Multilayer Diamond Composites for Heat Spreaders in Electronic Packaging

9522659 Kasichainula该项目解决了高频功率设备对效率更高的散热器的需求。研究方法是利用金刚石的高导热性，通过生长多层复合涂层来防止金刚石层从基材上剥离的常见故障。复合涂层由金刚石、氮化铝或碳化硅层组成。通过热丝化学气相沉积或微波等离子体化学气相沉积在铜、钼或氮化硅衬底上生长出不连续的金刚石微晶层。通过激光物理气相沉积沉积氮化铝或碳化硅层的中间层，金刚石晶体进一步嵌入并锚定到衬底上。在表面光滑的顶部沉积了第二层连续的钻石。在多靶高真空室中，还将通过激光物理气相沉积原位进行金刚石层金属化，沉积薄层钛和阻挡层钨或铬，以防止钛与金锡共晶焊料的相互作用。散热器将使用金-锡或金-硅的共晶合金焊接到器件晶片上，这种合金可以承受高达500K的温度。选择性沉积金刚石多层结构以吸收器件中的热量，最大化接触面积以增加热流密度，以及外延生长金刚石和过渡层以降低复合层中界面的热阻是本研究的重要目标。通过优化金刚石和过渡层的厚度、微观结构和外延生长，使其具有最高的导热系数和良好的附着力。提高对高频热循环产生的应力所产生的失效的抵抗力是该项目的预期优势。为了量化效益，新型和传统散热器的失效机制将通过对它们进行激光脉冲辐射或高功率热球辐射来确定，并通过测量发生剥落的能量密度来量化。垂直于薄膜的有效导热系数将用闪光法测定。使用红外探测装置不同区域的温度，将研究带有新型散热器的电力装置的热冷却模式。多层结构的导热系数和热应力的模拟将分别通过数值求解非线性热方程和有限元分析来进行。随着电子设备尺寸缩小，单位面积存储更多信息，频率增加以加快信息处理速度，局部加热成为一个主要问题。有效冷却这些设备的能力成为进一步发展的技术障碍。随着金刚石涂层技术的出现，出现了利用其高导热系数来散热的机会。然而，金刚石的另一个特性是非粘性，这使得它很难作为附着性涂层来应用。本项目所涉及的这个问题的成功解决可能会对电子行业产生重大影响。

9522659 Kasichainula This project addresses the need for higher efficiency heat spreaders for high frequency power devices. The research approach is to take advantage of high thermal conductivity of diamond by growing a multilayer composite coating to prevent the common failure of delamination of the diamond layer from the substrate. The composite coatings are designed to consist of diamond, aluminum nitride or silicon carbide layers. A discontinuous layer of diamond crystallites is grown on copper or molybdenum or silicon nitride substrates either by hot filament chemical vapor deposition or microwave plasma chemical vapor deposition. The diamond crystallities are further embedded and anchored to the substrate by deposition of an interposing layer of aluminum nitride or silicon carbide layer by laser physical vapor depostion. A second and continuous layer of diamond is deposited on the top with a smooth surface. Metallization of diamond layer with deposition of thin layer of tatanium and a barrier layer of tungsten or chromium to prevent interaction of titanium with the gold-tin eutectic solder will also be carried out in-situ by laser physical vapor deposition in the multi-target high vacuum chamber. The heat spreaders will be soldered to the device wafer using a eutectic alloy of gold-tin or gold-silicon that can withstand temperatures up to 500K. Selective deposition of diamond multilayer structure to absorb heat from the devices, maximization of contact area to increase the heat flux, and epitaxial growth of diamond and interposing layers to reduce the thermal resistance of the interfaces in the composite layers are the important goals of this research. The thickness of the interposing layers, the microstructure and the epitaxial growth of the diamond and the interposing layers will be optimized to give the highest thermal conductivity and good adhesion. Improvement in resistance against failure from stresses generated due to high frequency thermal cycling is the expected bene fit of this project. In an attempt to quantify the benefit, the failure mechanisms of the new and conventional heat spreaders will be determined by subjecting them to laser pulse radiation or high power heat bulb radiation and quantified by measuring the energy density at which peeling takes place. The effective thermal conductivity perpendicular to the film will be determined by the Flash method. Thermal cooling pattern of the power devices with the new heat spreaders will be investigated using the infrared detection of the temperature of different regions of the device. Modeling of the thermal conductivity and thermal stresses in the multilayer structure will be carried out by numerical solution of the non-linear heat equation and finite element analysis, respectively. As electronic devices shrink in size while packing more information per unit area and frequencies increase to speed information processing, local heating becomes a major problem. The ability to effectively cool these devices becomes the technical barrier to further progress. With the advent of diamond coating technology, an opportunity arises to use its high thermal conductivity to dissipate the heat. However, another property of diamond, non-stickiness makes it difficult to apply as an adherent coating. Successful solution of this problem as addressed in this project may have a major impact on the electronics industry.