铜基镶嵌结构界面金刚石涂层及其界面热阻的研究

The inlay structure diamond coatings on Cu will be deposited by two steps. The first step comprises the deposition with a electric plating Cu-diamond composite inlay interlayer with a tiny amount of chromium. The diamond particles on inlay interlayer need partially imbed in Cu layer (inlay part) and the remains protrude out of surface (protrude part).In the second step, a continuous diamond coatings which can be used for heat sink application in micro-chips will be deposited by homoepitaxial growth on diamond seeds of protruding out of interlayer with chemical vapor deposition (CVD) method.The thermal boundary resistance of inlay structure diamond coatings on copper substrate can be sufficiently reduced by the co-diffusion of Cu atoms which results of vanishing of the interface between plating Cu and substrate Cu, strengthening the diamond/Cu interface by the inserted layer of Cr3C2 and the enlarged the contact area of inlay structure interface. The interfacial structure and thermal boundary resistance of Cu/Cr3C2, Cr3C2/Diamond and Cu/Cr3C2/Diamond will be studied to determine the coupling mode of thermal transmission particles, ie, electron and phonon.The influence of reducing the Cr3C2 thickness to phonon mean free path scale on thermal boundary resistance will also be investigated for a special increase of interfacial thermal conductance. This program focuses on exploring the method of decreasing thermal boundary resistance, opening out the essential of interfacial thermal resistance and establishing a physical mode to predict thermal boundary resistance of Cu/Cr3C2/diamond and an academic guide of heat sink design of inlay structure diamond coatings on Cu and Cu-diamond composite materials.

在铜基体表面电镀含微量Cr的Cu-Diamond复合镶嵌层，确保金刚石颗粒大部分埋入过渡层中（镶嵌），少部分露出过渡层（露头），以露头为籽晶，在CVD系统中同质外延生长出基于热沉应用的镶嵌结构界面金刚石涂层。电镀Cu与基体Cu界面因高温CVD时Cu原子间的互扩散而消失，Cu/Diamond界面因微量掺Cr而得到强化，Cu/Diamond界面因镶嵌咬合而增大接触面积，这些措施都使界面热阻降低。分别对Cu/Cr3C2,Cr3C2/Diamond和Cu/Cr3C2/Diamond的界面结构和界面热阻进行研究，判断各界面主要热载子耦合方式，并研究Cr3C2厚度在声子平均自由程范围内时对界面热阻的影响。项目致力于探索降低界面热阻的方法，揭示界面热阻的本质，提出预测Cu/Cr3C2/Diamond界面热阻的物理模型,为铜基镶嵌结构界面金刚石涂层热沉和Cu-Diamond复合热沉设计提供理论指导。

制备镶嵌过渡层是沉积出镶嵌结构界面金刚石膜的关键。研究组用不同方法在在Cu或CuCr0.5基体上制备出Cu-diamond镶嵌过渡层，在热丝CVD（Chemical Vapor Deposition）系统中沉积出镶嵌结构界面金刚石膜，并对其界面反应产物，界面结构和膜/基结合性能的影响进行了研究。结果表明，在加固镀液中添加氟硼酸铬，改善了铜与金刚石的界面润湿性能，在CVD系统中沉积出与铜基体结合牢固的金刚石膜。金刚石膜由粗细不等的金刚石颗粒组成，粗颗粒是露头金刚石同质外延长大的，细颗粒是二次形核长大所致。压痕检验结果显示金刚石膜与基体很好。金刚石涂层表面粗糙度大是镶嵌过渡层中露头金刚石露出过渡层的高度参差不齐所致。用模压法将高出过渡层表面的露头金刚石压入包镶过渡层中再进行CVD金刚石膜生长，显著降低了金刚石膜的表面粗糙度，并提高了金刚石膜/基结合性能。研究组采用含铬0.5wt.%的CuCr合金，用油脂+网格均匀化法在CuCr0.5表面分散W40金刚石后，采用模压+去油脂+热模压处理，将W40金刚石颗粒全部压入CuCr0.5中，模压后的Cu-Diamond表面平整，未出现“V”型沟槽和表面裂纹，表面热膨胀系数降低到9.3×10-6/K，可直接用作电子封装热沉和铜基体上CVD沉积金刚石镶嵌过渡层。在CVD金刚石片上分别用磁控溅射法沉积出纳米铜和纳米碳化铬+铜来构建Cu/Diamond和Cu/Cr3C2/Diamond界面，经650℃+2h扩散退火后界面热阻分别为1.73×10-7m2K/W和0.49×10-7m2K/W，显示出用铬改善Cu/Diamond润湿性能并显著降低了界面热阻。本项目研究出铜基嵌入式组合热沉和铜基镶嵌结构界面金刚石涂层是两种全新的热沉，在微电子热沉封装领域具有广阔应用前景。