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Web-based Design Tools for MEMS-Process Configuration Kai Hahn and Rainer BrŸck University of Siegen, Hšlderlinstr. 3, D-57068 Siegen, Germany Phone: +49 271 7402377 Fax: +49 271 7402473, Email: email@example.com In the area of physical microsystem design that in li- ABSTRACT thography-based technologies is concerned with the design of mask layout geometries, the typical design cycle is The micro electromechanical systems (MEMS) industry dominated by the fact that the three-dimensional nature of is characterized by small and medium sized enterprises the products calls for a particular sequence of processing (SMEs) specialized on products to solve problems in spe- steps and parameters to be specified for each design object. cific domains like medicine, automotive sensor technology, This results in the circle model for MEMS physical design. etc. In this field of business the technology driven design It is characterized by the following circular design flow: approach known from micro electronics is not appropriate. • Generating activities creating the mask layout Instead each design problem aims at its own, specific tech- geometries for the design object and the specific nology to be used for the solution. The variety of technolo- process step sequence to be performed in order to gies at hand, like Si-surface, Si-bulk, LIGA, laser, precision generate the appropriate orthogonal extension of engineering requires a huge set of different design tools to the design object during production. The of process be available. No single SME can afford to hold licenses for step specification part will be in the focus of this all these tools. This calls for a new and flexible way of de- paper. signing, implementing and distributing design software. • Checking activities deriving a consistent set of de- The Internet provides a flexible manner of offering soft- sign rules from the process sequence and applying ware access along with methodologies of flexible licensing it to the mask layout in order to find rule violations. e.g. on a pay-per-use basis. INTERLIDO is a tool suite for If violations are detected, the design will have to be process specification and layout verification for lithography modified. based MEMS technologies to be accessed via the Internet. • Changing activities used to determine what sort of The first version provides a Java implementation of LIDO- changes will have to be made in order to turn the PEdit, a graphical configuration system for process step design into a correct version. This may include sequences. The implementation is based on JavaBeans mask layout changes, process specification changes component technology. or changes in the higher level design. For more details of the circle model, see [1,2]. Figure 1 Keywords: MEMS physical design, process configuration, gives an alternative view of this model, showing the design INTERNET tool access, component technology, JAVA. flow as two concurrent interwoven circles of layout and process design. The process editing tool to be presented MODELS OF PHYSICAL MEMS DESIGN shortly is used to support the process design cycle. Micro system technology promises to be one of the key (Initial) Process Configuration: technologies for the 21st century. As it is the case for all Process Editor Process highly complex technical systems computer based design Consistency Check support is mandatory for this. Concerning the design sup- Process Steps Materials Consistency port for this field we currently face the following situation: ? • There is a strong need for design support and an (Initial) Layout Design: Design Rule Check Process Steps Materials Error material even stronger lack of such tools at this point of : Layout Editor 1 DRC Layout Process Formal time. Design Design Process • The structure of the industry concerned with design Error on metal: angle < 32 deg Description Technology Optimisation and production of micro system technology prod- of Process process accelerometer attibutes Alternatives ucts comprises a prototype of the emerging industry Optimisation process steps resist dep. (nickel, pmma, gold) for microsystems. • The design style is problem-oriented - as opposed to the technology oriented design style known from todayÕs classical microelectronic systems design - which turns out to be the appropriate approach for Figure 1: MEMS physical design flow microsystem design. Each of the steps shown in this figure can be supported Internet access capabilities especially for MEMS design by specific design tools. Each of these tools is an independ- tools will be presented later in this article. ent software module, used to assist the user in a particular subtask of the whole design cycle. The degree of automa- THE PEDIT PROCESS EDITING TOOL tion provided may differ substantially for each of the tools. The term assistants is used to denote this sort of independ- LIDO-PEdit enables the configuration of a process se- ent software modules. The LIDO-system presented in the quence considering the requirements of the specification following section thus can be regarded as a collection of and the layout design of the intended microstructure. The weakly interacting assistants. process arrangement is performed graphically in an editor window. The user selects and arranges icons on the editor (INTER)-LIDO-MEMS DESIGN SYSTEM window representing design process elements like process steps, materials etc. from libraries based on the specific Currently there is hardly any CAD support for the de- design task he/she is performing. Icons can graphically be sign process as described. A prototype approach for design connected to complete process sequences. Each icon is as- verification based on the recognition of design properties signed to process or technology data such as design rules, restricted to LIGA technologies is presented in . Except process parameters or economic properties. This data is design capture tools (like AutoCAD) there are no dedicated provided by process experts using the process description commercial tools for microstructure design today. The tools language LIDO-PDL.  used for microelectronics IC design are based on fixed LIDO-PEdit additionally provides the option to check technology data accessed via design rule interfaces. The the current process configuration for consistency (like com- user has no opportunity to influence the fabrication process. patibility of process steps or materials, sequence rules, as- Correctness with regard to process or layout rules as a re- signment rules etc.). This check is normally necessary be- sult of this tool configuration can only guarantee that the cause the designer need not to know internal properties of following fabrication of microstructures can be performed all process elements. As alternative process branches are without running into problems caused by design errors. possible to describe (e.g. in case of alternative process se- The LIDO system is the first approach to physical de- quences for different machines) an optimization is provided sign support that takes the requirements of microstructure to find the optimum flow with respect to predefined objec- design into account . On the one hand LIDO provides tive functions (e.g. cost, time etc.). This reacts to the de- means to determine the technological process to apply in mands of designers who want to learn about the economic order to fabricate the designed microstructure in LIGA or implications of a process layout as early as possible. . silicon techniques. On the other hand the mask layout can LIDO-PEdit consists of be verified with respect to design rules derived from the • the graphical user interface that provides the editing process configuration. windows used for selecting process icons and ar- ranging them into process sequences, Process Descriptions Design LIDO-PDL Initial Layout • a process module library containing LIDO-PDL Constraints GDS II representations of generic process elements that are linked to the editing icons LIDO-PEdit LIDO-Check Graphical Process Layout • consistency checking modules used to assure that Editor Verification only valid process sequences can be used to gener- ate LIDO-PDL process descriptions Process Checking • LIDO-PDL generation routines turning a given Elements Assistants consistent process sequence into a LIDO-PDL LIDO-Manager Results process description, if desired in an optimized Design Validation fashion. Control Layout &Process Figure 3 shows an overview of the LIDO-PEdit system. The modular system structure lends itself to a component- Figure 2: INTERLIDO system overview based implementation. The modular software structure of LIDO-PDL, how- The system as a whole is composed of a set of assis- ever, keeps transparent for the user, who will only be pro- tants. It consists of a common user interface and a common vided with the user interface that looks like the example technology and geometry database, both combined in the given in Figure 4. It is roughly the same for the original LIDO-Manager. Fig. 2 shows a system view of the LIDO version of LIDO-PEdit and for the new one that makes IN- system. The user interface offers two major applications: TERNET access possible. LIDO-Pedit - the graphical process configuration editor and LIDO-Check. - the microstructure design rule checker. Currently the LIDO-system is completely re- implemented as componentware to be accessible via the Internet. The benefits of component based software with Graphical User Interface implements a set of software components, the application developer configures these components in an application dependent manner and connects them to form complete Process Editor Process applications. The customer, finally, is able to perform mi- Module Internal Process Library nor configuration modifications. The term ÒApplication Rule Consistency Family EngineeringÓ denotes the development of a com- Check plete framework of components useful for a specific set of Layout Rule applications, like, e.g. micro engineering physical design. Consistency Check LIDO-PEdit An important precondition for a useful set of components is LIDO-PDL that they are well-adapted to each others. LIDO-PDL Output Process Converter Optimisation optional component based software development LIDO-PDL LIDO-PDL component family enginiering Process Process development applikation development applikation Description Description (optimised) customizing Figure 2: LIDO-PEdit system overview composing customizing influence influence component developer applikation developer customer Fig. 4: Steps of component based software development Structure- and physical specifikation Structure specifikation, physical specifikation Intra/Internet and the design expert influence component the selection, customizing and composing of beans directory for MEMS Talk design Assistant assistants Figure 3: LIDO-PEdit session screen shot makeBeans Make COMPONENT TECHNOLOGY talkBeans Change Assistant Assistant As has been pointed out in the previous chapters in mi- checkBeans Check cro engineering the design process has to be tailored to- Assistant changeBeans wards every specific design object. As a consequence of this, specific design assistants have to be selected for each final fabrication beans beans beans beans assistants specifikation design task and especially adapted towards the restrictions developing selecting customizing composing customizing to be met in each particular case. To achieve this, compo- nent-based software design is currently the method of the choice. It is targeted towards realizing so-called software Fig. 5 Component based design assistants components, executable pieces of software with a clearly defined interface, defined interoperability- and autonomy criteria, as well as the proof of reusability . Fig. 5 shows an integrated view of the circle model for Componentware is generally understood to be a collec- MEMS design. The