Retrograde Sidewall Etching for Optical Interconnect Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current optical signal processing circuits face challenges in achieving precise energy conversion and alignment between optical fibers and electrical circuitry, particularly in forming suitable angles on monocrystalline silicon substrates for efficient signal transmission and reflection.
Innovation Solution
The development of a method to create retrograde angled sidewalls on monocrystalline silicon substrates using anisotropic etching techniques, allowing for the formation of cavities with angles greater than 90°, such as 135°, which are used as mirrors for precise positioning and reflection of light beams, and the integration of these substrates into micro-electromechanical systems (MEMS) for enhanced optical interconnects and sensing applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional isotropic etching is used on monocrystalline silicon substrates, then the etching process is simple and fast, but the sidewall angles cannot achieve the precise retrograde angles (greater than 90°) required for efficient optical reflection and alignment
Solution Approach 1:
The patent changes the etching parameters by using anisotropic etching instead of isotropic etching, and by changing the crystallographic orientation of the silicon substrate from <100> to <110>. This parameter change enables the formation of retrograde sidewall angles greater than 90°, which are necessary for precise optical reflection and alignment in optical interconnect modules.
Solution Approach 2:
The patent employs a composite approach by combining specific crystallographic orientation (<110> silicon) with anisotropic etching processes to achieve the desired retrograde angles. This composite method of material selection and process combination enables precise angle control that neither approach could achieve alone.
2Reliability
If precise retrograde angled sidewalls are formed using anisotropic etching, then optical alignment and energy conversion efficiency are improved, but the etching process time and complexity increase
Solution Approach 1:
By changing to <110> oriented silicon and using anisotropic etching, the process achieves self-aligned retrograde walls that form naturally according to the crystallographic planes. This parameter change reduces the need for multiple iterative adjustment steps, thereby reducing overall process time despite the increased complexity of the etching chemistry itself.
Solution Approach 2:
The anisotropic etching process on <110> silicon automatically generates the retrograde sidewall angles through the inherent crystallographic structure. The etching process serves itself by using the material's own atomic structure to define the final geometry, eliminating the need for additional alignment and adjustment operations that would consume time.
3Ease of manufacture
If 45° micro-reflectors are used in optical interconnect modules, then fiber positioning is simplified, but the energy conversion efficiency and signal transmission quality are insufficient compared to retrograde angles
Solution Approach 1:
The patent changes the reflection surface angle from 45° to retrograde angles greater than 90°. This parameter change improves the coupling efficiency between optical fibers and the reflector surface, reducing power loss and improving signal transmission quality while maintaining ease of manufacture through the self-aligned etching process.
Solution Approach 2:
Instead of using acute angles (45°) that require precise external alignment, the patent inverts to using obtuse retrograde angles that naturally guide and align optical beams through their geometric configuration. This inversion leverages the geometry itself for alignment rather than requiring separate alignment mechanisms.
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 precise alignment and efficient energy conversion with reduced power losses, allowing for high-speed optical interconnects and improved sensing capabilities by utilizing the retrograde angled sidewalls for precise beam reflection and detection, enhancing the performance of optical and non-optical systems.
Implementation Method 1
The development of a method to create retrograde angled sidewalls on monocrystalline silicon substrates using anisotropic etching techniques
Implementation Method 2
anisotropic etching techniques, allowing for the formation of cavities with angles greater than 90°
Implementation Method 3
utilizing the retrograde angled sidewalls for precise beam reflection and detection
Implementation Method 4
retrograde angled sidewalls on monocrystalline silicon substrates... which are used as mirrors for precise positioning and reflection of light beams
Data Source
Figure 1~3
Figure 4
Figure 5A~7
AI summary
An interposer includes grooves (310) for waveguides 104 (e.g. optical fiber cables) coupled to a transducer (120). The grooves are formed by etching a cavity (410) in a substrate (130), filling the cavity with some layer (520), then etching the layer to form the grooves. The grooves can be formed in a separate structure which is then inserted into a cavity in an interposer having electrical circuitry for the transducer. The cavity has outwardly or inwardly sloped sidewalls which can serve as mirrors (144) or on which the mirrors are later formed. The substrate can be monocrystalline silicon, in which the inwardly sloped (retrograde) sidewalls are formed by a combination of different etches at least one of which is selective to certain crystal planes. Other features, including non-optical embodiments, are also provided.