Photonics Chip Reference Markers for Edge Coupler Cavity Metrology
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Solution Overview
Problem
Existing methods for measuring cavity dimensions in photonics chips are inefficient, particularly due to the difficulty in measuring the width dimension of the cavity proximate to the tip of the inverse taper, which leads to misalignment between the edge coupler and the output of the light source, causing inefficiency in the photonics chip.
Innovation Solution
The implementation of a structure comprising a dielectric layer with a cavity that includes a fill region positioned on the first dielectric layer, where the cavity extends from the first edge of the semiconductor substrate, and the perimeter of the first reference marker, which overlaps with a portion of the semiconductor substrate, and the perimeter of the semiconductor substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the cavity is buried beneath several microns of dielectric material, then the structure is more compact and integrated, but the measurement precision of cavity dimensions deteriorates
Solution Approach 1:
The patent introduces reference markers as intermediary features that can be measured with standard metrology tools. These markers are positioned at known distances from the cavity, allowing indirect measurement of cavity dimensions through the markers rather than direct measurement of the buried cavity itself. This mediator approach resolves the contradiction by enabling precise measurement despite the cavity being buried beneath dielectric material.
Solution Approach 2:
The patent creates a measurement copy by forming reference markers that replicate the positional information of the cavity boundaries. Instead of measuring the actual buried cavity directly, the reference markers serve as measurable copies or proxies that contain the same dimensional information, allowing precise measurement without exposing the original cavity.
2Ease of manufacture
If the cavity dimensions are difficult to measure, then the manufacturing process is simpler, but the alignment precision between edge coupler and light source deteriorates
Solution Approach 1:
The patent applies preliminary action by forming reference markers during the same fabrication process as the cavity, before the cavity dimensions need to be measured for alignment. The reference markers are created in advance at positions that encode the cavity boundary information, so that when measurement is needed, the markers are already in place to guide precise alignment of the edge coupler and light source.
Solution Approach 2:
The reference markers serve as intermediary reference features that bridge the gap between the easily-formed cavity and the precision alignment requirement. The markers are simple to manufacture like the cavity, but they provide the measurement precision needed for alignment, thus resolving the contradiction between manufacturing simplicity and alignment precision.
3Device complexity
If no reference markers are provided, then the device structure is simpler, but the measurement capability of cavity dimensions deteriorates
Solution Approach 1:
The reference markers act as intermediary measurement aids that make the measurement process feasible. Without these markers, direct measurement of the buried cavity would be extremely difficult or impossible with standard tools. The markers provide observable features at the surface that correlate to the buried cavity dimensions, enabling measurement without adding significant structural complexity.
Solution Approach 2:
The reference markers create a measurable surface representation of the buried cavity's dimensional information. By copying the positional and dimensional relationships to the surface through the marker formation process, the patent enables measurement capability without requiring the cavity itself to be accessible or complex in structure.
Data Source
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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.