Intranet/Internet component directory tion of interacting components. Design assistants in IN- for physical MEMS design assistants contains various TERLIDO are realized as componentware based on the beans for the basic tasks to be performed during design. component technology JavaBeans by SUN Microsystems. They are the building block for the process of dynamically JavaBeans is a platform independent component architec- generating design assistants. The selection, configuration, ture for the Java Application Environment . Fig. 4 shows and composition processes are controlled by the given for- the general procedure to be followed during component- mal specification of the design object and the knowledge of oriented software development. The component developer the design expert. At the end of this process there are de- sign assistants that will be selected based on the design re- strictions at hand, and that will be used as componentware LIDO-PDL descriptions. The LIDO-PEdit functional com- to support the design process. ponents will be available on the INTERLIDO-Server and For design assistants and their components different li- will access the technology related information via the net. censing scenarios may be applied. Components might be The user interface is realized as a JAVA-applet to be run on freely accessible to be downloaded via the Internet. After the user«s client computer. In this manner not only sophisti- downloading the user might use the component freely, re- cated licensing and software maintenance mechanisms can stricted to a certain range of time, or for a fixed number of be provided. It is also possible to implement a separation times. This provides especially SMEs with a possibility to between design data and technology data that is frequently create proprietary MEMS-Beans, hence commercializing desired by both design and technology providing institu- their know-how on some kind of pay-per-use regime. At the tions. same time component technology offers an interesting op- portunity for various cooperating software development CONCLUSIONS AND OUTLOOK scenarios, either between industry companies, or companies and research institutes. Design support for MEMS physical design based on the The INTERLIDO is a first prototype of a component- circle model is best provided by a set of loosely coupled based MEMS physical design tool. At this point of time the assistants. These assistants lend themselves to implementa- dynamic creation of problem-oriented beans has not yet tion using component technology. Using JavaBeans for this been realized. INTERLIDO is currently used to demon- purpose provides Internet-access facilities for the compo- strate the robustness of a component approach and to show nents as an add-on. This can be utilized to realize net-based that it can really be useful and not prohibitively limited software access. Providing a large base of various assistants from a performance point of view, to provide tools that op- for different technologies and different subtasks of the erate merely based on JAVA across the Internet. In addition physical design stage may be the basis of a Òphysical design not all of the LIDO components have been turned into broker serviceÓ providing especially SMEs with tools and components by now. LIDO-PEdit is the first part that is technologies for any MEMS solution they intend to create. available based on this new technology. Except extending and completing the INTERLIDO component base, research work in Siegen is currently fo- cusing on realizing this sort of Internet-based service. Design INTERLIDO -Server Technology Input/Output Data Flow Data Flow WWW- JAVA- Design WWW- REFERENCES User Provider Server Interface Design Data  BrŸck, R., Hahn, K., Reusch, B., Layout Verification Design LIDO Design Tools for MEMS Physical Design, Proc MSM 98, April Project Software 1998. INTERNET  BrŸck, R., Schumer, C.: Internet MEMS design tools based on component technology, Proc DTM 99, Paris, User Technology Provider 1999.  Buchberger, P., Eggert, H., Scherer K. P. MIDAS: Ein wissensbasiertes System zur UnterstŸtzung des ferti- Figure 7: INTERLIDO-network software access gungsgerechten Entwurfs von LIGA-Strukturen. Proc. 3. Workshop "Methoden und Werkzeugentwicklung fŸr den INTERLIDO Mikrosystementwurf", pp. 72Ð81, 1996.  Hahn, K., BrŸck, R. An Approach to Layout and An overview of the INTERLIDO system has already Process Verification for Microsystem Physical Design. Mi- been presented in Figure 2. crosystem Technologies, pp.82-90., 1997. The LIDO-PEdit system is currently available as an op-  BrŸck, R., Hahn, K., Priebe, A. Design Rules for erational prototype of an Internet based design assistant. An Silicon Based Micromachining Processes. Proc. Microme- implementation in JAVA has been realized and is accessi- chanics Europe 1996, Barcelona, 1996. ble via http://www-ttec.rs.uni-siegen.de. An in-depth de-  BrŸck, R., Hahn, K. MEMS Process/Design and scription of LIDO-PEdit emphasizing its features to support Optimization using Economical Constraints, Proc. MICO process sequence design taking economic aspects into ac- SYSTEM Technologies 98, pp. 479-484, 1998. count is available in .  C. W. Krueger. Software Reuse. ACM Computing Here we only give some remarks on the process of using Surveys, 24(2), June 1992. the INTERLIDO-system via the Internet. Figure 7 shows  J a v a B e a n s API specification, the principles of Internet-based software access, as they are http://www.javasoft.com/beans/docs/beans.101.pdf, Sun realized in INTERLIDO. The INTERLIDO-Server is a bro- Microsystems Computer Company, 1997. ker system that is used to bundle tools, technologies and  C. Schneider, A. Priebe, R. BrŸck, C. Schumer, user access across the net. Technology providers will pro- Computer aided design tools for economical MEMS fabri- vide their design related knowledge in form of icons and cation processes, Proc. DTM 99.
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