Capstone Project
| Group | 2008-07 | Status | completed |
| Title | Large Scale Integrated (LSI) MEMS Circuit: Design of a MEMS-based charge pump for +50 V biasing | ||
| Supervisor | Drs. P. Valizadeh and G. Cowan | ||
| Description | As an outcome of the intense investment in the area of MicroElectroMechanical System technology (i.e. MEMS), past decade has been witness to the creation of a large number of innovative micro-electromechanical devices. So far, problems in integrating these newly developed family of devices with the processing, communication, control, and readout circuitry have by large stalled the maximum exploitation of their resources. In addition, inherent requirement of some of these technologies have further challenged the commercialization of these solutions (e.g., the need for high DC voltages and low pressure ambient in the case of capacitively-transduced MEMS). Operation of many electrostatically-activated MEMS devices, such as signal processors and inertial sensors, is reliant on the on-chip availability of large DC voltage (>50 V). Although, charge-pumps are suitable structures for achieving high DC voltages, the reduced junction breakdown-voltage of today�s CMOS technology and body-effect complications restrict the maximum output voltage of these integrated circuits to voltages lower than the required. In order to circumvent these restrictions, micro-electromechanical switch architectures are proposed to replace the ordinary MOS-based charge-pumps. In this project, students will engage in designing suitable switch architectures and devising the required modifications to the conventional charge-pump circuits. Realistic mechanical/electrical switch and circuit simulations based on the possibilities offered by the technology of choice (preferably 0.25 �m CMOS or a traditional surface micromachining process), will be carried out. Based on the results of simulations on a variety of switch structures (e.g. clamped-clamped, meandered, cantilever�), the type and dimensions of the mechanical structure of the highest degree of reliability and compatibility with biasing requirements are selected. Realistic process flow and layout for the fabrication of MEMS-based LSI circuits are then developed. In this layout/process-flow design, process monitoring structures and steps will be also dealt with. Considering the time and budgetary constraints, an actual fabrication and testing of the designed circuits may be carried out through CMC. |
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| Student Requirement | Students have already passed ELEC 311 and ELEC 321. In addition, they either have already passed ELEC 421 and ELEC 424 or take them during Fall 2008 semester. Developing and understanding for the process flow in microelectronic fabrication and familiarity with layout design criteria of integrated circuits are instrumental to the success of this project. Students should be able to understand and analyze the maximum voltage constraint of a CMOS pair. To handle this multidisciplinary project, a basic knowledge of Mechanics is also required. Analysis of mechanical switches using mass/spring/damper models is needed. |
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| Tools | MATLAB: for mechanical simulation. PSPICE: for modeling the circuit operation based on electrical models for the mechanical switches. Cadence: for layout design. | ||
| Number of Students | 3 | ||
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