Faraday Cage Plasma Etching With Shutter Control
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Solution Overview
Problem
Plasma etching using a Faraday cage faces challenges in achieving uniformity and precision, particularly in forming microstructures with varying depth gradients, leading to irregular etching areas and the formation of needle-shaped structures that affect image quality in wearable devices like virtual and augmented reality devices.
Innovation Solution
A plasma etching method employing a Faraday cage with a metal mask and a shutter to control the etching process, allowing for the formation of groove patterns with specific depth gradients by shielding parts of the mesh portion, thereby controlling the etching rate and reducing needle-shaped structure generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If plasma etching is performed using a Faraday cage without additional shielding, then the etching process can be conducted with a simple structure, but the etching uniformity deteriorates and needle-shaped structures form on the substrate
Solution Approach 1:
The Faraday cage structure is segmented by dividing the mesh portion into multiple regions (first mesh region and second mesh region) with different mesh densities. The first mesh region has a first mesh density while the second mesh region has a second mesh density different from the first, allowing different etching rates in different areas to achieve uniform etching across the substrate
Solution Approach 2:
Different regions of the Faraday cage are given different local properties through varying mesh densities. The first mesh region and second mesh region have distinct mesh densities tailored to produce specific etching rates in their respective areas, enabling precise control over etching uniformity and preventing needle-shaped structure formation
2Manufacturing precision
If the mesh density is increased to improve etching control, then the etching precision improves, but the device complexity increases
Solution Approach 1:
Rather than uniformly increasing mesh density across the entire Faraday cage, the structure is segmented into regions with different mesh densities. This allows precise etching control only where needed while maintaining simpler structure in other areas, thus improving etching precision without proportionally increasing overall device complexity
Solution Approach 2:
High mesh density is applied locally only in specific regions where precise etching control is required, while other regions maintain lower mesh density. This localized approach achieves the necessary etching precision without unnecessarily complicating the overall device structure
3Device complexity
If a single mesh density is used throughout the Faraday cage, then the device structure remains simple, but the ability to form groove patterns with varying depth gradients is limited
Solution Approach 1:
The Faraday cage is divided into multiple mesh regions with different densities, enabling the formation of groove patterns with varying depth gradients. Each region's specific mesh density can be optimized for creating particular pattern features, greatly enhancing the device's versatility in pattern formation
Solution Approach 2:
Different local regions of the Faraday cage are equipped with different mesh densities to create specific etching characteristics in each area. This allows the device to form diverse groove patterns with different depth gradients simultaneously, significantly improving adaptability while maintaining reasonable structural 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 method enables the precise formation of groove patterns with varying depth gradients, improving etching uniformity and reducing needle-shaped structures, resulting in enhanced image quality and accuracy for diffraction grating light guide plates used in wearable devices.
Implementation Method 1
providing a substrate for etching in which a metal mask having an opening pattern portion is provided on one surface in a Faraday cage provided with a mesh portion on an upper surface
Implementation Method 2
a first patterning step of forming a first pattern area on the substrate for etching by using plasma etching
Data Source
AI summary
A plasma etching method using a Faraday cage, including: providing an etch substrate in a Faraday cage, where the etch substrate includes a metal mask provided on one surface thereof, and where an upper surface of the Faraday cage is provided with a mesh portion; a first patterning step of forming a first pattern area on the etch substrate; and a second patterning step of forming a second pattern area on the etch substrate after shielding at least a part of the mesh portion with a shutter. The first pattern area includes a first groove pattern having a depth gradient of 0 to 40 nm per 5 mm, and the second pattern area includes a second groove pattern having a depth gradient of 50 to 300 nm per 5 mm.