MEMS Actuation Coil Uniformity via Dummy Biasing
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Solution Overview
Problem
MEMS devices with electromagnetic actuation suffer from non-uniform coil growth, leading to increased current passage resistance and dissipation due to thickness unevenness in the actuation coil, which becomes more pronounced with larger dimensions and greater number of turns.
Innovation Solution
Incorporating a dummy biasing structure adjacent to the actuation coil's intermediate turn, electrically coupled to the end turns, to maintain uniform galvanic growth by ensuring consistent potential across the coil during galvanic growth, thereby reducing thickness variations and improving coil uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the actuation coil is made with larger dimensions and greater number of turns to improve actuation performance, then the electromagnetic force increases, but the coil thickness becomes non-uniform during galvanic growth, leading to increased current passage resistance and energy dissipation
Solution Approach 1:
The patent introduces a dummy biasing structure electrically connected to intermediate turns of the coil to create equipotential regions during galvanic growth. This ensures uniform potential distribution across the entire coil length, preventing non-uniform thickness variations that would otherwise occur in larger coils with more turns, thereby maintaining both manufacturing precision and electrical performance
Solution Approach 2:
The dummy biasing structure acts as an intermediary element that mediates the electrical connection between different sections of the coil during manufacturing. By introducing this intermediate structure, the patent achieves uniform galvanic deposition across the entire coil while maintaining the ability to use larger dimensions and greater number of turns for improved actuation force
2Area of stationary object
If the coil thickness is reduced to minimize area consumption, then the device meets stringent area requirements, but the current passage resistance increases and energy dissipation worsens
Solution Approach 1:
By implementing equipotential regions through the dummy biasing structure, the patent enables more efficient current distribution throughout the coil. This allows for optimized coil design where the thickness can be minimized for area consumption while the uniform potential distribution ensures lower effective resistance and reduced energy dissipation
3Power
If the coil dimensions are increased to improve actuation performance, then the electromagnetic force increases, but the galvanic growth becomes non-uniform with thickness variations becoming more pronounced
Solution Approach 1:
The dummy biasing structure creates equipotential regions that stabilize the electrical potential distribution during galvanic growth. This allows the coil to be manufactured with larger dimensions and greater number of turns while maintaining uniform thickness consistency, as the equipotential conditions prevent the non-uniform growth that would otherwise occur in larger structures
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 dummy biasing structure ensures uniform thickness of the coil turns, reducing current passage resistance and enhancing operational efficiency while maintaining manufacturing process simplicity and cost-effectiveness.
Implementation Method 1
MEMS device having a tiltable suspended structure controlled by electromagnetic actuation
Implementation Method 2
maintain uniform galvanic growth by ensuring consistent potential across the coil during galvanic growth
Data Source
AI summary
A MEMS device is obtained by forming a temporary biasing structure on a semiconductor body, and forming an actuation coil on the semiconductor body, the actuation coil having at least one first end turn, one second end turn and an intermediate turn arranged between the first and the second end turns and electrically coupled to the first end turn through the temporary biasing structure. In this way, the intermediate turn is biased at approximately the same potential as the first end turn during galvanic growth, and, at the end of growth, the actuation coil has an approximately uniform thickness. At the end of galvanic growth, portions of the temporary biasing structure are selectively removed to electrically separate the first end turn from the intermediate turn and from a dummy biasing region adjacent to the first end turn.