Methodik der Produktentwicklung in der Mikrosystemtechnik

Right from the beginning, a few decades ago, MEMS (Micro-Electro-Mechanical-Systems) technology was regarded as a worldwide key technology with enormous potential for the 21th century. The market for MEMS has grown around 20% per year over the last decade and MEMS products are meanwhile used in various fields, e. g. in the automation, automotive or bio-medical sector, to enhance conventional applications or to open new areas of technology. MST (Micro-Systems-Technology) allows the production of such systems with extreme mechanical precision and high repetition accuracy. The placement of new innovative products on these markets requires a large investment in research and development as well as a systematic organisation of both product development and production chain to accelerate the process from the start of development to the market introduction of MEMS. Therefore it is important to master the actual challenges for the industry: the trend towards globalisation, growing complexity of both products and processes, the need for knowledge and experience management, increasing commercial pressures and the request for sustainable products. Up to now structured development processes for MEMS are not common practice due to the novelty of products and manufacturing technologies. Only a few systematic procedures are known but not established and the exchange of knowledge of development proceedings is reduced. Products are often based on brilliant ideas without a systematic approach. Continuous improvement to support a shorter development time is often not applied sufficiently. Experience in other disciplines, e. g. mechanical, electrical or software engineering, has shown that a well structured development process allows the exploitation of the wide possibilities of MEMS, the organization of knowledge for further developments and the development of marketable products with a high reliability. The main target of this thesis is to close this gap by supplying designer in practice with a methodology for the development of innovative MEMS products. Furthermore the development procedure is supplemented by methods to assist the designer in dealing with the main challenges of MEMS development.

Emphases of the thesis
This thesis focuses upon four areas: An analysis of the actual state and requirements of MEMS technology, a comparison of methodologies in other areas, the suggestion of a new approach to MEMS design and the provision of supporting methods.

Actual state of MEMS technology
MEMS technology deals with the integration of diverse micro technologies in complex and highly integrated systems under continuously developing boundary conditions. Successful development of MEMS demands a customised and rapid development process and requires attention to their special characteristics: essential cooperation of experts of various fields, a wide range of manufacturing technologies and technology-driven development. The field of MEMS was developed by adapting microelectronic manufacturing technologies and is still immature. MEMS technology integrates several domains, e. g. micromechanics, microelectronics or microoptics, in small package dimensions and therefore demands interdisciplinary cooperation of experts of diverse disciplines. MEMS products are produced in a wide range of technologies and processes usually based on silicon or plastic. Materials and manufacturing technologies are continuously improving. The close interdependence between product and production technologies asks domain experts to acquire both technological and design process knowledge to become MEMS experts. Furthermore they have to keep up with actual technological changes much more than in traditional disciplines. This requires lifelong learning far beyond continuing training in other disciplines to keep an actual level of knowledge, because designers have to observe their own and neighbouring domains throughout their professional life. Interrelations and interactions in highly complex MEMS must be considered in an appropriate way. An extensive study of MEMS design emphasises the need for guidelines for geometry, manufacturing and materials as well as assistance in the understanding of the entire system. The actual state and the needs of MEMS technology lead to requirements to a methodology for MEMS design.

Methodologies in other areas
Methodologies for product development are common in diverse disciplines. An analysis of methodologies in mechanical engineering, electronics, software engineering, control engineering and mechatronics shows that the approach of the VDI-guideline 2206 for mechatronics comprises a suitable basis for a MEMS development process.

A Methodology for MEMS Design
The MEMS development process suggested in this thesis is shown in Figure 1. This general development process starts with the generation of an interdisciplinary system concept. It is continued by the most important part of MEMS development that differs significantly from other domains: a parallel development of the systems components in diverse domains and the manufacturing technology. A proper development procedure in this phase is fundamental to avoid parasitic interactions between the elements of the system and its environment. The concluding system integration verifies the desired characteristics of the product. The development process is embedded in the product lifecycle to incorporate knowledge and demands from different stages of the product's life. Simulation as early as possible helps to predict the properties of the system and supports both integration and supply of efficient technology. A well-defined and continuous MEMS development process like the classic process for mechanical tasks is often not possible. It is disturbed by the fastchanging environment and the simultaneous development of the manufacturing technology. The development process is therefore characterised by iterations. The consideration of parasitic influences and the simulation of the system and its components at an early stage is one way of forecast of properties and prevention of iterations. The described general process must be precisely specified and adapted for the demands of specific product developments.

Supporting Methods
The development process can be supported by many methods used in other disciplines. Moreover methods are useful in the potential weak points of MEMS design: The collection and preparation of knowledge in continuously developing conditions and the handling of internal and external interactions of the system's components and its surroundings. The first task can be solved by systematic supply of information about physical effects, design catalogues and regularly updated guidelines about geometry, manufacturing limits and materials. The examination of the entire system and the consideration of aspects of system integration can be achieved through the use of a newly developed working structure and a corresponding Design Structure Matrices (DSM). Both methods clarify the dependencies between the components of the system and therefore enable the designer to regard all influences and to be sure to gather all information from diverse domains influencing the design process.