Performances of CYTOP TM low- k dielectric layer bridged GaAs-based enhancement mode pHEMT for wireless power application

Abstract

Cyclized-perfluoropolymer, which is commercialized under the trade name CYTOP TM, possesses the desirable properties of low dielectric constant ( ε r = 2.1) and low dissipation factor (tan δ = 0.0007). We have developed a method to integrate CYTOP TM dielectric interlayer with state-of-the-art power GaAs-based enhancement mode pseudomorphic high electron mobility transistor. CYTOP TM thin films with approximately 3.5 μm in thickness was spin-coated and patterned on wafers with completed transistor and nitride passivation processes. Au-based interconnect metal was then fabricated using sputtering and plating processes over the CYTOP TM dielectric layer. The whole integrated structure was found to be stable at annealing temperatures up to 200 °C. Moreover, output power, gain, and power added efficiency of the CYTOP TM-integrated 0.5 μm gate transistor was measured and compared with standard air-bridged devices. The studies show that the CYTOP TM low- k dielectric layer has negligible effect on the device performances as compared with the air-bridged devices.