Faraday Cage Plasma Etching for Multi-Angle Diffraction Gratings
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Solution Overview
Problem
Conventional ion beam etching methods for producing surface relief diffraction gratings on waveguide combiners or coupler lenses require multiple patterning steps and have low etch rates, making them inefficient and complex for manufacturing multiple gratings with different angles and orientations.
Innovation Solution
A method using a Faraday cage in a plasma etching apparatus that allows simultaneous etching of multiple surface relief diffraction gratings with different angles and orientations, utilizing a dielectric substrate with a mask and a Faraday cage positioned above the substrate to control plasma etching through discrete regions with varying angles and orientations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional ion beam etching is used to produce multiple surface relief diffraction gratings with different angles and orientations, then manufacturing precision is achieved, but productivity is significantly reduced due to requiring multiple separate patterning and etch steps
Solution Approach 1:
The patent combines multiple separate patterning and etching steps into a single integrated process. A multi-layer mask structure is used where different mask layers define different grating regions, allowing all gratings with different angles and orientations to be etched simultaneously in one step, thereby maintaining precision while dramatically improving productivity
Solution Approach 2:
The etching process is segmented into multiple independent etching zones within a single chamber, each zone equipped with its own ion beam source and mask. This allows different regions of the substrate to be etched at different angles and orientations simultaneously, resolving the contradiction between precision and productivity
2Manufacturing precision
If conventional ion beam etching systems are used with multiple patterning steps to achieve different grating angles, then manufacturing precision is maintained, but device complexity increases due to multiple vacuum breaks and repatterning operations
Solution Approach 1:
The patent merges multiple patterning operations into a single masking step using a multi-layer mask structure. Different mask layers are deposited and patterned in sequence, but all etching operations are performed in one continuous process without vacuum breaks, thereby maintaining precision while reducing process complexity
Solution Approach 2:
The mask structure is prepared in advance with all necessary pattern layers deposited and defined before the etching process begins. This preliminary preparation allows all subsequent etching steps to proceed simultaneously without requiring intermediate repatterning operations, reducing both complexity and process time
3Manufacturing precision
If ion beam etching is performed at low pressures to minimize ion scattering, then manufacturing precision is improved, but the etching system becomes larger and more complex
Solution Approach 1:
The patent changes the pressure parameter from low pressure to high pressure operation. By operating at elevated pressures, the mean free path of ions is reduced, minimizing scattering effects and maintaining directional control without requiring the complex, large-scale equipment typical of low-pressure ion beam systems
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 high etch rates and eliminates the need for separate patterning steps, allowing efficient production of multiple gratings with different angles and orientations in a single etching step.
Implementation Method 1
plasma etching the substrate to produce a plurality of surface relief diffraction gratings
Data Source
AI summary
A method of etching a substrate to produce a plurality of surface relief diffraction gratings by providing a dielectric substrate having a mask formed on an upper surface thereof, the mask having a plurality of apertures. Further, positioning the substrate on a substrate support in a chamber of a plasma etching apparatus. Even further, positioning a Faraday cage so that an upper portion of the Faraday cage is disposed above the upper surface of the substrate and an electrical connection is maintained between the Faraday cage and the substrate support. The upper portion of the Faraday cage has a plurality of discrete regions having open areas through which the substrate can be plasma etched. Yet further, plasma etching the substrate to produce a plurality of surface relief diffraction gratings. The plurality of surface relief diffraction gratings have at least two subsets having different angles and/or orientations.