Multilayer Diamond Composites for Heat Spreaders in Electronic Packaging

小行星9522659 该项目解决了高频功率器件对更高效率散热器的需求。 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与基体分层的常见失效。 复合涂层被设计成由金刚石、氮化铝或碳化硅层组成。 通过热灯丝化学气相沉积或微波等离子体化学气相沉积在铜或钼或氮化硅衬底上生长金刚石微晶的不连续层。 通过激光物理气相沉积沉积氮化铝或碳化硅层的插入层，金刚石晶体被进一步嵌入并锚定到基底上。 第二层和连续的金刚石层沉积在具有光滑表面的顶部上。 金刚石层的金属化，同时沉积一薄层钛和一层钨或铬的阻挡层，以防止钛与金锡共晶焊料的相互作用，也将在多靶高真空室中通过激光物理气相沉积原位进行。 散热器将使用金锡或金硅的共晶合金焊接到器件晶片上，该合金可以承受高达500 K的温度。 选择性沉积金刚石多层结构以吸收器件的热量，最大化接触面积以增加热通量，以及外延生长金刚石和插入层以降低复合层中界面的热阻是本研究的重要目标。 将优化插入层的厚度、金刚石和插入层的微结构和外延生长，以提供最高的热导率和良好的粘附性。 提高对由于高频热循环产生的应力的抵抗能力是该项目的贝内。 在量化益处的尝试中，将通过使新的和传统的散热器经受激光脉冲辐射或高功率热灯泡辐射来确定它们的失效机制，并且通过测量发生剥离的能量密度来量化。 垂直于薄膜的有效导热率将通过Flash方法测定。 采用红外线检测器件不同区域的温度，研究具有新型散热器的功率器件的热冷却模式。 多层结构中的导热系数和热应力的建模将分别通过非线性热方程的数值解和有限元分析来进行。 随着电子设备的尺寸缩小，同时每单位面积上封装更多的信息，以及频率增加以加快信息处理，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，利用其高导热性来散热的机会出现了。 然而，金刚石的另一个特性，非粘性使得它难以作为粘附涂层应用。 成功解决这个问题，在这个项目中解决可能会对电子工业产生重大影响。

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.