Post-Fabrication Melting Procedure With I-Shaped Beams for Stiction-Free Release of 2-D Surface-Micromachined Micromirrors Equipped With Repulsive-Force Actuators

Zuo, Haoyi; He, Siyuan

doi:10.1109/jmems.2018.2844735

Cited by 9 publications

(10 citation statements)

References 44 publications

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“…MEMS micromirrors can be classified into two categories according to the mirror plate‘s fabrication method and the aperture size. The first type has the mirror plate and actuator in the same body with an aperture of normally <1 mm [1,2,3,8,20] and surface flatness of ROC (radius of curvature) of normally <1 m. The second type can achieve a large aperture (several millimeters) with a high flatness (ROC >10 m), in which the mirror plate and actuator are fabricated separately and then bonded together afterwards [21,22]. For numerous laser scanning applications, such as laser engraving and LiDAR, a large aperture (e.g., one millimeter to several millimeters) and high flatness are preferred to accommodate a higher laser power or lower the laser power density, as well as achieve a better collimation.…”

Section: Introductionmentioning

confidence: 99%

External Electromagnet FPCB Micromirror for Large Angle Laser Scanning

Periyasamy

Tan

et al. 2019

Micromachines

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An external electromagnet plus moving PM (permanent magnet) FPCB (flexible printed circuit board) micromirror is proposed in this paper that can overcome two limitations associated with the previous FPCB micromirror with a configuration of an external PM plus moving coil, i.e., (1) it reduces the overall width beyond the mirror plate, and (2) increases the maximum rotation angle. The micromirror has two external electromagnets underneath an FPCB structure (two torsion beams and a middle seat) with two moving PM discs attached to the back and a metal-coated mirror plate bonded to the front of the FPCB middle seat. Modeling and simulation were introduced, and the prototype was fabricated and tested to verify the design. The achieved performance was better than that of the previous design: a maximum resonant rotation angle of 62° (optical) at a driving voltage of ±3 V with a frequency of 191 Hz, the required extra width beyond the mirror plate was 6 mm, and an aperture of 8 mm × 5.5 mm with a roughness of <10 nm and a flatness of >10 m (ROC, radius of curvature). The previous FPCB micromirror’s performance was: strain limited maximum rotation angle was 40° (optical), the extra width beyond the mirror plate was 14.7 mm, and had an aperture of 4 mm × 4 mm with a similar roughness and flatness.

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Section: Introductionmentioning

confidence: 99%

External Electromagnet FPCB Micromirror for Large Angle Laser Scanning

Periyasamy

Tan

et al. 2019

Micromachines

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“…Hence there is no voltage difference between the mirror plate and the electrode underneath. As a result, no repulsive-force actuator is needed to push the mirror plate up when melting the beams, as is the case in the previously developed melted I-shape beam mechanism [26]. Therefore, the post-fabrication melted supporting beams mechanism can be widely used by general surface-micromachined large structure since repulsive-force actuators are not needed, which require a lot of extra space.…”

Section: Melting Proceduresmentioning

confidence: 99%

“…The simulation result shows that the voltage difference is less than 0.1 V when melting the supporting beams, which does not cause significant attractive electrostatic force to pull the mirror plate to touch the electrode underneath and cause stiction problem. So the repulsive-force actuators are not needed to push the mirror plate up to counter act the pulling force as the case in the previously developed melting beam mechanism [26]. Figure 3(a) shows an example of voltage distribution when melting the supporting beam 6.…”

Section: Melting Supporting Beamsmentioning

confidence: 99%

“…The postfabrication melted supporting beam is simply referred to as 'supporting beam' hereafter. The supporting beam mechanism is improved based on the previously developed repulsive-force aided melting I-shape beam mechanism [26]. Post-fabrication melting procedure with I-shaped beams in the design [26] requires aid of the repulsive-force actuators to push up the mirror plate and melt the last two supporting beams.…”

Section: Introductionmentioning

confidence: 99%

“…The supporting beam mechanism is improved based on the previously developed repulsive-force aided melting I-shape beam mechanism [26]. Post-fabrication melting procedure with I-shaped beams in the design [26] requires aid of the repulsive-force actuators to push up the mirror plate and melt the last two supporting beams. Without pushing up the mirror plate, the melting voltage will cause the potential difference between the mirror plate and the electrode layer underneath, which will generate a high attractive force to pull the mirror plate down and stick to the layer underneath.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Large aperture surface-micromachined rotating micromirror with the majority of dimples removed

Zuo¹,

He²

2019

J. Micromech. Microeng.

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This paper presents a surface-micromachined repulsive-force driven 1D rotating micromirror with a large aperture (1 mm). Two rotating beams are located on the bottom side of the mirror plate, while two repulsive-force actuators are connected to two middle sides to push the mirror plate up for out-of-plane rotation. Thus, no complex self-assembly structure is required to raise the mirror plate for rotation as most conventional surface-micromachined rotating micromirrors do. In order to increase the yield rate for the large aperture micromirror and avoid dimples used for preventing stiction during fabrication, six post-fabrication melted supporting beams are used along the circumference to increase the stiffness in fabrication, which are electrically melted and broken after fabrication to restore the initial stiffness. Only 12 dimples in the center of mirror plate are used for preventing operational stiction. The mirror's reflectivity is increased to 25% from 20% after removing the majority of dimples. 36 prototypes are fabricated and tested and none of them suffer from stiction problem. The 6.3° optical rotation is achieved with a settling time of 26 ms.

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