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Author: search.filters.author.Chen, Wenhao

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    A Pure CMOS Stack Electrostatic Micromirror Featuring Simplified Fabrication and Stress-Adjusted Modeling
    (2025-01-01)
    Chen, Wenhao
    ;
    Tavakkoli, Hadi
    ;
    Zhao, Bin
    ;
    Zhang, Maojie
    ;
    Piyawattanametha, Wibool
    We report a pure CMOS stack-made comb-actuated electrostatic micromirror for non-resonant scanning using a standard 0.18 μm 1-polysilicon 6-metal CMOS foundry process without complex post-processing steps. The staggered vertical combs are formed by different metal layers to provide a nonlinear electrostatic torque, enabling the device to achieve a 12.4° optical scan angle under 70V with a mirror size of 0.4×0.4 mm<sup>2</sup>. Considering CMOS process-induced stress, a modified theoretical model of the comb actuators agrees with experimental data, which gives a guideline for the design optimization of non-resonant CMOS-MEMS mirrors. This innovative integration of comb-drive actuator and mirror structure within the limited thickness of the standard CMOS stack (11 μm) and improved manufacturability boost a new generation of compact, high-performance optical MEMS devices.
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    Theoretical modeling and experimental investigation of in-phase resonant MEMS mirrors with cascaded structures
    (2024-05-01)
    Chen, Wenhao
    ;
    Luo, Huahuang
    ;
    Tavakkoli, Hadi
    ;
    Duan, Mingzheng
    ;
    Piyawattanametha, Wibool
    This paper proposes an efficient nonlinear one-dimensional (1D) compact mass-damper-spring model to predict the dynamic response of electrostatic resonant micro-electro-mechanical system (MEMS) mirrors with cascaded structures. The time-dependent damping moment due to viscous shear and pressure drag is computed using semi-empirical analytical equations for comb-drive structures and device frames. Nonlinear electrostatic force induced by the comb drives is efficiently acquired based on the hybrid method. The optimized device is fabricated using MEMS fabrication processes based on a 4-inch silicon-on-insulator wafer. The proposed compact model with the measured key parameters from the fabricated device shows excellent capability to accurately predict nonlinear dynamic responses of the fabricated device, including parametric excitation and hysteretic frequency response, with an average error of less than 5%. In particular, our 1D model is three orders of magnitude faster than the conventional finite element method model (0.8 s versus 1 h), enabling efficient system-level optimization of the critical design parameters. Based on the parametric study, electrode gap distance and torsion spring width are found to be two critical design parameters and dimensional analysis is conducted for design optimization with scan angle enhancing from 16.8° to 24° compared with the first design.
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    Theoretical and Experimental Study of Comb-Actuated Mirror with Cascaded Structures
    (2023-01-01)
    Chen, Wenhao
    ;
    Luo, Huahuang
    ;
    Duan, Mingzheng
    ;
    Tavakkoli, Hadi
    ;
    Piyawattanametha, Wibool
    For the first time, we present a two-dimensional theoretical model for one-dimensional comb-actuated MEMS mirror with cascaded structures. The numerical model including different damping mechanisms and nonlinear capacitive force is validated with experiment results. Stability analysis is conducted to simulate the nonlinear hysteretic frequency response. The model proposed can be a guideline for designing multi-degree-of-freedom nonlinear parametric-excited MEMS mirror with high frequency and large scan angle.
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    Design Optimization of CMOS- MEMS Staggered Vertical Comb Based Micro Scanners
    (2022-01-01)
    Chen, Wenhao
    ;
    Duani, Mingzheng
    ;
    Tavakkoli, Hadi
    ;
    Luo, Huahuang
    ;
    Zhao, Bin
    For the first time, we propose a novel CMOS-MEMS staggered vertical comb based micro scanner (SVC-MS) for ID static out-of-plane rotation using CanSemiconductor 0.18μm IP6M, TSMC CMOS foundry process. Based on compact model, the parametric analysis shows the torsion spring width and the actuator thickness are two critical parameters in term of design, and design optimization using dimensional analysis can be conducted for improving the rotation angle(Ooptical=19.26°) and figure of merit (FoM=O.6) by 400% and 150% compared with the first design. The optimized design shows miniaturization with a mirror size of 800μm and a higher FoM of 0.6 among previous designs. In addition, critical ratio of geometry for increasing the input-output response with a lower voltage is found, which can improve the actuator's performance.