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This article reports a high throughput 150-nm-gate AlGaN/GaN high electron mobility transistor (HEMT) process using i-line stepper lithography and a thermal reflow technique. Optimizing thermal reflow conditions, fabrication of a 150-nm gate structure was successfully realized with the initial resist opening of 0.7 μm. AlGaN/GaN fieldplated HEMTs were fabricated on a semi-insulating SiC substrate by using this process. In spite of unoptimized structures, fabricated 150nm gate devices exhibited the maximum drain current of 0.65 A/mm and the gate-drain breakdown voltage exceeding 200 V. Based on cold HEMT extraction measurements, the average gate length of 187 nm and the standard deviation of 30 nm were obtained on a quarter 4-in. wafer.

This article reports radio frequency characteristics of 150-nm gate aluminum gallium nitride (AlGaN)/gallium nitride (GaN) high electron mobility transistors (HEMTs) fabricated using i-line stepper lithography and a thermal reflow technique. The authors have developed two different gate structures that were a field-plated gate using the lift-off process and a Y-shaped gate using the ion-milling process. Fabricated HEMTs using these different gate structures exhibited nearly equivalent DC characteristics. The field-plated gate device showed a unity current gain cutoff frequency (f T ) of 35 GHz and a maximum oscillation frequency (f max ) of 106 GHz, while the Y-shaped gate device showed f T of 36 GHz and f max of 115 GHz. The equivalent circuit analysis indicated a decrease in the gate-drain capacitance and the drain conductance is responsible for the improved f max in the Y-shaped gate device.