Waveguide Facet Fabrication via Multi-Step Etching
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Solution Overview
Problem
Existing semiconductor waveguide fabrication techniques face challenges in achieving low roughness on facets and efficient die separation without damaging waveguide structures, which affects light coupling and scattering efficiency.
Innovation Solution
A method involving multiple etching processes to form waveguide facets and trenches on a substrate, using reactive ion etching and deep reactive ion etching to define waveguide structures and separate dice, while maintaining a smooth surface and minimizing damage to waveguide facets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple etching processes are used to define waveguide facets, then manufacturing precision of waveguide structures is improved, but process complexity increases
Solution Approach 1:
The etching process is divided into multiple sequential steps: first etching to define the waveguide structure and initial facet, then second etching to refine the facet surface. This segmentation allows each etching step to be optimized for its specific function, achieving mirror-smooth facets while managing process complexity through systematic breakdown of the fabrication sequence.
2Productivity
If deep etching is performed to separate dice, then die separation efficiency is improved, but risk of damaging waveguide structures increases
Solution Approach 1:
The waveguide facets and protective bridges are defined through preliminary etching steps before the final deep etching that separates the dice. This preliminary action creates a protective framework that guides the subsequent deep etching process, ensuring that the separation occurs cleanly without damaging the waveguide structures that were already formed.
Solution Approach 2:
Undersized bridges are created as intermediary structures that span between adjacent dice during the etching process. These bridges act as protective mediators that prevent the etching process from directly contacting and damaging the waveguide structures, while still allowing the deep etching to proceed for effective die separation.
3Productivity
If aggressive etching is used to remove material quickly, then productivity is improved, but surface roughness of facets increases
Solution Approach 1:
The material removal process is segmented into multiple etching passes rather than using a single aggressive etching step. The first etching removes the bulk material to define the waveguide structure, while subsequent etching steps progressively refine the facet surface. This segmentation enables controlled material removal that achieves both productivity and mirror-smooth surface finish.
Solution Approach 2:
The etching process uses partial action by performing multiple etching steps that remove material incrementally rather than all at once. Each etching step removes a portion of the material and leaves the facet slightly oversized, which is then refined in subsequent steps. This approach prevents the surface roughness that would result from a single excessive etching action while maintaining overall productivity.
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
The method effectively reduces light scattering and maximizes coupling efficiency by maintaining mirror-smooth waveguide facets and enabling precise separation of dice without damaging the waveguide structures, thereby improving the performance of semiconductor waveguides.
Implementation Method 1
performing a first etching process that etches a first layer of the substrate
Implementation Method 2
using reactive ion etching and deep reactive ion etching to define waveguide structures
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A fabrication method includes arranging a plurality of dice on a substrate and performing a first etching process that etches a first layer of the substrate at a boundary between adjacent dice on the substrate. The etching forms facets of one or more waveguides that are defined within the first layer, and the etching leaves a portion of the first layer in the boundary between the adjacent dice. The method continues with a second etching process that etches the portion of the first layer and a second layer beneath the portion of the first layer, the second etching process forming a trench in the boundary where the second layer has a different material than the first layer. The method also includes separating the dice from one another along the trench. A second, similar method includes separating the adjacent dice along a region displaced from the trench. A third method inlcudes the first etching process leaving behind bridge portions of the first layer in the boundary, and patterning polymer material over the bridge portions. A second etching process etches through a third thickness of a bulk portion of the substrate beneath a second layer, and through a second thickness of the second layer such that the dice are connected to a remainder of the substrate or to each other via the bridge portions and the patterned polymer material.