Dry Chemical Etching of Gallium Arsenide in OMVPE Reactors

金属有机气相外延(OMVPE)外延生长砷化镓(GaAs)已被用于生长各种III-V和II-VI化合物半导体以及用于电子和光电子器件。通过气体流动可视化和数值模拟等手段对OMVPE生长的反应器设计进行了优化。与分子束外延(MBE)相比，OMVPE的一个主要优点是其生长速度可以比MBE高四到十倍，从而使大规模生产电子器件成为可能。如果能够实现完整的器件原位加工，如刻蚀、图案化和再生长，可以提高OMVPE在大规模器件制造中的产量和成品率。这种工艺的优点是：(1)有可能制造低损耗埋入波导和低阈值埋入二极管激光器(2)简化工艺(3)低污染因此，PI正在开发具有原位能力的简单干法蚀刻工艺的接口，大面积刻蚀，无污染物引入或表面退化。在这项研究中，他们计划研究使用甲基自由基源的原位干法化学刻蚀GaAs和AlGaAs。PI计划在OMVPE生长中典型的接近大气压的情况下，使用几种甲基自由基源研究砷化镓的“反向生长”或“刻蚀”。这些研究将确定最有希望的源和操作条件，在没有杂质积聚和/或表面形态变化的情况下，在OMPVE反应器中原位刻蚀GaAs。偶氮甲烷、碘甲烷、碘化氢和三甲基砷将在300-600摄氏度的温度范围内作为源化合物进行检查。另一个目标是研究刻蚀的取向相关性。将研究暴露出不同晶体取向的图案化基板。刻蚀的各向异性也将用掩膜衬底进行检查。此外，这项工作的目的是确定条件和理解导致“糟糕的”刻蚀制度的过程，无论是衬底形态的变化还是杂质的加入都证明了这一点。

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.