MEMS Interference Filter Groove Segmentation for Etchant Flow
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Solution Overview
Problem
In wavelength variable interference filters, the formation of grooves through etching often results in insufficient thinness of the flexible portion, leading to inadequate deflection and tilting of the movable substrate, which compromises the spectral performance and connection reliability.
Innovation Solution
The introduction of a second groove with a larger area than the first groove, connected to it, allows for enhanced etchant circulation during wet etching, ensuring the first groove's bottom is sufficiently thin, minimizing substrate deflection and tilting, and maintaining spectral performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a groove is formed through etching in the movable substrate, then the flexible portion becomes thinner and deflection improves, but unless the groove area is sufficiently large in plan view, the etchant cannot flow to the deep part of the groove, making it difficult to make the thin portion sufficiently thin
Solution Approach 1:
The groove is divided into a first groove (deeper, narrower) and a second groove (shallower, wider) that are connected. The second groove with larger area allows etchant to flow in and reach the deep part of the first groove, enabling the flexible portion to be made sufficiently thin while maintaining ease of manufacture through enhanced etchant circulation.
2Stability of the object's composition
If the thin portion is not made sufficiently thin, then deflection of the thin portion becomes insufficient, but making it thinner requires larger groove area which increases device complexity
Solution Approach 1:
The groove structure is segmented into two connected grooves with different characteristics. The first groove provides the necessary depth for sufficient thinness and deflection, while the second groove provides larger area for etchant flow. This segmentation achieves the desired parallelism without requiring a single overly complex groove structure.
3Reliability
If the movable substrate deflects or tilts, then connection reliability between electrodes deteriorates, but preventing this requires sufficient thinness of the flexible portion which is difficult to achieve with conventional etching
Solution Approach 1:
The segmented groove structure with a first and second connected groove enables the flexible portion to be made sufficiently thin, ensuring proper deflection and maintaining connection reliability between electrodes. The second groove's larger area ensures adequate etchant circulation to achieve the required thickness precision.
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
This configuration ensures reliable contact pressure and spectral performance by ensuring the first groove's depth is adequately secured, reducing substrate deflection and maintaining spectral accuracy.
Implementation Method 1
a first groove 520 and a second groove 522 which are connected to each other are simultaneously formed through wet etching
Implementation Method 2
the thin portion is elastically deformed, and thus contact pressure of the extraction electrode and the conduction electrode improves so that connection reliability is ensured
Data Source
AI summary
A wavelength variable interference filter includes a fixed substrate, a movable substrate that faces the fixed substrate, a pair of reflective films, a fixed extraction electrode provided on the fixed substrate, and a movable connection electrode that is provided on the movable substrate and is in contact with the fixed extraction electrode at a connection position, in which the movable substrate includes a first groove that is provided at the connection position in a plan view in which the fixed substrate and the movable substrate are viewed from a substrate thickness direction, and a second groove that has a larger area than an area of the first groove in the plan view and is connected to the first groove.