Silicon Photonic Trench Depth Control Using Selective Etch Layers
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Solution Overview
Problem
Existing technologies face challenges in fabricating Silicon photonic integrated circuits with trenches of varying depths, particularly due to limitations in etching rate selectivity and the use of photoresist, which can restrict the depth of shallow trenches and lead to uneven deposition and stripping issues.
Innovation Solution
The use of etching rate selectivity techniques, which exploit the differential etch rates between Silicon and Silicon dioxide, allows for the simultaneous etching of trenches with different depths. This method involves depositing a thin slow-etch layer over shallow trench regions and etching both shallow and deep trenches simultaneously, ensuring precise control over trench depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photoresist is used to define trench regions during etching, then the etching process can be controlled, but the depth of shallow trenches is restricted and uneven deposition and stripping issues occur
Solution Approach 1:
The patent extracts and removes the photoresist material after it has served its purpose of defining trench regions during etching. By taking out the photoresist after use, the process eliminates the limitations imposed by photoresist thickness on trench depth while maintaining the benefits of controlled etching during the process.
Solution Approach 2:
The patent applies a slow-etch layer preliminarily over the substrate before the main etching process. This preliminary layer is designed to etch at a different rate than the underlying substrate, allowing deep trenches to be formed while protecting regions where shallow trenches are desired. The slow-etch layer acts as a depth-control mechanism that eliminates photoresist limitations.
2Manufacturing precision
If trenches of varying depths are fabricated using traditional methods, then shallow trenches can be formed, but the depth is restricted by photoresist thickness
Solution Approach 1:
The patent applies local quality by depositing a slow-etch layer selectively over specific regions of the substrate. This creates spatial variation in etching characteristics: regions with the slow-etch layer produce shallow trenches, while regions without it produce deep trenches. This local differentiation enables precise control over trench depths across different areas of the substrate.
Solution Approach 2:
The patent changes the etching parameter by introducing a material with different etching characteristics (the slow-etch layer). By altering the etching rate parameter locally through material selection and thickness control, the process achieves variable trench depths without being constrained by photoresist thickness, thereby expanding the adaptable depth range.
3Productivity
If simultaneous etching of multiple trenches is performed, then productivity is improved, but control over individual trench depths becomes difficult
Solution Approach 1:
The slow-etch layer serves as an intermediary material between the etching tool and the substrate. During simultaneous etching of multiple trenches, this intermediary layer mediates the etching process by providing different etching rates in different regions. This allows individual trench depth control to be maintained even while multiple trenches are etched simultaneously, as the slow-etch layer locally modulates the etching rate.
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 approach enables the fabrication of Silicon photonic integrated circuits with trenches of precise and varying depths, overcoming the limitations of traditional methods and ensuring efficient light coupling and integration of diverse optical components.
Implementation Method 1
exploit the differential etch rates between Silicon and Silicon dioxide, allows for the simultaneous etching of trenches with different depths
Data Source
AI summary
One or more photonic structures are formed within one or more layers over a surface of a substrate, and multiple trenches are formed through the one or more layers housing devices coupled to one or more of the photonic structures. The trenches may include: a first trench that has a bottom surface within the substrate that has a first surface topology characterized by a first surface roughness at a first depth within the substrate relative to the surface of the substrate, and a second trench that has a bottom surface within the substrate that has a second surface topology characterized by a second surface roughness at a second depth within the substrate relative to the surface of the substrate. The first surface roughness may be greater than the second surface roughness, and the second depth may be greater than the first depth.