Large Area CVD Diamond Window Uniform Growth via Segmented Microwave Reactor
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Solution Overview
Problem
Current methods for fabricating large polycrystalline diamond windows with high optical quality are hindered by impurity incorporation, non-uniformity, and cracking issues, particularly for diameters greater than 120 mm, due to misalignments and inefficiencies in microwave plasma reactors.
Innovation Solution
A precisely aligned microwave plasma reactor configuration with an annular dielectric window and optimized gas flow, ensuring rotational symmetry and high gas flow rates, coupled with controlled substrate temperature and gas composition, to achieve uniform diamond growth and reduce impurity incorporation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional microwave plasma reactor configurations are used for fabricating large polycrystalline diamond windows, then production capacity is maintained, but impurity incorporation and non-uniformity increase significantly for diameters greater than 120 mm
Solution Approach 1:
The microwave energy coupling is segmented into multiple distributed ports around the reactor chamber, allowing uniform energy distribution across large substrate areas. This segmentation prevents localized hot spots and ensures uniform diamond growth across the entire window surface, resolving the quality uniformity issue for large diameters.
Solution Approach 2:
A precisely engineered annular dielectric window is introduced as an intermediary component between the microwave source and the plasma region. This dielectric window with specific rotational symmetry and precision alignment acts as a mediator to distribute microwave energy uniformly, preventing impurity incorporation and maintaining optical quality across large area windows.
2Manufacturing precision
If reactor misalignments are present in conventional configurations, then device complexity is reduced, but manufacturing precision and optical quality deteriorate for large diameter windows
Solution Approach 1:
The design intentionally incorporates a precisely aligned annular dielectric window with specific rotational symmetry that breaks the conventional symmetric reactor configuration. This controlled asymmetry element serves as a reference for precise alignment, enabling sub-millimeter positioning accuracy and ensuring uniform plasma distribution across large substrates without requiring complex alignment procedures.
Solution Approach 2:
The system employs adjustable reactor parameters including gas flow rates, microwave power distribution, and substrate positioning that can be optimized for different window sizes. These parameter changes allow the same reactor configuration to maintain high optical quality across varying diameter requirements without requiring physical reconfiguration or complex alignment mechanisms.
3Manufacturing precision
If gas flow rates are increased to improve uniformity, then manufacturing precision improves, but energy consumption increases
Solution Approach 1:
The system employs optimized gas flow distribution manifolds with multiple inlet ports and flow control elements that distribute reactant gases uniformly across the large substrate surface. This pneumatic design achieves uniform diamond growth with moderate total gas flow rates by improving flow distribution efficiency, avoiding the need for excessively high overall flow rates that would increase energy consumption.
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 solution enables the production of large (≥125 mm diameter) and thick (≥200 μm) polycrystalline diamond windows with extremely high optical quality across 80% of the area, meeting stringent requirements for applications like high-powered laser beams and radiation-resistant windows.
Implementation Method 1
Source gases including a carbon source and molecular hydrogen are fed into the plasma reactor vessel and can be activated by the standing microwave to form a plasma in high field regions
Implementation Method 2
Chemical vapour deposition (CVD) processes for synthesis of diamond material are now well known in the art
Implementation Method 3
Atomic hydrogen is essential to the process because it selectively etches off non-diamond carbon from the substrate such that diamond growth can occur
Implementation Method 4
The plasma reactor vessel is configured to form a resonance cavity supporting a standing microwave
Implementation Method 5
The plasma reactor vessel is configured to form a resonance cavity supporting a standing microwave
Implementation Method 6
If a suitable substrate is provided in close proximity to the plasma, reactive carbon containing radicals can diffuse from the plasma to the substrate and be deposited thereon
Implementation Method 7
reactive carbon containing radicals can diffuse from the plasma to the substrate and be deposited thereon
Data Source
AI summary
A polycrystalline chemical vapor deposited (CVD) diamond wafer comprising:a largest linear dimension equal to or greater than 125 mm;a thickness equal to or greater than 200 μm; andone or both of the following characteristics measured at room temperature (nominally 298 K) over at least a central area of the polycrystalline CVD diamond wafer, said central area being circular, centered on a central point of the polycrystalline CVD diamond wafer, and having a diameter of at least 70% of the largest linear dimension of the polycrystalline CVD diamond wafer:an absorption coefficient ≤0.2 cm−1 at 10.6 μm; anda dielectric loss coefficient at 145 GHz, of tan δ≤2×10−4.