Designing MEMS for manufacturing

Abstract

MEMS (micro electro-mechanical systems) are often expected to take a development as microelectronics did in the last 35 years. Several devices are already established in mass markets like acceleration sensors, gyros, pressure sensors, ink jet heads and the DLP micromirror array. On the other hand many companies have stopped their business after the telecom bubble. Others are struggling. Many dreams based on MEMS-devices that were not at all mature and could not be manufactured in high numbers. When a commercial product is the goal, several questions must be answered already in concept phase. The specifications must clearly reflect the requirements of the application. Performance and price must be competitive to any other technology. The relation between fabrication process and design is strong and mutual. The process must create all features of the devMEMS (micro electro-mechanical systems) are often expected to take a development as microelectronics did in the last 35 years. Several devices are already established in mass markets like acceleration sensors, gyros, pressure sensors, ink jet heads and the DLP micromirror array. On the other hand many companies have stopped their business after the telecom bubble. Others are struggling. Many dreams based on MEMS-devices that were not at all mature and could not be manufactured in high numbers. When a commercial product is the goal, several questions must be answered already in concept phase. The specifications must clearly reflect the requirements of the application. Performance and price must be competitive to any other technology. The relation between fabrication process and design is strong and mutual. The process must create all features of the device and the design must consider the limitations of the process. Only if the design is tolerant against all process variations reproducible performance can be achieved. And only if the design is robust in all process steps the devices can survive. Regarding the time and cost frame it is always preferable to change the layout rather than the process. This article looks at MEMS technology and identifies what has been adopted from CMOS, what is desirable to adopt and what needs new solutions. Examples are given in the fields of design, modeling layout, process, test, and packaging. Keywords: micro scanning mirror, micromirror array, optical MEMS, MOEMS, laser beam deflection, micromachining, out-of-plane comb drive, microsystem ice and the design must consider the limitations of the process. Only if the design is tolerant against all process variations reproducible performance can be achieved. And only if the design is robust in all process steps the devices can survive. Regarding the time and cost frame it is always preferable to change the layout rather than the process. This article looks at MEMS technology and identifies what has been adopted from CMOS, what is desirable to adopt and what needs new solutions. Examples are given in the fields of design, modeling layout, process, test, and packaging

What MEMS Research and Development Can Learn from a Production Environment

“…From a technological perspective, the aspects of packaging and system integration have been neglected, which play a crucial role during MEMS development. They are best considered right from the beginning of the development journey, as they can lead to requirements and boundary conditions significantly influencing the device design and fabrication process [ 37 , 49 ]. The use of available established solutions—where possible—allows reducing complexity and helps focus development efforts on the relevant parts.…”

“…MEMS research can highly benefit from introducing quality management fundamentals learned from a production environment. The key point to quality in production is testing, i.e., measuring the result of fabrication processes to ensure they stay within the specified limits [ 35 , 37 , 49 ]. Depending on their position within the process flow, measurements can be grouped to inline, end-of-line and product testing.…”

“…Fixing specifications is necessary when starting the transfer to production. However, it is good practice to start the specification process as early as possible [37,46,47].…”

“…While this close relationship is beneficial for the availability of tools and processes, the design of MEMS devices stays challenging. As discussed by Brück et al [ 36 ] and others [ 35 , 37 , 38 ], the fundamental difference with MEMS is the interdependency between device design and fabrication process due to the geometrical requirements for proper device functionality. While efforts are made to group closely related devices into technology platforms [ 39 , 40 , 41 ], a fine-tuning of the process flow for each device to meet application requirements is usually unavoidable.…”

“…Bieniek et al [ 47 , 48 ] apply this approach exemplarily on the development of an inertial sensor. Wolter et al [ 37 ] provide insight into the design and development of two exemplary optical MEMS devices with the aim of volume production comparing their experiences to CMOS manufacturing. The transfer of a MEMS research prototype toward a mass producible product is further described in detail by Fitzgerald et al [ 35 , 49 ] giving a plethora of hints and tips for commercial success.…”