Edge Coupler Reference Markers for Buried Cavity Measurement
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Solution Overview
Problem
The difficulty in measuring the dimensions of cavities adjacent to an edge coupler in photonics chips, particularly the width dimension proximate to the tip of the inverse taper, due to the cavity being buried beneath dielectric material, leads to misalignment issues between the edge coupler and the light source.
Innovation Solution
A structure is developed with a semiconductor substrate containing a cavity, a dielectric layer, and an edge coupler, featuring a fill region with reference markers surrounded by fill features that provide optical contrast for precise metrology, allowing accurate measurement of cavity dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cavity is formed in the semiconductor substrate and covered with dielectric material, then the light source can be properly positioned and protected, but the cavity dimensions become difficult to measure with metrology tools
Solution Approach 1:
The patent introduces reference markers as intermediary features that are positioned in known locations relative to the cavity. These markers serve as mediators between the measurement system and the cavity, allowing indirect measurement of cavity dimensions through the markers rather than direct measurement of the buried cavity itself.
Solution Approach 2:
The patent creates a surface-level representation or copy of the cavity's positional information through reference markers. The markers replicate the spatial relationship information of the cavity at a location that is accessible to metrology tools, enabling measurement without directly accessing the buried cavity.
2Device complexity
If the cavity width dimension is difficult to measure, then manufacturing complexity is reduced, but misalignment between the edge coupler and light source occurs
Solution Approach 1:
The reference markers act as intermediary reference points that simplify the measurement process. Instead of requiring complex direct measurement of the buried cavity, the system uses the markers as intermediaries to determine cavity position and dimensions, thereby reducing measurement complexity while maintaining alignment precision.
Solution Approach 2:
The reference markers are formed during the fabrication process before final assembly, establishing known reference positions in advance. This preliminary action of creating measurement references during manufacturing enables precise alignment to be achieved without requiring complex post-fabrication measurement systems.
Data Source
AI summary
Structures including a cavity adjacent to an edge coupler and methods of forming such structures. The structure comprises a semiconductor substrate including a cavity with a sidewall, a dielectric layer on the semiconductor substrate, and an edge coupler on the dielectric layer. The structure further comprises a fill region including a plurality of fill features adjacent to the edge coupler. The fill region includes a reference marker at least partially surrounded by the plurality of fill features, and the reference marker has a perimeter that surrounds a surface area of the dielectric layer, and the surface area overlaps with a portion of the sidewall of the cavity.