This project provides an opportunity to develop an advanced surface coating technology for fabricating an anti-stiction, self-assembly monolayer (SAM) on silicon wafers for use in micro-electromechanical systems (MEMS). The work will advance the state-of-the-art in SAM fabrication by improving coating uniformity, providing conformal coverage of micron structures, and expanding the SAM molecule selection range, all of which lead to better MEMS stability, reliability, and functionality. It will also meet the navy requirements by delivering a robust anti-stiction SAM coating with high electrical conductivity along the molecule chain while being non-conductive between molecules ( 1MOhm resistance across the coating). However, achieving these binary characteristics is challenging because high electrical conductivity along the linear (hydrophobic) molecular chain can increase cross-molecule conduction. Therefore, we are proposing an advanced SAM fabrication process that combines traditional SAM fabrication with additional steps that provide better control of the monolayer self-assembly process, thereby allowing us to precisely engineer the monolayer structure at the molecular level. We developed and implemented similar SAM technologies in prior work and found them to produce repeatable, uniform, high quality coatings. The process will also be cost-effective and scalable for mass production. Micro-electromechanical systems (MEMS) fabrication has experienced rapid growth in the past decade due to its versatility and breadth of applications. However, one of the factors limiting its widespread use and reliability is the problem of stiction that may occur during fabrication and detrimentally affect MEMS operations. Stiction arises at the molecular level due to surface forces such as capillary action, hydrogen bonding, electrostatics, and van der Waals effects, which can dominate interactions at the micro-scale. Recently, applications using sub-nanometer SAM films have attracted attention in tackling stiction problems because of their high hydrophobicity, low surface energy, and compact packing structures that can inhibit capillary forces. These applications also provide coatings that exhibit low adhesion and friction, minimal energy loss, conformal coverage, and increased stability within a wide range of environmental conditions.
Benefit: The technology developed in this project will be used to support a wide variety of military and commercial applications. The goal of the project is to develop an advanced fabrication process for producing a self-assembly monolayer (SAM) on silicon wafers. SAM is at the heart of many physical, chemical, and biological processes and is one of the most fundamental processes for forming a functional structure. Scientists are increasingly using SAM coatings in a multitude of applications. Advances in the ability to design and control monolayer self-assembly can provide a path forward for meeting future MEMS manufacturing needs that could potentially revolutionize various industries. For example, researchers in the field of electronics are investigating the use of controlled molecular self-assembly to build new types of electronic switches and sensors, some of which could potentially replace todays dependence on silicon electronics. The pharmaceutical industry is also pushing hard to find ways to use controlled self-assembly to increase the efficiency of drug delivery processes. Others are seeking to use the technology to provide chemically protective layers to control surface reactivity. SAM coatings are currently used in the production of many types of micro-electromechanical systems (MEMS) devices including a variety of important military and commercial products. However, the current SAM coatings used to produce MEMS products often suffer from the problem of stiction that reduces MEMS stability and reliability. By providing new SAM anti-stiction coatings with improved electrically conductive performance, this project would go a long way toward effectively overcoming these problems. While industry has incorporated SAM technology into commercial products such as accelerometers and gyroscopes, the required stability and reliability of critical strategic sensors and other military applications necessitates additional improvements. The development of carefully engineered SAM coatings, made possible by using a specialized fabrication process as proposed in this project, would greatly improve MEMS product quality, reliability, and electrical performance. These new fabrication methods could be quickly scaled up and adopted by industry in the manufacture of more powerful, capable, and reliable MEMS devices for a variety of critically important military and commercial markets.
Keywords: self-assembly monolayer, self-assembly monolayer, coating, micro-electromechanical system, fabrication, MEMS, SAM
