Angled Grating Etching with Ion Beam Slant and Depth Control
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Solution Overview
Problem
Conventional augmented reality waveguide combiners face challenges in controlling light intensity and achieving optimal light in-coupling and out-coupling due to limitations in grating designs, particularly with varying slant angles and depth gradients that are not aligned with the grating vector.
Innovation Solution
The method involves etching a hardmask layer over a grating material layer on a substrate to form gratings with specific shape and grating vectors by adjusting ion beam angles and modulating process parameters, such as duty cycle, to create gratings with controlled slant angles and depth gradients, allowing for improved optical uniformity and alignment with the grating vector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional grating designs are used in augmented waveguide combiners, then the device structure is simple, but the light intensity control is inadequate and optical uniformity is poor
Solution Approach 1:
The patent applies dynamics by making the ion beam angle adjustable during the etching process. The system transitions from a fixed-angle etching approach to a dynamic approach where the ion beam angle can be changed to match different grating slant angles, enabling precise control of grating geometry while maintaining process flexibility
Solution Approach 2:
The patent implements parameter changes by varying the ion beam angle as a controllable parameter during etching. By adjusting this parameter to match the desired grating slant angle, the system achieves precise control over grating formation, directly addressing the need for manufacturing precision in grating slant angles
2Reliability
If gratings with different slant angles are used to control light in-coupling and out-coupling, then light control improves, but the manufacturing process becomes more complex
Solution Approach 1:
The system uses dynamic adjustment of the ion beam angle to accommodate different grating slant angle requirements. This allows the same etching tool to manufacture gratings with varying slant angles by simply changing the beam angle parameter, maintaining ease of manufacture while achieving reliable light control
Solution Approach 2:
The etching system achieves multi-functionality by being capable of forming gratings with different slant angles using a single tool and process. The ion beam angle adjustment mechanism allows one system to perform multiple grating fabrication tasks, improving both light control reliability and manufacturing ease
3Stability of the object's composition
If the ion beam angle is adjusted to match the grating slant angle, then optical uniformity improves, but the etching process complexity increases
Solution Approach 1:
The patent uses parameter changes by directly matching the ion beam angle parameter to the grating slant angle parameter. This straightforward parameter alignment simplifies the relationship between process settings and output quality, achieving optical uniformity without excessive system complexity
Solution Approach 2:
The patent replaces complex mechanical alignment systems with a more straightforward ion beam angle adjustment mechanism. By controlling the beam angle directly rather than using complex mechanical positioning of the substrate or tool, the system achieves optical uniformity with reduced overall system complexity
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 formation of gratings with precise slant angles and depth gradients, enhancing light control and optical uniformity in augmented reality devices, thereby improving the display of virtual images in augmented reality environments.
Implementation Method 1
etching a hardmask layer to form a plurality of openings, the hardmask layer being disposed over a grating material layer that is disposed on a substrate and forming a first grating in the grating material layer through the plurality of openings of the hardmask layer
Implementation Method 2
depositing an etch stop layer in the first feature, depositing a second grating material layer on the etch stop layer, and depositing a hardmask layer on the second grating material layer
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
Systems and methods discussed herein can be used to form gratings at various slant angles across a grating material on a single substrate by determining an ion beam angle and changing the angle of an ion beam among and between ion beam angles to form gratings with varying angles and cross-sectional geometries. The substrate can be rotated around a central axis, and one or more process parameters, such as a duty cycle of the ion beam, can be modulated to form a grating with a depth gradient.