Vertical Hinge MEMS Mirror for Precise Tilt Control
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Solution Overview
Problem
Existing MEMS display devices with horizontal hinges face challenges in achieving precise positioning and high temperature durability due to limitations in controlling the tilt angle and residual stress of the hinge, which affects the mirror's ON and OFF positions.
Innovation Solution
A MEMS device with a vertical hinge made of doped amorphous silicon, featuring a vertical support and hinge tabs, where the gap between the stopper and hinge tab is accurately controlled by a sacrificial layer deposition, allowing precise tilt angle adjustment and residual stress management from compressive to tensile conditions, ensuring the mirror's neutral position corresponds to the OFF position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a horizontal hinge is used in MEMS display device, then the structure is simpler to manufacture, but the positioning precision and tilt angle control deteriorate
Solution Approach 1:
The patent inverts the traditional horizontal hinge configuration to a vertical hinge structure. The vertical hinge extends in the vertical direction perpendicular to the substrate, with the mirror mounted on its free end. This inversion allows the hinge to achieve precise positioning and controlled tilt angles while maintaining manufacturing feasibility through standard semiconductor fabrication processes.
Solution Approach 2:
The patent transitions from a horizontal hinge arrangement to a vertical hinge arrangement, utilizing the vertical dimension perpendicular to the substrate plane. This dimensional change enables better control over the mirror's tilt angle and positioning precision while allowing the hinge to accommodate stress management features and stoppers for precise angular control.
2Temperature
If the hinge material has high temperature durability, then the device can withstand high temperatures, but the residual stress control becomes more difficult
Solution Approach 1:
The patent employs silicon nitride as the hinge material, which offers both high temperature durability and controllable residual stress properties. By adjusting deposition parameters and doping concentrations during fabrication, the residual stress in the silicon nitride hinge can be precisely controlled to achieve the desired mirror tilt angles while maintaining structural integrity at elevated temperatures.
Solution Approach 2:
The patent introduces doped regions within the hinge structure to locally modify material properties. By creating areas with different doping concentrations, the hinge achieves optimized stress distribution and temperature resistance in specific zones, allowing precise control of residual stress while maintaining overall high temperature durability.
3Reliability
If the hinge structure is compact and strong, then it endures multiple cycles without failure, but the tilt angle adjustment precision may be reduced
Solution Approach 1:
The patent segments the hinge structure into distinct functional zones: a rigid base region for structural support and cycle endurance, and a more compliant region near the mirror mounting area that allows precise tilt angle control. This segmentation enables the hinge to maintain structural integrity over multiple cycles while achieving accurate angular positioning.
Solution Approach 2:
The patent introduces a stopper structure as an intermediary element between the hinge and the mirror mounting interface. This stopper acts as a mechanical constraint that precisely defines the maximum tilt angle, ensuring accurate angular control while allowing the hinge itself to maintain its compact and strong structure for reliable cycle endurance.
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
The solution enables precise control of the mirror's tilt angle, enhances the MEMS device's ability to withstand high temperatures, and provides a strong, compact hinge structure that endures multiple ON-OFF cycles without failure, preventing electrical shorts and maintaining accurate display performance.
Implementation Method 1
The movable mirror is electrostatically attracted to the electrode responsive to application of a voltage between the electrode and the movable mirror
Data Source
AI summary
A micro-electro-mechanical systems device includes a substrate, each of an electronic circuit, an etch stop layer, and a hinge base mounted on the substrate, and an electrode connected to the circuit. A hinge is mounted on the base and is made of a doped semiconductor. The hinge includes a vertical support that extends vertically from the base, and a horizontally-extending hinge tab contacts the vertical support. The device also includes a movable mirror and a mirror via that couples the mirror to the hinge tab. The mirror is electrostatically attracted to the electrode responsive to application of a voltage between the electrode and the mirror, and movement of the mirror changes a relative position between the hinge tab and the vertical support. A stopper is mounted on the substrate that mechanically stops the movement of the mirror before the mirror contacts the electrode or etch stop layer.