Integrated Terahertz Measurement Systems based on Heterogeneously Integrated Sensors

电磁频谱的太赫兹（或亚毫米波）区域长期以来一直被认为对于射电天文学、大气物理学和遥感等领域的基础科学探究和进步至关重要。此外，新兴的设备概念有望为进一步的科学研究以及成像、无损测试和评估以及高带宽通信方面的重要应用打开这个基本上难以访问的频谱。不幸的是，开发这些新技术所需的基础设施和测量工具仍然严重有限。当前实现亚毫米波长测量仪器的方法主要基于使用波导接口的模块化方法。这导致完全组装的测量设备具有相当大的几何足迹，这可能被证明笨重或不适合许多重要场景，例如当待测试的设备或系统必须维护在屏蔽外壳（例如真空室或低温恒温器）内的情况下。该项目的重点是通过开发紧凑且薄型的测量仪器来解决这一关键问题，这些测量仪器基于与微机械支撑膜异构集成的高性能太赫兹传感器，允许在太赫兹频率下对平面器件和系统进行直接接触原位表征。因此，这项工作将通过提供新的和先进的计量仪器来对不断发展的太赫兹研究界产生广泛的影响，这些仪器允许目前不可能或不可行的测量。新测量技术和能力的创造是科学进步的基础；科学发现和工程进步取决于仪器的创造，这些仪器为实验和探究开辟了新的物理领域。 这项工作代表了开发仪器的最初、关键和必要的一步，这些仪器克服了限制当前太赫兹计量方法的固有缺陷。该项目的目标和范围是通过开发基于异构集成的仪器技术来推进太赫兹设备、组件和系统的测量和表征的基础设施。所从事的研究重点是跨材料系统（例如，III-V 半导体和硅）和跨物理领域（例如，电子和机械）的异构集成。为此，要采取的具体方法包括三个主要重点：（1）开发异质集成到薄硅膜上的低寄生太赫兹肖特基二极管传感器的处理技术，（2）研究和实现结合集成肖特基传感器的基于硅膜的微机械晶圆探针，以及（3）研究和原型设计紧凑的高阶太赫兹倍频器源，以便与基于异质集成的测试和测量仪器集成。 研究实现这种集成的工艺具有内在的智力价值，并且该提案的大量工作致力于研究允许制造高性能太赫兹电子传感器的方法，该传感器具有机械坚固的主基板，适合直接的物理接触界面，而无需固定。这项工作将解决太赫兹器件设计、制造技术和计量学的基本问题，目的是实现目前不可能或不可行的测量的新型先进仪器。

The terahertz (or submillimeter-wave) region of the electromagnetic spectrum has long been understood as crucial to fundamental scientific inquiry and progress in fields such as radio astronomy, atmospheric physics, and remote sensing. Moreover, new and emerging device concepts promise to open this largely-inaccessible spectrum to further scientific study as well as important applications in imaging, non-destructive test and evaluation, and high-bandwidth communications. Unfortunately, the infrastructure and measurement tools needed to develop these new technologies remain severely limited. Current approaches to realizing measurement instrumentation at submillimeter wavelengths are based largely on a modular approach using waveguide interfaces. This results in fully-assembled measurement apparatus with considerable geometric footprint that can prove unwieldy or unsuitable for many important scenarios, for example in situations when the device or system to test must be maintained within a shielded enclosure such as a vacuum chamber or cryostat. This project is focused on addressing this critical issue through the development of compact and low-profile measurement instruments that are based on high-performance terahertz sensors heterogeneously integrated with micromachined support membranes that allow direct-contact in situ characterization of planar devices and systems at terahertz frequencies. As a consequence, this work will have broad impact on the growing terahertz research community through the availability of new and advanced metrological instrumentation that permit measurements that presently are not possible or feasible. The creation of new measurement techniques and capabilities is fundamental to the advancement of science; scientific discovery and progress in engineering are predicated on the creation of instruments that open new physical domains for experimentation and inquiry. This work represents an initial, critical, and necessary step towards developing instruments that overcome the inherent drawbacks limiting current approaches to terahertz metrology.The goal and scope of this project is to advance the infrastructure for measurement and characterization of terahertz devices, components, and systems through the development of instrumentation technologies that are based on heterogeneous integration. The research pursued focuses on heterogeneous integration across materials systems (e.g., III-V semiconductors and silicon) and across physical domains (e.g., electronics and mechanics). Towards this end, the specific approach to be undertaken includes three primary thrusts: (1) development of processing technologies for low-parasitic terahertz Schottky diode sensors heterogeneously integrated onto thin silicon membranes, (2) investigation and implementation of silicon membrane-based micromachined on-wafer probes incorporating integrated Schottky sensors, and (3) research and prototyping of compact, high-order terahertz frequency multiplier sources for integration with test and measurement instrumentation based on heterogeneous integration. There is inherent intellectual merit in researching processes that enable such integration and a significant effort of this proposal is dedicated to investigating methods that permit fabrication of high-performance terahertz electronic sensors with mechanically-robust host substrates amenable to direct, physical contact interfaces without need for fixturing. Fundamental issues of terahertz device design, fabrication technology, and metrology will be addressed during this work with the aim of realizing new and advanced instrumentation that permit measurements that presently are not possible or feasible.