Blazed Grating Fabrication Using Spacers and Ion Beam Etching
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Solution Overview
Problem
Blazed gratings are difficult to manufacture using traditional patterning methods, which hinders their application in augmented reality waveguides for high diffraction efficiency.
Innovation Solution
A method involving the deposition of a mandrel over a substrate, followed by etching to form trenches, deposition of a spacer material, and subsequent ion beam etching to create blazed gratings, with optional additional mandrel layers and etching steps to achieve precise control over blaze angle and critical dimension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional patterning methods are used to manufacture blazed gratings, then the manufacturing process is simple, but the manufacturing precision and diffraction efficiency are insufficient
Solution Approach 1:
The manufacturing process is divided into multiple sequential steps: depositing a mandrel layer, forming trenches, depositing spacer material, removing the mandrel, and performing ion beam etching. This segmentation allows each step to be optimized independently, achieving high precision blazed gratings while managing overall process complexity through systematic breakdown of the manufacturing sequence.
Solution Approach 2:
A mandrel layer is deposited and patterned in advance to define the trench locations and dimensions before the actual grating formation. This preliminary structuring enables precise control of the subsequent spacer deposition and ion beam etching processes, ensuring high manufacturing precision for the final blazed grating structure.
2Reliability
If ion beam etching is used to form blazed gratings, then the diffraction efficiency increases, but the manufacturing time and process steps increase
Solution Approach 1:
The ion beam etching process is performed continuously on the spacer material after it has been deposited and patterned, maintaining the precise geometric relationships established in previous steps. This continuous etching action ensures high diffraction efficiency by creating accurate blazed grating profiles without requiring intermediate interruptions or repositioning steps.
Solution Approach 2:
A spacer material is introduced as an intermediary layer between the mandrel and the final grating structure. The spacer material is deposited, patterned, and then etched to form the blazed grating profile. This intermediary approach allows the ion beam etching to work on a dedicated layer, improving diffraction efficiency while containing the time investment to a specific process module rather than the entire manufacturing sequence.
3Measurement precision
If multiple mandrel layers are deposited, then the critical dimension control improves, but the device complexity increases
Solution Approach 1:
Instead of increasing lateral resolution through more complex lithography, the patent uses vertical stacking of multiple mandrel layers to achieve precise critical dimension control. Each mandrel layer is deposited and patterned at a different height, allowing independent optimization of their respective dimensions. The final grating structure integrates these vertically-stacked features, achieving high measurement precision through dimensional transition from 2D to 3D space.
Solution Approach 2:
Multiple mandrel layers are deposited in a nested sequence, where each subsequent mandrel layer is formed within the structural context of the previous layers. The first mandrel defines initial trenches, the second mandrel is deposited over and patterned relative to the first, creating a nested hierarchical structure. This nesting approach enables precise critical dimension control through cumulative dimensional control across layers while organizing process complexity in a manageable sequential framework.
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
Enables the formation of blazed gratings with reduced critical dimensions and increased process control, enhancing optical efficiency by increasing the intensity of targeted diffraction orders and reducing other orders, thus improving augmented reality display performance.
Implementation Method 1
The mandrel is etched using ion beam etching (IBE). The mandrel and the substrate are etched to form a blazed grating.
Data Source
AI summary
Aspects of the present disclosure includes methods of forming a waveguide. The method of forming a waveguide includes depositing a mandrel disposed over a substrate. Portions of the mandrel are etched to form a trench. A spacer material is deposited over the mandrel and the substrate. The spacer material is etched to form a spacer in the trench. The mandrel is etched using ion beam etching (IBE). The mandrel and the substrate are etched to form a blazed grating. The spacer is removed.