SBIR Phase II: In-Situ, Real-Time Process Control for Micro-Electro-Mechanical System (MEMS) Applications

这个小型企业创新研究第二阶段项目将开发一种用于微电子机械系统(MEMS)深蚀刻制造的多应用、低成本、实时过程监控工具。深蚀刻工艺被用于制造厚达数百微米的高宽高比结构，并有望以更低的成本提供性能和功能更高的新器件。深刻蚀技术的一个主要困难是对刻蚀深度的控制，目前采用非原位破坏性扫描电子显微镜测量刻蚀后的刻蚀深度。这是极其低效的，而且是在大规模生产之前需要克服的主要障碍。在第一阶段，基于FTIR的传感器被设计、建造并安装在蚀刻室的顶部。首次在几种MEMS结构上进行了原位和实时的刻蚀深度和光刻胶厚度测量。FTIR测量结果与扫描电子显微镜测量结果之间具有很好的相关性。在第二阶段，将开发和实施分析模型，以测量尽可能广泛的MEMS结构。这些模型将在任何类型的图案上提取多个参数，并将允许传感器用于各种应用，包括硅或SOI(绝缘体上硅)晶片中的深槽、薄膜、厚光刻胶，以及主流硅应用，如DRAM(动态随机存取存储器)槽。硬件将针对光斑大小、测量光斑范围、紧凑性进行优化，对于对成本敏感的MEMS行业来说，更重要的是针对成本进行优化。该项目的结果将是开发一种计量工具，该工具目前没有能力，而且需求很高，而且还在不断增加。使用所提出的计量方法的具体预期结果是：(1)通过减少破坏性测量和改进工艺控制来降低成本，(2)通过更好的工艺控制来提高MEMS结构的重现性(运行到运行的精度目前为~3%，使用传感器预计将降低到0.5%)，(3)为工艺开发提供有用的反馈，从而缩短开发时间。这些结果将对深蚀刻MEMS市场产生重大影响，因为它们将通过更便宜的表征和改进的工艺控制，帮助未来的MEMS应用成熟并更快地进入市场。此外，这种首创的实时晶圆状态监测和控制技术将在DRAM等主流半导体工艺中得到应用。

This Small Business Innovation Research Phase II project will develop a multiple-applications, low-cost, real-time process monitoring and control tool for micro-electro-mechanical system (MEMS) deep-etch fabrication. Deep-etch processes are used to manufacture high aspect ratio structures up to several hundred microns thick, and promise to deliver new devices with increased performance and functionality at lower cost. A major difficulty in deep-etch technology is the control of the etch depth, which is currently measured post-etch using ex-situ destructive scanning electron microscopy. This is extremely inefficient, and is a major hurdle to be surmounted before extensive production takes place. During Phase I, an FTIR-based sensor was designed, constructed and installed on top of an etcher chamber. Etch depth and photoresist thickness measurements were obtained, for the first time ever, in-situ and in real-time on several MEMS structures. An excellent correlation between the FTIR measurements and SEM measurements was found. During Phase II, analysis models will be developed and implemented to measure the widest possible range of MEMS structures. These models will extract multiple parameters on any type of patterns, and will allow the use of the sensor for various applications, including deep trenches in silicon or SOI (silicon on insulator) wafers, membranes, thick photoresist, and mainstream silicon applications such as DRAM(Dynamic Random Access Memory) trenches. Hardware will be optimized for spot size, measurement spot range, compactness and, very importantly for the cost-sensitive MEMS industry, for cost. The result of this project will be the development of a metrology tool with capabilities currently unavailable, and which are in high and increasing need. The specific anticipated results of the use of the proposed metrology are: (1) to reduce cost through the reduction of destructive measurements and the improvement in process control,(2) to increase the reproducibility of the MEMS structures through better process control (run to run accuracy is currently ~3 % and is expected to be lowered by the use of the sensor to 0.5 %), (3) to provide useful feed-back for process development, thus reducing development time. These results will have a great impact on the deep-etch MEMS market, as they willhelp future MEMS applications to mature and come to market at a faster pace through cheaper characterization and improved process control. In addition, this first-of-a-kind real-time wafer-state monitoring and control technology will lead to applications within mainstream semiconductor processing such as DRAM.