Project Assignment Spring 2023-2

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University of Florida *

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EEE5354L

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Jan 9, 2024

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111Equation Chapter 1 Section 1EEL5225 Principles of MEMS Transducers Project Assignment Fall 2015 Semester Initial Submission Due: Monday, 5/1, 11:59pm (full report) Final Submission Due: Thursday 5/4, 11:59pm (revised report, based on Dr. Arnold’s comments) In this project, you will design and analyze a MEMS accelerometer intended for football helmet concussion sensor, where impact accelerations of 10 – 100+ g are common (1 g = 9.8 m/s 2 ). The objective is to design a surface-micromachined mechanical structure to meet certain transducer performance criteria. The device will be designed within the fabrication constraints of the Sandia SUMMiT V process. The device should be designed to respond to linear accelerations in one direction. However, the sensing direction can be designed to be either in-plane or out-of-plane. The structure should include a proof mass and one or more compliant springs, thus forming a second-order mass-spring-damper system. For simplicity, the transduction mechanism will be ignored. The design goal is to maximize the flat-band sensitivity (displacement per input acceleration) while maintaining bandwidth and linearity constraints. Teaming Brenden, Trevor Norma, Sara Kaitlyn, Chloe Yiwen, Andy Chuki, Aakarsh Sahil, Brook You will indicate the percent contribution of each student for each section of the report. If there are disagreements on the individual contributions, please contact Dr. Arnold. Design goals  Maximize sensitivity (displacement per input acceleration)  Natural frequency ≥ 20 kHz  Off-axis sensitivity < 5%  Nonlinearity < 10% for maximum acceleration of 200 g  Total chip size < 10 mm 2 Design/Model Assumptions:  SUMMiT V process flow  Assume the following dimensional variations:  5% variation in all film thicknesses (including sacrificial oxide layers) and  0.2  m in all mask dimensions  Assume a damping coefficient corresponding to a quality factor of 100 Design Report: Each team will submit a PDF design report. Technical content, neatness, organization, and spelling/grammar will be part of the grading. The report should present all information, calculations, equations, assumptions, or other information used in the design. Grading: Technical Accuracy 30% Principles of MEMS Transducers Page 1 Prepared by D. Arnold April 3, 2023

Device Performance 20% Organization/Presentation 20% Spelling/Grammar 20% Comprehensiveness 10% Please remember UF’s academic honesty policy in the preparation of your project report as detailed in the course syllabus. All submissions will be checked by “Turnitin” for detection of plagiarism. Use a minimum font size of 11 point. Margins should be 1” top and bottom and 1” left and right. There is no page limit. The first page should be a cover page with a title and author names. The body of the report should be formatted with the following sections (please use this numbering/lettering scheme): 1. Device Overview A. Device Description Describe the overall geometry and operation of your device. Include pictures or drawings as necessary. Explain which layers of the SUMMiT V process are used to realize the structure. B. Design Approach Explain your design approach, i.e. a step-by-step description of how you approached the problem to meet the above parameters. C. Device Dimensions Show detailed drawings of the structure including dimensions (either on the drawing or in a table) 2. Device Design A. Lumped Element Model Show the equivalent lumped element model. B. System Parameters Calculate effective mass (m), effective spring stiffness (k), damping coefficient (b), and natural frequency of the system. C. Sensitivity Calculate flat-band tip deflection per acceleration D. Stress Limits Calculate maximum stress induced per acceleration. Ensure stress at 200 g does not lead to mechanical failure. E. Cross-Axis Sensitivity Calculate cross-axis sensitivities as ratio of primary and transverse spring stiffnesses F. Non-linearity Calculate non-linearity for 200 g acceleration. This may be estimated from error of small angle approximation G. Process Variability Calculate upper and lower bounds of C) and D) that could arise from process variations. 3. Process Flow Show the process flow including process steps, cross sections, and mask layouts for the device. Be sure to indicate the specific MASK NAME and LEVEL for each photomask layer (e.g. MMPOLY0, Mask 2). (See table in the SUMMiT V Design Guide.) 4. Device Performance A. Static Response Plot the static (flat-band) tip displacement vs. input acceleration. B. Dynamic Response Principles of MEMS Transducers Page 2 Prepared by D. Arnold April 3, 2023

Plot the magnitude and phase frequency response functions for tip displacement per acceleration. For the magnitude plot, use log-log scale and for the phase, use semilog scale (log for frequency , but linear scale for phase). Plot magnitude in disp/accel (not dB), phase in degrees (not radians) and frequency in Hz (not rad/s). 5. Summary of Contributions Provide a list or table that summarizes the percentage contribution of each team member to each portion of the design report. Ex: Device Overview (Name 1: 0%, Name 2: 100%) Device Design (Name 1: 25%, Name 2: 75%) … 6. References Include any references you used for your design. References: [1] S. D. Senturia, Microsystem Design (Kluwer Academic Publishers, Boston, 2000). [2] N. Yazdi, F. Ayazi, and K. Najafi, “Micromachined inertial sensors,” Proceedings of the IEEE, Vol. 86, pp. 1640-1659, 1998. [3] R. Legtenberg, A. W. Groeneveld, and M. Elwenspoek, “Comb-drive actuators for large displacements,” J. Micromech. Microeng., Vol. 6, pp. 320-329, 1996. Sandia SUMMiT V process information: See “L3 Fabrication, Part 2” and http://www.sandia.gov/mstc/_assets/documents/design_documents/SUMMiT_V_Dmanual.pdf Polysilicon mechanical properties See p. 196 in Senturia. Principles of MEMS Transducers Page 3 Prepared by D. Arnold April 3, 2023

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