Fabrication of micro and nanophotonic devices
Date
2011
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Publisher
University of Delaware
Abstract
As the interconnect bottleneck in electronic circuits is becoming a more serious problem, optical (or photonic) interconnects are becoming a promising solution. Optical interconnects in combination with optical routing and switching components allow for a large increase in bandwidth over electrical interconnects with a decrease in power consumption. The realization of photonic interconnects in silicon provides great advantages, as much of the experience is available in silicon processing. Techniques have been borrowed from the VLSI and MEMS toolkits and many new fabrication processes and techniques have been developed for silicon photonics platforms. In order for this technology to mature to a point of widespread industrial acceptance, there is still much work that must be done in a research environment. The work done in a silicon photonics research environment relies heavily on the use of specialized equipment for creating high precision, highly reproducible micrometer and nanometer scale features. In addition to the traditional requirements of VLSI and MEMS processing, nanophotonics has added restrictions on the quality and roughness of structures as the interactions between the light and the materials are very strong. In order to fabricate devices of the quality needed for silicon photonics research, researchers must be properly trained in fabrication techniques and how to use the fabrication equipment. The time required to completely master the operation of the fabrication can take years. However, basic tasks can be performed with a little training. Two of the major pieces of fabrication equipment, which will be covered in this work, are an RIE-ICP system and a PECVD system. These are a Samco® RIE-200iP and Samco® PD-220N, respectively. They are two pieces of very important pieces of equipment for most researches in the nanophotonics field. The first step to mastering the use of the equipment is learning about the background of the equipment. Because of this, the theory of how each of these tools operates is covered to provide background for new users and provide information to experienced users which may help in advancing their research. Understanding how the process works is just the first step to using the equipment. The next major component step is the actual operation of the equipment. By learning the setup of the equipment and the operation of its individual components much can be learned about machine operation and device processing. This will help in making process decisions and with process troubleshooting should a problem arise. After the operation and use of the equipment is understood the preparation of samples is important. So some example fabrication processes are described to provide examples of processing techniques. These examples also show some processing recipes, which are commonly used and should be familiar to users. These topics are covered in this document. Finally, in addition to the basic theory and operation a more detailed analysis of process parameters and variables will be presented. Along with fabrication, testing and characterization of devices is extremely important. While the types of testing and setups vary greatly, depending on the nature of the research, there are some tools which find broad use in nanophotonics research. Two of these are the spectrometer and the ellipsometer. The spectrometer allows for spectral characterization of light sources, whether this light is from testing equipment or from a fabricated device itself. The ellipsometer is able to determine the thickness and index of thin film layers on a sample. These two pieces are extremely important when doing material level work, which helps greatly in the advancement of new materials. As with the fabrication equipment, the theory, operation, and basic use of this equipment are discussed to facilitate testing of fabricated devices. The last important component of using fabrication equipment is proper maintenance. Without proper maintenance and servicing, the quality of results will not be repeatable. This will lead to slower research progress and more machine downtime for major repair. Because maintenance of equipment is very important and is often overlooked, it is also covered in this work. By combining good maintenance of equipment with proper use, it will lend itself to better, more reliable results in the nanophotonics research environment. This is presented throughout this work as the different components build on each other to show how they help to form a strong bond between the equipment and its users.