materials for high power and high temperature passive devices. FIlm thicknesses ranged from 0.5 to 100μm and diamond grain sizes were <1 to 30μm depending on thickness. Capacitance and dielectric loss of metal-diamond-metal capacitors were measured as a function of frequency to 10~6Hz, and as a function of temperature from 25 °C to 250 °C. Breakdown strength, resistivity and I-V characteristics were also measured. CVD diamond films that were heat treated to 325 °C for 2hrs., having Si + W + Au contacts, had very steady dielectric constants, ranging from 5 to 6.5, and very low losses, less than 0.005, over 100 to 10~6Hz at room temperature. Dielectric constants of CVD diamond varied by less than 3% with temperature cycling to 250 °C. Losses remained very low (less than 0.01) and stable up to 200 °C. By 250 °C, the dielectric loss had increased to nearly 8X (0.023) its room temperature value (0.003). The effective breakdown strengths of CVD diamond ranged from 2 to 10MV/cm and resistivities ranged from 10~(13) to 10~(15)Ω-cm.
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