Via Structure for Backside Routing in Layered MEMS Devices
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Solution Overview
Problem
Existing micro-electronic and micro-mechanic devices face challenges in closely spacing mirrors and other movable elements due to the interference caused by surface-routed electrical leads, which hinder efficient actuation and require additional space for wire-bonding, limiting the reduction of mirror dimensions.
Innovation Solution
The implementation of vias through wafers allows for the positioning of actuation electrodes underneath mirrors without disturbing other elements, enabling backside routing of leads within the wafer native material, using insulated conductive connections and plugs to maintain conductivity while preventing electrical coupling with adjacent layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If surface routing of electrical leads is used, then ease of manufacture is improved, but mirror spacing is reduced due to interference and additional space requirements
Solution Approach 1:
The patent transitions from two-dimensional surface routing to three-dimensional routing by extending leads through the substrate via vias. This allows leads to pass underneath mirrors in the vertical dimension, eliminating lateral interference and enabling closer mirror spacing while maintaining manufacturing feasibility through established via formation processes.
Solution Approach 2:
The patent introduces an insulating layer as an intermediary between the conductive leads and adjacent mirrors. This mediator prevents electrical interference and capacitive coupling between the leads and non-actuated mirrors, allowing surface routing to be used without the harmful interference that previously constrained mirror spacing.
2Ease of manufacture
If wire-bonding is performed on the same side as mirrors, then ease of manufacture is improved, but device dimensions are increased
Solution Approach 1:
The patent utilizes the vertical dimension by routing leads through the substrate thickness via vias to reach bond pads on the backside of the device. This removes wire-bonding operations from the front surface plane, eliminating the need for additional lateral space and enabling compact device footprints while maintaining standard wire-bonding manufacturing processes.
3Length of moving object
If electrical leads are routed beneath mirrors, then mirror spacing is improved, but electrical interference occurs with non-actuated mirrors
Solution Approach 1:
The patent employs an insulating layer as a protective intermediary positioned between the conductive leads passing through the substrate and the mirrors that should not be actuated. This insulation barrier prevents electrical field interference and capacitive coupling, allowing leads to be routed beneath mirrors without causing unwanted actuation or interference with non-actuated elements.
Solution Approach 2:
The patent applies insulation selectively in specific regions where leads pass near or beneath mirrors. Rather than insulating all leads uniformly, the insulating layer is positioned only where necessary to prevent interference with non-actuated mirrors, while maintaining electrical connectivity where needed for actuated mirrors. This localized approach enables close mirror spacing without unnecessary interference.
Data Source
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AI summary
The invention relates to a layered micro-electronic and/or micro-mechanic structure, comprising at least three alternating electrically conductive layers with insulating layers between the conductive layers. There is also provided a via in a first outer layer, said via comprising an insulated conductive connection made of wafer native material through the layer, an electrically conductive plug extending through the other layers and into said via in the first outer layer in order to provide conductivity through the layers, and an insulating enclosure surrounding said conductive plug in at least one selected layer of said other layers for insulating said plug from the material in said selected layer. It also relates to micro-electronic and/or micro-mechanic device comprising a movable member provided above a cavity such that it is movable in at least one direction. The device has a layered structure according to the invention. Methods of making such a layered MEMS structure is also provided.