Tapered SOI Optical Waveguide Core Layer Constriction
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Solution Overview
Problem
Conventional methods for producing SOI optical waveguides with spot size conversion are complex due to separate processes for constraining waveguide width and thickness, leading to increased optical propagation losses.
Innovation Solution
A method to simultaneously constrict both the width and thickness of the SOI optical waveguide core layer using a single process, employing a silicon nitride film as a mask for LOCOS oxidation, allowing for a tapered waveguide structure that reduces optical losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate processes are used to constrict waveguide width and thickness, then manufacturing precision can be maintained, but device complexity and production time increase
Solution Approach 1:
The patent combines the width constriction and thickness reduction processes into a single integrated process. The mask layer is patterned with a tapered profile that simultaneously defines both the width and thickness of the waveguide core layer, eliminating the need for separate etching and thinning processes.
Solution Approach 2:
The mask layer is formed with a predetermined tapered profile before the constriction process. This preliminary structuring of the mask layer with the desired final waveguide geometry allows both width and thickness to be controlled in one subsequent processing step.
2Manufacturing precision
If multiple processes are used for width and thickness constriction, then manufacturing precision can be maintained, but productivity decreases
Solution Approach 1:
The patent merges multiple constriction operations into a single process step by using a pre-patterned mask layer with tapered geometry, thereby reducing the total number of processing steps and increasing production efficiency.
Solution Approach 2:
The mask layer is prepared in advance with the exact tapered profile needed, so that the subsequent single processing step can simultaneously achieve both width and thickness constriction without requiring multiple sequential operations.
3Manufacturing precision
If etching process is used to constrict waveguide width, then manufacturing precision can be achieved, but optical propagation losses increase
Solution Approach 1:
The patent introduces a mask layer as an intermediary element that defines the waveguide geometry. Instead of directly etching the waveguide core to constrict its width, the mask layer with tapered profile is used to guide the constriction process, reducing direct damage to the waveguide core and minimizing optical propagation losses.
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 simplifies the production process, reduces optical coupling losses, and minimizes propagation losses by forming a tapered waveguide without damaging the silicon layer, enabling low-cost, high-yield spot size conversion.
Implementation Method 1
the width of the first core layer is defined based on the width of an unoxidized semiconductor material sandwiched between oxide films the parts of which are thermally oxidized; the thickness of the first core layer is defined based on the thickness of an unoxidized semiconductor material sandwiched between the first clad layer and an oxide film the part of which is thermally oxidized
Data Source
AI summary
Provided are an optical waveguide and a production method thereof which can constrict both the width and thickness of the SOI optical waveguide core layer in the same process and at the same time, simplify production process, and reduce optical losses. An optical waveguide includes a first clad layer formed on a semiconductor substrate; a first core layer formed on the upper side of the first clad layer with the use of a semiconductor material the refractive index of which is higher than that of the first clad layer; and a second clad layer formed on the upper side of the first core layer with the use of a material the refractive index of which is lower than that of the first core layer. The width of the first core layer is defined based on the width of an unoxidized semiconductor material sandwiched between oxide films the parts of which are thermally oxidized. The thickness of the first core layer is defined based on the thickness of an unoxidized semiconductor material sandwiched between the first clad layer and an oxide film the part of which is thermally oxidized. At least the input/output portion of the optical waveguide has a tapered waveguide portion where the width and thickness of the first core layer monotonically decreases or increases with respect to the propagation direction of light.