Out-of-plane Bimorph MEMS Micromirrors for Large Angle Beamsteering
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Solution Overview
Problem
Current MEMS micromirror technologies fail to achieve large angle beamsteering with high fill-factors, as they typically limit tip or tilt angles to less than 20 degrees and do not incorporate piston motion, which is essential for broadband steering and imaging applications.
Innovation Solution
The development of out-of-plane bimorph MEMS micromirrors using foundry processes and in-house fabrication, employing serpentine and center-anchored multi-beam designs that leverage residual stresses and coefficient of thermal expansion differences to enable large angle deflections, tip, tilt, and piston motion while maintaining high fill-factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional MEMS micromirror designs are used, then manufacturing simplicity is maintained, but tip/tilt angle is limited to less than 20 degrees
Solution Approach 1:
The micromirror is divided into multiple segments or zones that can be independently actuated. This segmentation allows each zone to contribute to the overall tip/tilt angle, enabling large angle beamsteering while maintaining a relatively simple overall device structure that can be fabricated using standard MEMS processes.
Solution Approach 2:
The invention transitions from in-plane mirror rotation to out-of-plane mirror deflection. By bending the micromirror substrate out of its original plane using compliant hinges or flexible supports, the device achieves large tip/tilt angles without requiring complex rotational mechanisms, thus resolving the contradiction between angle and complexity.
2Area of moving object
If conventional single-element designs are used, then device simplicity is maintained, but fill-factor is less than 90%
Solution Approach 1:
Multiple micromirror elements are merged into a single integrated array structure that functions as one unified device. This merging approach achieves high fill-factor by eliminating gaps between individual elements while maintaining independent actuation capability through segmented control electrodes, thus achieving both high area utilization and functional complexity.
Solution Approach 2:
The micromirror array is designed to perform multiple functions simultaneously: beamsteering, optical correction, and scanning. By integrating these functions into a single device structure with high fill-factor, the invention eliminates the need for separate components, thereby achieving high area utilization without proportionally increasing device complexity.
3Adaptability or versatility
If conventional MEMS designs are used, then fabrication simplicity is maintained, but piston motion capability is absent
Solution Approach 1:
The invention changes the mechanical parameters of the micromirror support structure by introducing compliant hinges and flexible beams that allow out-of-plane motion. This parameter change enables piston motion capability while maintaining compatibility with standard MEMS fabrication processes, thus achieving versatility without sacrificing ease of manufacture.
Solution Approach 2:
The micromirror structure employs composite materials with different stress characteristics to enable piston motion. By combining materials with complementary mechanical properties in a layered structure, the device achieves both piston motion capability and broadband steering functionality while remaining manufacturable through conventional MEMS processes.
4Length of moving object
If large angle beamsteering is achieved through conventional methods, then tip/tilt angle is improved, but piston motion and high fill-factor are not achieved simultaneously
Solution Approach 1:
The micromirror is segmented into multiple independently controllable zones that can be actuated differentially. This segmentation enables both large tip/tilt angles through asymmetric actuation and piston motion through symmetric actuation, while the integrated array design maintains high fill-factor, thus achieving all three capabilities simultaneously.
Solution Approach 2:
The invention utilizes out-of-plane deflection of the micromirror substrate to achieve large tip/tilt angles, replacing conventional in-plane rotation. This dimensional change also enables piston motion through controlled substrate bending, and the compact out-of-plane structure allows for high fill-factor arrays, thereby achieving all desired functionalities together.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These designs achieve scalable, high fill-factor arrays capable of large angle beamsteering, suitable for broadband steering and imaging applications, replacing conventional gimbal systems with nearly conformal, low-voltage, and adaptable MEMS devices that can integrate electrostatic and electrothermal actuation for various optical applications.
Implementation Method 1
These structures exhibit high, out-of-plane deformations as either a MEMS electrostatic and electrothermal actuators... The design methodology capitalizes on the inherent residual stresses in bimorph structures
Implementation Method 2
The design methodology capitalizes on the inherent residual stresses in bimorph structures which possess different coefficients of thermal expansions (CTE)
Implementation Method 3
These structures exhibit high, out-of-plane deformations as either a MEMS electrostatic and electrothermal actuators
Implementation Method 4
These structures exhibit high, out-of-plane deformations as either a MEMS electrostatic and electrothermal actuators
Data Source
AI summary
An actuator element of a MEMS device is provided, which is fabricated using surface micromachining on a substrate. An insulating layer having a first portion contacts the substrate while a second portion is separated from the substrate by a gap. A metallic layer contacts the insulating layer having a first portion contacting the first portion of the insulating layer and a second portion contacting the second portion of the insulating layer. The second portion of the metallic layer is prestressed. Alternately, the actuator element includes a first insulating layer separated from the substrate by a gap. A metallic layer has a first portion contacting the substrate and a second portion contacting the insulating layer. A second insulating layer contacts a portion of the second portion of the metallic layer opposite the first insulating layer, where the second insulating layer is prestressed.