SHF: Small:Thermal Monitoring in 3D Integrated Circuits with Bimetallic Thin Film Thermocouples

集成电路(IC)消耗的电能转化为热量，并通过IC的材料和周围的封装散失。当耗电的高性能芯片垂直堆叠以创建3D IC时，从IC内部到环境的散热变得非常有限。然后，积聚的热量被困在堆叠的IC层之间，这些热量的导热路径很差。因此，IC内部过热威胁到依赖这一重要的新IC设计方法的未来计算系统的安全和性能。该项目将开发一种新的热传感器设计，特别适合在半导体加工步骤中集成到3D IC中。它的设计更小，也就是说，任意数量的传感器可以监控IC中前所未有的部分，并且不会消耗额外的功率。这将影响未来计算系统的可持续性和计算能力，使它们能够在不需要昂贵的主动冷却解决方案的情况下以最高频率运行。它们还会影响芯片产品的定价，从而直接影响到行业和经济。创新进修计划会继续训练研究生和本科生掌握创新科技发展的基础研究，并在社区外展活动中积极推广科学技术。其中一位专业人士还将利用她在她所在机构的多样性委员会的成员资格来吸引代表性不足的少数族裔研究生申请者。该项目涉及一种使用薄膜双金属热电偶(TFBTS)设计热传感器的新范例，它根据与工艺变化和环境热条件无关的固有材料属性来感测温度。由于TFBT是无源的，它们在传感过程中不消耗电力或散热。在更好地理解和建模材料以及将TFBT集成到3D IC方面仍然存在重大挑战。该项目将研究这些热电偶金属随层厚变化的基础科学，因为薄膜的塞贝克系数与块体的塞贝克系数有很大不同。特别是，将进行实验来研究Seebeck系数与薄膜厚度以及热电偶的各种候选金属的选择的关系。在半导体衬底上使用集成电阻加热元件的样品将模拟双金属热电偶阵列下的热点，生成高空间分辨率的热图。将开发有效集成到3D IC中的设计优化。将开发和评估新的热管理方案，这些方案可以利用所产生的细粒度、坚固和低成本的传感器阵列。

Power consumed by integrated circuits (ICs) converts to heat and dissipates through the material of the IC and the surrounding packaging. Heat dissipation from the interior of an IC to the ambient becomes highly constrained when power hungry high performance chips are stacked vertically to create 3D ICs. Pockets of accumulated heat with poor heat conduction paths to the ambient is then trapped in between stacked IC layers. As a result, overheating within ICs threaten the safety and performance of future computing systems that rely on this important new IC design methodology. This project will develop a new thermal sensor design that is especially well suited to be integrated into 3D ICs during semiconductor processing steps. It is smaller by design, i.e., an arbitrarily large number of sensors can monitor an unprecedented part of the IC, and they do not consume additional power. This will impact the sustainability and computational power of future computing systems by enabling them to operate at maximal frequencies without the need for costly active cooling solutions. They also affect the pricing of the chip products and therefore have a direct impact on the industry and economy. The PIs will continue to train graduate and undergraduate students in the basic research that underlies creative technological developments and actively promote science and technology in outreach events to the community. One of the PIs will also leverage her membership in the Diversity Committee at her institution to attract underrepresented minority graduate student applicants. The project involves a new paradigm for design of thermal sensors using Thin Film Bimetallic Thermocouples (TFBTs), which senses temperature according to an intrinsic material property that is independent of process variation and thermal conditions of the environment. Since TFBTs are passive, they do not consume power or dissipate heat during sensing. Significant challenges remain in better understanding and modeling of the materials as well as the integration of the TFBTs into 3D ICs. The project will study the basic science of these thermocouple metals as a function of layer thickness, since thin film Seebeck coefficients are known to differ significantly from bulk. Particularly, experiments will be undertaken to investigate the dependence of the Seebeck coefficient on film thickness and on the choice of various candidate metals for thermocouples. Samples using integrated resistive heater elements on semiconductor substrates will simulate hot spots underneath arrays of bimetallic thermocouples, generating thermal maps with high spatial resolution. Design optimizations for effective integration into 3D ICs will be developed. Novel thermal management schemes that can make use of the resulting fine-grain, robust, and low cost sensor array will be developedand evaluated.