MEMS Micromirror Vertical Actuation for Compact Optical Resolution
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Solution Overview
Problem
MEMS micromirrors with increasing optical resolution require larger reflecting surfaces, leading to undesirable increases in device dimensions due to the space occupied by actuation elements, position sensors, and other driving and control components.
Innovation Solution
A micro-electro-mechanical device with a movable structure where actuation and sensing elements are formed within a die, allowing the movable part to rotate about a vertical axis, with elastic elements connecting the movable and fixed parts, thereby maximizing the reflecting surface area while minimizing overall device dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reflecting surface area is increased to improve optical resolution, then the optical resolution is improved, but the overall device dimensions increase
Solution Approach 1:
The patent positions actuation and sensing elements in the vertical dimension (below and above the reflecting surface plane) rather than in the planar dimension. The actuation structure is formed below the reflecting surface and the sensing structure is formed above it, allowing the reflecting surface area to be maximized without increasing device footprint area.
Solution Approach 2:
The actuation structure and sensing structure are nested in the vertical space around the reflecting surface. The actuation structure is embedded below the reflecting surface while the sensing structure is positioned above it, creating a compact vertical stacking arrangement that maximizes the use of three-dimensional space.
2Measurement precision
If actuation and sensing elements are added to control mirror rotation, then the control precision is improved, but the device complexity increases
Solution Approach 1:
The actuation structure and sensing structure are integrated into a single die together with the mirror structure. All three components (mirror, actuation, sensing) are formed in the same semiconductor substrate using a unified manufacturing process, reducing assembly complexity and improving integration.
Solution Approach 2:
The patent uses electrostatic actuation and capacitive sensing instead of mechanical systems. The actuation structure uses electrostatic forces to rotate the mirror, and the sensing structure uses capacitive measurements to detect angular position, eliminating the need for mechanical contacts and complex mechanical sensing mechanisms.
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 the formation of MEMS devices with reduced dimensions, allowing for larger reflecting surfaces without increasing the device's overall size, thus maintaining compactness and improving mechanical yield.
Implementation Method 1
a first pair of arms (12) having elastically deformable portions, which form first torsion springs
Implementation Method 2
A first actuation structure (18A) (shown only schematically and of an electrostatic, magnetic, or piezoelectric type) is coupled to the first arms (12) or to the suspended region (11) and is configured to cause a rotation actuation movement
Implementation Method 3
A first actuation structure (18A) (shown only schematically and of an electrostatic, magnetic, or piezoelectric type) is coupled to the first arms (12) or to the suspended region (11) and is configured to cause a rotation actuation movement
Implementation Method 4
A first actuation structure (18A) (shown only schematically and of an electrostatic, magnetic, or piezoelectric type) is coupled to the first arms (12) or to the suspended region (11) and is configured to cause a rotation actuation movement
Data Source
Figure 1~3
Figure 4~5
Figure 6A~6B
AI summary
The micro-electro-mechanical device (20) is formed in a first wafer (40) overlying and bonded to a second wafer (70). A fixed part (91), a movable part (92), and elastic elements, elastically coupling the movable part and the fixed part, are formed in the first wafer. The movable part carries actuation elements (60) configured to control a relative movement, such as a rotation, of the movable part with respect to the fixed part. The second wafer is bonded to the first wafer through projections (66) of the first wafer, formed by selectively removing part of a semiconductor layer (43). The composite wafer formed by the first and second wafers is cut to form a plurality of MEMS devices.