Dry Chemical Etching of Gallium Arsenide in OMVPE Reactors

砷化镓（GaAs）的有机金属气相外延（OMVPE）外延生长已被用于生长各种III-V和II-VI化合物半导体以及电子和光电子器件。通过气体流动可视化和数值模拟等方法对OMVPE生长反应器进行了优化设计。与分子束外延（MBE）相比，OMVPE的一个主要优势是前者的生长速度可以比MBE高4到10倍，这使得电子器件的大规模生产成为可能。如果完整的原位器件加工，如蚀刻，图像化和再生，可以提高OMVPE在大规模器件制造中的吞吐量和良率。这种处理的优点是：(1)制造低损耗埋地波导和低阈值埋地二极管激光器的潜力(2)简化处理(3)低污染因此，pi正在开发一种简单的干蚀刻工艺，具有原位，大面积蚀刻，无污染物引入或表面降解。在这项研究中，他们计划研究甲基自由基源对GaAs和AlGaAs的原位干化学蚀刻。pi计划在OMVPE生长的典型大气压下，使用几种甲基自由基源研究GaAs的“反向生长”或“蚀刻”。这些研究将确定最有希望在OMPVE反应器中原位蚀刻GaAs的来源和操作条件，而不会产生杂质积聚和/或表面形貌变化。在300-600℃的温度范围内，偶氮甲烷、碘甲烷、碘化氢和三甲基砷将作为源化合物进行检查。另一个目的是研究蚀刻的取向依赖性。本文将研究不同晶体取向的图案化衬底。用掩膜衬底考察刻蚀的各向异性。此外，这项工作旨在确定导致“不良”蚀刻制度的条件和理解过程，这可以通过衬底形态变化或杂质的掺入来证明。

The epitaxial growth of gallium arsenide (GaAs) by organometallic vapor phase epitaxy (OMVPE) has been used to grow various III-V and II-VI compound semiconductors and for electronic and optoelectronic devices. Optimizing the reactor design for OMVPE growth has been done by, for example gas flow visualization and numerical simulation. A major advantage of OMVPE over molecular beam epitaxy (MBE) is that the growth rates of the former can be four to ten times higher than MBE, making feasible the production of electronic devices on a large volume scale. The OMVPE throughput and yield in large- scale device fabrication could be enhanced if complete in-situ device processing, such as etching, patterning and regrowth were demonstrated. The advantage of such processing are: (1) potential for fabrication of low-loss buried waveguides and low threshold buried diode lasers (2) simplified processing (3) low contamination The PIs are therefore working at interfaces developing a simple dry etching process with capabilities for in-situ, large area etching without contaminant introduction or surface degradation. In this study, they plan to investigate the in-situ dry chemical etching of GaAs and AlGaAs using methyl radical sources. The PIs plan to study the "reverse growth" or "etching" of GaAs using several methyl radical-sources at near atmospheric pressure typical in OMVPE growth. These studies will identify the most promising source and operating conditions for the in-situ etching of GaAs in OMPVE reactors without impurity buildup and/or surface morphology changes. Azomethane, iodomethane, hydrogen iodide, and trimethyl arsenic will be examined as source compounds at temperatures in the range of 300-600oC. Another objective is to examine the orientation dependence of etching. Patterned substrate with different crystal orientations exposed will be studied. The anisotrophy of etching will also be examined with masked substrate. Additionally, the work aims at identifying the conditions and understanding the process leading to "poor" etching regimes as evidenced by either substrate morphology changes or the incorporation of impurities.