基于金刚石散热片的 GaN 器件热压键合研究

近年来，GaN 射频器件在高频应用场景大放异彩，但 GaN 射频器件的 高功率带来的高工作结温问题反而限制了其优点的发挥，解决 GaN 射频器件散热问题是进一步扩展其应用的必经之路。而金刚石拥有优异的热导性， 利用金刚石辅助 GaN 射频器件散热的重点在于将器件有源面上的高工作结温通过键合层扩散至散热片。本文提出利用金等金属作为键合层材料，辅助 GaN 射频器件将热扩散至散热片。

通过使用拥有高导热性能的纯金材料，将 GaN 射频器件与金刚石键合起来，可以有效地改善器件工作时高热量密度的情况，提升器件的可靠性，延长器件的使用寿命。本文主要完成的工作如下：

在进行键合工艺实验阶段，使用硅片代替硅基 GaN 外延片及金刚石片，对其表面进行金属化后完成热压键合。探究了在相同的键合温度、键合时间的条件下，改变键合压力和键合层厚度对于键合质量的影响，并研究了各参数样品整体热传导性能，性能测试后取热传导性能最佳的工艺参数完 成硅基 GaN 外延片及金刚石薄片的热压键合，所得样品键合情况良好。

使用原子力显微镜、扫描电子显微镜、能谱仪、超声扫描显微镜及热常数分析仪从多角度分析了样品的键合质量，发现当金层厚度为 300 nm、 键合压力为 9 MPa、键合温度为 300℃、键合时间为 60 min 所得样品键合层综合效果最好，键合率为 97%，热导率为 101.32 W/(mK)，热扩散率为 44.45 mm²/s。

In the latest developments, GaN RF PA devices have exhibited remarkable efficacy in high-frequency applications. However, the high power of GaN RF PA devices results in a high working temperature that limits their full potential. Therefore, resolving the heat dissipation issue is crucial to further expand the application of GaN RF PA devices. Diamond, renowned for its excellent thermal conductivity, offers a promising solution to this challenge. The key to utilizing diamond as a heat spreader to aid GaN power device heat dissipation is to diffuse the concentrated high working temperature on the active surface of the GaN power device to the heat spreader through a bonding layer. This study proposes employing gold as the bonding layer material to assist GaN RF PA devices in dissipating heat to the heat spreader.

By utilizing high thermal conductivity gold, it is possible to bond GaN RF devices with diamond, thus significantly enhancing their high heat density, improving their reliability, and extending their lifespan. The main objective of this research is as follows:

(1) At the bonding process experiment stage, silicon wafers are utilized to substitute silicon GaN epitaxial wafers and diamond wafers, with their surfaces metallized to perform thermal compression bonding. By changing the bonding pressure and bonding layer thickness while maintaining the same bonding temperature and bonding time, the influence of these variables on the bonding quality is explored, and the overall thermal conductivity of each parameter of the sample is studied. After conducting performance tests, the process parameters with the highest heat conductivity are chosen for the thermal compression bonding of silicon GaN epitaxial sheet and diamond sheet, resulting in well-bonded samples.

(2) The bonding quality of the samples is then analyzed using atomic force microscope, scanning electron microscope, energy spectrometer, ultrasonic scanning microscope and thermal constant analyzer. The composite effect of the bonding layer is found to be optimal when the thickness of the gold layer is 300 nm, the bonding pressure is 9 MPa, the bonding temperature is 300℃, and the bonding time is 60 min. The bonding rate is 97%, with a thermal conductivity of 101.32 W/(mK) and a thermal diffusivity of 44.45 mm² /s.

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