Reference Cavities for Passive Optical Alignment
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Solution Overview
Problem
Active alignment processes in opto-electronic assemblies are slow, expensive, and complex, while passive alignment methods add cost and complexity due to the need for alignment fiducials, making wafer level packaging inefficient as the size and complexity of opto-electronic assemblies increase.
Innovation Solution
The use of precision-created reference cavities on a substrate for passive optical alignment, where each optical component is placed within a cavity with a matching perimeter and right-angle corner, eliminating the need for alignment fiducials and allowing for efficient assembly by matching the component's footprint, and optionally incorporating grooves or ribs for adhesive placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If active alignment processes are used, then optical alignment precision is achieved, but assembly time and cost increase significantly
Solution Approach 1:
The patent implements preliminary action by pre-forming alignment fiducials on the substrate and optical components during fabrication, rather than performing alignment during assembly. These fiducials are created in advance using photolithography and etching processes, enabling passive alignment during assembly where the components self-align through the pre-formed fiducial features, eliminating the need for time-consuming active alignment procedures.
2Productivity
If passive alignment with fiducials is used, then assembly time is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The patent applies universality by designing fiducials that serve multiple functions: they provide optical alignment references, define component positioning, and can be integrated into the substrate and component fabrication processes. The fiducial structures are designed to be compatible with standard semiconductor manufacturing processes, allowing them to be formed as part of the normal fabrication flow rather than requiring separate specialized steps.
3Productivity
If wafer level packaging is used, then assembly efficiency improves, but alignment complexity increases with larger assemblies
Solution Approach 1:
The patent implements segmentation by dividing the large wafer-level assembly into multiple smaller regions, each with its own set of alignment fiducials. This allows independent alignment control for each region while maintaining overall assembly efficiency. The wafer is segmented into multiple chip sites, each with locally defined fiducials that can be aligned independently, reducing the complexity of aligning large-scale assemblies.
Data Source
AI summary
An arrangement for providing passive alignment of optical components on a common substrate uses a set of reference cavities, where each optical device is positioned within a separate reference cavity. The reference cavities are formed to have a predetermined depth, with perimeters slightly larger than the footprint of their associated optical components. The reference cavity includes at least one right-angle corner that is used as a registration corner against which a right-angle corner of an associated optical component is positioned. The placement of each optical component in its own reference cavity allows for passive optical alignment to be achieved by placing each component against its predefined registration corner.