Microfluidic silicon interposer for thermal management of GaN device integration

Abstract

With the popularity of the third generation semiconductor applications, silicon-based hetero-integration is driven to be applied massively by the miniaturization of microsystems and modules. The system-level power has a sharp increase in recent years, and consequently, hotspot thermal management is being increasingly concerned. A high-power GaN device with chip heat fluxes > 500 W/cm2 and hotspot heat fluxes > 30 kW/cm2 is implemented in this work to study extremely uneven hotspot cooling for silicon-based hetero-integration. A customized microjet silicon interposer (SI) is designed and fabricated based on the on-chip hotspot distribution, and another common microchannel SI in similar sizes is prepared for comparison. The GaN device is integrated on SI and micro-assembled in a test cube. The measurement results demonstrate that the maximum junction temperature of the GaN device on microjet SI is down to 150.3 ℃ at 70 ℃ ambient temperature with a pressure drop of 231.9 kPa. The overall thermal resistance (TR) of the test vehicle with microjet cooling has a 7.11 ∼ 7.72 % reduction and its heat transfer coefficient (HTC) increases by 12.3 ∼ 28.3 % compared to that with microchannel cooling with the pumping power of 0.5 ∼ 1.5 W. The material properties of the GaN chip and SI are extracted from the measurement results and then used in the analysis of the thermal and hydraulic properties of both microfluidic SIs numerically. Their cooling performance and efficiency are evaluated and compared based on the performance evaluation criteria (PEC), field synergy number and entropy generation rate. According to the evaluation results, while the PEC of microjet and microchannel SIs increases with the pumping power, the microjet SI can contribute to the enhancement of the synergetic relationship between the flow and temperature fields and reduction of total irreversibility in the heat transfer process compared to the microchannel SI in pursuit of low overall TR. The field synergy number improves by 90.40 % and the argument entropy generation rate is 0.376 when the overall TR is 1.35 K/W. The findings can provide valuable references for hotspot thermal management in silicon-based hetero-integration.