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

Cyclized-perfluoropolymer, which is commercialized under the trade name CYTOPTM, possesses the desirable properties of low dielectric constant (er = 2.1) and low dissipation factor (tan δ = 0.0007). We have developed a method to integrate CYTOPTM dielectric interlayer with state-of-the-art power GaAs-based enhancement mode pseudomorphic high electron mobility transistor. CYTOPTM 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 CYTOPTM 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 CYTOPTM-integrated 0.5 μm gate transistor was measured and compared with standard air-bridged devices. The studies show that the CYTOPTM low-k dielectric layer has negligible effect on the device performances as compared with the air-bridged devices.