Self-adaptive Microjet Array Cooling for RF High Power GaN Integration on Silicon

A novel Si interposer with microjet array cooling structure for RF high power GaN integration is presented in this work. The Si interposer is fabricated by stacking 3 wafers to form 2 layers of self-adaptive net microchannels and microjet array. The microfluids converge to form microjets in the bottom layer, then disperse in the top layer in 4 directions at net nodes. The cooling performance of the Si interposer is analyzed using finite element method (FEM) in COMSOL Multiphysics. The analysis results illustrate that the hotspot cooling capacity of the Si interposer depende largely on the flow rate of the coolant. The RF performance and temperature distribution of X-band GaN Monolithic Microwave Integrated Circuit (MMIC) power amplifier (PA) with static power density of ∼ 480 W/cm
²
bonded on the Si interposer were measured in a test cube. The electrical measurement results validate that the cooling performance of the microjet impingement is able to provide the safety operating conditions of GaN MMIC PA. The thermal measurement results demonstrate that the hotspot cooling capacity of the Si interposer enabled GaN PA with hotspot heat density over 323.2 W/mm
²
to operate safely with low flow rate at 70 °C. The interposer is a promising solution for high power integration in silicon-based RF microsystem.