Diamond Membrane Fabrication via Selective Etching
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Solution Overview
Problem
Conventional methods for fabricating thin diamond membranes result in non-uniform thickness, high surface roughness, and residual strain, leading to vulnerability and degradation of wave guiding properties and optical centers.
Innovation Solution
A method involving a substrate with a sub-surface layer of different crystallographic structure, a support structure made of diamond material, and selective etching to create a thin diamond membrane connected to a thicker support structure, which facilitates handling and reuse of substrates, reducing costs and improving membrane quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional chemical vapour deposition with mechanical polishing and chemical etching is used, then thin diamond membranes can be fabricated, but the membranes have non-uniform thickness and high surface roughness
Solution Approach 1:
A sub-surface layer with different crystallographic structure is created in advance within the diamond substrate before membrane fabrication. This pre-prepared layer serves as a selective etching target that enables precise thickness control and smooth surfaces during the subsequent membrane release process, eliminating the need for mechanical polishing.
Solution Approach 2:
The crystallographic structure parameter of the diamond substrate is changed by creating a sub-surface layer with different crystal orientation or phase. This parameter change makes specific regions selectively etchable, enabling precise control over membrane thickness and surface quality without compromising manufacturing complexity.
2Reliability
If ion implantation and lift off techniques are used, then free-standing thin diamond membranes can be fabricated, but residual built-in strain and damage are introduced making membranes vulnerable to breakage and bowing
Solution Approach 1:
The harmful sub-surface layer with compromised structural integrity is selectively removed through etching. This extraction eliminates the source of residual strain and damage that would otherwise remain in the membrane, preventing breakage and bowing while maintaining a simple fabrication process.
Solution Approach 2:
The sub-surface layer, which initially represents a harmful defect or weakened region, is converted into a beneficial tool for selective etching. By making this layer etchable through crystallographic modification, it serves as a sacrificial release agent that enables clean membrane separation without introducing residual damage.
3Ease of operation
If thin diamond membranes are fabricated without support structure, then membrane quality is improved, but handling and processing become difficult due to vulnerability to breakage and bowing
Solution Approach 1:
The diamond structure is segmented into two distinct regions: a thin membrane region for optical quality and a thicker support structure region for mechanical strength. The sub-surface layer enables selective etching to create this segmentation, allowing the thin membrane to be supported by a robust structure without compromising either handling ease or optical properties.
4Productivity
If substrates are discarded after membrane fabrication, then membrane quality is maintained, but production costs increase due to material waste
Solution Approach 1:
Instead of discarding the entire substrate, only the sacrificial sub-surface layer is selectively removed through etching. The remaining substrate structure is recovered and can be reused for fabricating additional membranes, significantly reducing material waste and production costs while maintaining membrane quality through the consistent sub-surface layer release mechanism.
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
The method produces high-quality, thin diamond membranes with reduced bowing and breakage, suitable for optical applications, and enables large-scale production at lower costs by reusing substrate materials.
Implementation Method 1
selectively removing the second region of the diamond material from the substrate by etching away at least a portion of the sub-surface layer of the substrate
Implementation Method 2
Coupling of the formed support structure to the first surface of the substrate may be effected by virtue of surface tension and/or Van der Walls forces
Implementation Method 3
Coupling of the formed support structure to the first surface of the substrate may be effected by virtue of surface tension and/or Van der Walls forces
Data Source
AI summary
The present disclosure provides a method of fabricating a diamond membrane. The method comprises providing a substrate and a support structure. The substrate comprises a diamond material having a first surface and the substrate further comprises a sub-surface layer that is positioned below the first surface and has a crystallographic structure that is different to that of the diamond material. The sub-surface layer is positioned to divide the diamond material into first and second regions wherein the first region is positioned between the first surface and the sub-surface layer. The support structure also comprises a diamond material and is connected to, and covers a portion of, the first surface of the substrate. The method further comprises selectively removing the second region of the diamond material from the substrate by etching away at least a portion of the sub-surface layer of the substrate.