Ion Implantation for Slanted Surface-Relief Grating Fabrication
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Solution Overview
Problem
Existing techniques face challenges in fabricating slanted structures with high precision and accuracy, particularly in materials with high refractive indices, due to issues like shadowing effects during etching and undesirable changes in material properties from ion implantation, which affect the performance of waveguide-based artificial reality display systems.
Innovation Solution
A method involving ion implantation to modify the material phase and subsequent selective etching processes, which includes oxidation and reduction steps to achieve desired slant angles, depths, and duty cycles in surface-relief gratings, while alleviating the negative effects of ion implantation on optical quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ion implantation is used to etch surface-relief structures, then the etching capability is improved, but optical loss increases due to material property changes
Solution Approach 1:
The patent extracts and removes the ion-implanted regions from the material layer through selective etching. By taking out the damaged regions that cause optical loss while retaining the desired slanted structure geometry, the method resolves the contradiction between achieving etching capability and minimizing optical loss.
Solution Approach 2:
The patent applies local quality by creating regions with different oxidation rates through ion implantation. The ion-implanted regions have modified properties (higher oxidation rate) compared to non-implanted regions, enabling selective removal of specific areas while preserving others, thus achieving both etching capability and optical quality.
2Manufacturing precision
If ion implantation is used to create slanted structures, then desired slant angles and depths are achieved, but material defects increase
Solution Approach 1:
The patent removes the defective ion-implanted regions through selective oxidation and etching. By extracting these damaged areas, the method maintains the precise slanted geometry achieved during implantation while eliminating the associated material defects and improving overall reliability.
Solution Approach 2:
The patent changes the chemical and physical parameters of the ion-implanted regions through oxidation processes. This parameter change enables differentiation between implanted and non-implanted regions, allowing selective removal of defective areas while preserving the structurally sound portions.
3Manufacturing precision
If shadowing effects are reduced during etching, then etching uniformity is improved, but process complexity increases
Solution Approach 1:
The patent performs preliminary ion implantation to modify material properties before the main etching process. This preliminary action creates regions with different oxidation rates, which then guide the subsequent selective etching process, achieving uniform results without requiring complex real-time shadowing control.
Solution Approach 2:
The patent introduces oxidation as an intermediary process between ion implantation and final etching. This intermediary step converts the ion-implanted regions into oxides with distinct etch characteristics, enabling uniform selective removal while simplifying the overall process control compared to direct shadowing-based methods.
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 slanted gratings with improved optical performance, reduced optical loss, and increased brightness efficiency in waveguide-based displays by precisely controlling the etch depth and duty cycle, addressing the limitations of previous methods.
Implementation Method 1
implanting ions into a plurality of regions of the material layer using the mask layer and an ion beam at a slant angle equal to or greater than 0°
Implementation Method 2
an oxidation process may be performed to further modify the ion implanted region to form oxides that may be more selectively etched
Data Source
AI summary
A method of fabricating a surface-relief structure in a material layer (e.g., including dielectric or semiconductor material) includes forming a mask layer on the material layer, implanting ions (e.g., using ion beam implantation or ion beam etching) into a plurality of regions of the material layer using the mask layer and an ion beam having a slant angle equal to or greater than 0° (e.g., greater than about 30° or about 45°) with respect to a surface normal direction of the material layer to increase the oxidation rate (or reduction rate) of the plurality of regions of the material layer, selectively oxidizing (or reducing) the plurality of regions of the material layer that include implanted ions, and selectively etching the oxidized or reduced materials in the plurality of regions of the material layer to form the surface-relief structure in the material layer.