MEMS Actuator Edge Planarization via Thermal Diffusion
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Solution Overview
Problem
Existing actuators used in optical scanners, such as those formed using MEMS technology, suffer from stress concentration due to irregularities and corners on torsional bars, leading to reduced lifetime, and the insulating layers formed to address these issues do not effectively planarize or round edges, thereby limiting their effectiveness.
Innovation Solution
An actuator design featuring a silicon base with a movable portion, connection portions, and support portions, where an insulating layer is strategically applied on the base's surface to planarize and round edges, reducing stress concentration and extending the actuator's lifetime, and incorporating a conductive pattern on the insulating layer for insulation and light reflection prevention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating layer is formed on the side surfaces of the movable plate and torsional bars, then electrical insulation is achieved, but the irregular side surfaces cannot be fully planarized and corners cannot be fully rounded
Solution Approach 1:
The patent applies thermal treatment (silicon surface diffusion motion) BEFORE forming the insulating layer to planarize the side surfaces and round the corners. This preliminary action removes irregularities and corners that would otherwise prevent full planarization when the insulating layer is subsequently formed, thereby resolving the contradiction between achieving electrical insulation and maintaining surface planarity.
2Manufacturing precision
If thermal treatment is performed to planarize side surfaces and round corners, then stress concentration is reduced, but the insulating layer prevents full planarization and rounding
Solution Approach 1:
The patent performs thermal treatment (silicon surface diffusion motion) as a preliminary step before forming the insulating layer. This timing is critical because it allows the silicon surface to diffuse and planarize the side surfaces and round the corners without the insulating layer being present to obstruct the diffusion process, thereby achieving both surface planarity and stress concentration reduction.
3Ease of manufacture
If corners are left sharp for structural integrity, then manufacturing is simpler, but stress concentration occurs during oscillation reducing actuator lifetime
Solution Approach 1:
The patent changes the physical state and geometry of the silicon surface through thermal treatment (silicon surface diffusion motion), which causes the silicon atoms to diffuse and naturally round the corners. This parameter change in the silicon surface morphology eliminates sharp corners that cause stress concentration, thereby extending actuator lifetime while maintaining manufacturing simplicity as the rounding occurs automatically during the thermal process.
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 effectively planarizes and rounds edges, reducing stress concentration and prolonging the lifetime of the actuator and optical scanner, while also ensuring reliable insulation and minimizing stray light through the use of silicon oxide or nitride films and conductive materials like Ta.
Implementation Method 1
it is effective to perform a thermal treatment using silicon surface diffusion motion
Implementation Method 2
an insulating layer provided on a surface of the base... a conductive portion having conductivity and provided on the insulating layer
Data Source
AI summary
An actuator includes a base made of silicon and including a movable portion capable of oscillating around an oscillation axis, at least one connection portion extending from the movable portion, and a support portion that supports the connection portion, an insulating layer provided on a surface of the base, and a conductive portion having conductivity and provided on the insulating layer. In a plan view of the base viewed in a thickness direction of the base, the insulating layer is provided on portions other than an edge of the connection portion, an edge that connects an edge of the movable portion to the edge of the connection portion, and an edge that connects an edge of the support portion to the edge of the connection portion.