Fabrication and characterization of integrated micro-thermoelectric coolers usingchemical and physical vapor deposition

微型热电制冷器(µTEC)旨在为产生热量或需要准时精确控制温度的电子元件提供局部冷却。µTECs的一个很有前途的潜在应用是光电子元件的局部温度控制。激光器，特别是用于数据传输的激光器，需要极其精确的温度控制。如果激光腔暴露在温度波动中，其几何尺寸会因热膨胀而变化，从而立即降低数据传输的效率。今天，通常情况下，整个宏观组装是主动冷却的。一个额外的加热器被放置在靠近光电组件的位置，以实现所需的精确温度稳定。通过将当今的技术解决方案替换为直接在光电子元件上使用集成微TEC的温度稳定，可以在降低成本的情况下提高数据传输的总效率。微TECs中最先进的热电材料是通过电镀方法生产的，因为这符合CMOS(互补金属氧化物半导体)后端技术的要求，但存在热电转换效率较低的问题。然而，由于材料的质量较差，因此不能实现用于目标应用的冷却功率，并且将要求具有显著更高的转换效率的热电材料。因此，对于在仍完全兼容CMOS后端的技术中提供显著提高转换效率的热电材料的技术解决方案有着明显的需求。热电材料的最高允许加工温度为200°C，这对合成方法是一个挑战。虽然电镀方法与这种温度范围相兼容，但所获得的材料的质量是不够的。本项目还将研究另外两种沉积技术：化学气相沉积(CVD)和物理气相沉积(PVD)。对于化学气相沉积，将通过使用不耐热的金属有机前体和特殊的单源前体相结合来实现较低的衬底温度，这些前体包含已经在分子水平上的材料的构建单元。同样的策略将应用于PVD，选择处理温度，使前体有足够的蒸汽压。这两种方法的原则上的可行性可以在两个申请者团队的初步工作中得到证实。但现在需要对基本机制进行基础和系统的研究，以便成功地将这两种合成方法应用到器件制造中。这将通过本项目申请来实现。

Micro-thermoelectric coolers (µTECs) are intended to provide cooling locally at the electronic component where heat is produced or a punctual and precise control of the temperature is necessary. A promising potential application of µTECs is the local temperature control of optoelectronic components. Laser, especially for data transmission, require an extremely precise temperature control. If the laser cavity is exposed to temperature fluctuations, its geometrical dimensions vary due to thermal expansion, immediately reducing the efficiency of the data transmission. Today, typically the complete macroscopic assembly is actively cooled. An additional heater is placed close to the optoelectronic component for the required precise temperature stabilization. The total efficiency of the data transmission could be improved at reduced costs by the substitution of today’s technological solution by a temperature stabilization using integrated µTECs directly at the optoelectronic component. The state-of-the-art thermoelectric material in µTECs is produced by an electrochemical plating method since this is compatible with the requirements of a CMOS (complementary metal oxide semiconductor) back-end technology, but suffers from its poor thermoelectric conversion efficiency. However, the cooling power for the target-application can hereby not be realized due to the poor material’s quality, and thermoelectric material with a noticeably higher conversion efficiency would be requested. Therefore, there is a clear demand for technological solutions providing thermoelectric material with significantly increased conversion efficiency within a technology that is still fully compatible with CMOS back-end.The maximum allowed processing temperatures for the thermoelectric material is 200 °C, which is a challenge for the synthetic approach. While electrochemical plating methods are compatible with this temperature regime, the quality of the obtained material is not sufficient. There are two other deposition techniques that will be studied within this project: Chemical vapor deposition (CVD) and physical vapor deposition (PVD). For the CVD, the low substrate temperatures will be achieved by the use of thermolabile metalorganic precursors combined with special single-source-precursors that contain the building units of the material already at the molecular level. The same strategy will be applied for PVD, chosing processing temperatures such that a sufficient vapor pressure of the precursors is given.The principle feasibility of both approaches could be substantiated within preliminary work of the two applicants’ teams. But fundamental and systematic studies of the underlying mechanisms is now requested to allow for successful implementation of these two synthetic approaches into devices fabrication. This shall be realized by this project application.