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Starting date:  March 1994
First step: December 1994
Main goal: To provide a CAD tool for silicon MOEMS design
User: National Institute for Microtechnology (IMT) Bucharest
Partner: ELREF Ltd. Bucharest
Second step: December 1995
Main goal: Chemo – optical silicon sensor chip
User: National Institute for Microtechnology (IMT) Bucharest
Partners: ELREF Ltd. Bucharest
Third step: December 1996
Main goal: Chemo – optical MOEMS for ammonia detection (demonstrator)
User: National Institute for Microtechnology (IMT) Bucharest
Partner: ELREF Ltd. Bucharest
Team: Mira Caldararu (project manager and device design and testing)
  Dr. Dana Cristea (device design and testing)
  Anca Paraschiv (device layout and testing)
  Florin Craciunoiu (technological design and manufacturing)
  Constantin Klier (encapsulation and device testing)
  Dr. Alexandru Vasile (testing hardware)
Project description
Software simulators for technological and geometrical parameter design
The output parameters of optoelectronic devices are determined by the technological and geometrical parameters. The variation of one internal parameter (junction depths, base doping, etc.) might change dramatically two or three output parameters (responsivity, bandwidth, rejection mode, etc.). The design of an optoelectronic device starts with the dependence of each output parameter to the input parameters, and continuos with the optimization of the input parameters so that the output parameters are in a specific domain required by the application. One can't experience very many values of technological parameters, as this is very expensive and the domain in which a technological parameter has to be changed so that the output parameter has a specific value is not known. On the other side, after a technological step, one must know how to adjust the forthcoming steps, knowing some of the measured resulted parameters. It results that a CAD instrument is necessary to be used in the design and technological monitoring of new optoelectronic devices. Chemo-optical phenomena, included in optoelectronic devices complicate the technology and imply that a simulator is absolutely necessary. In the figure the output curves representing the resulting photocurrent for a given photodiode, with the base width as parameter, are given.

ECOSEN Ltd. has designed more simulators in the domain of optoelectronic devices and chemo-optoelectronic sensors on a silicon structure including waveguides.

The simulators were written using the Borland TurboPascal 7.0 programming environment. They include the dependencies of the chemo-optical-electrical parameters to the technological and geometrical parameters for each device. The analogical relations were deduced. For the domains where this was not possible, numerical solutions were elaborated. A synthetic work of the solutions found in the literature and authors solution were performed, preserving the most direct relations between technological and output parameters. The authors used their experience in design and technology of sensors. A proper graphic is designed, to obtain a useful and easy to use tool (as might be seen in the figure bellow). A new project includes the design of the simulators in Visual Basic 6.0.

The input data are technological and geometrical parameters of the devices and input signals parameters (dopings, junction depths, optical area, etc.). In the first displays these data might be changed by the user. The output data (responsivity, noise, detectivity, size, etc.) are given as tables or curves. The user might choose the proper output data form which is more useful for him and the order of the displays, so that the design is achieved for a specific technology of the user: given dopings and junction depth ranges, process sequence and accuracy, photolithography requirements. The simulators were already used for technological and lay-out design. The scientists of ECOSEN Ltd. have designed more than 30 optoelectronic devices (photodiodes, photothirystors, optocouplers, solar cells, photovoltaic cells), which can be bought now from manufacturing company ROMES S.A.
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