CVD Diamond Doping via High-Velocity Gas Injection
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Solution Overview
Problem
Current methods for growing synthetic diamond materials using chemical vapor deposition (CVD) face challenges in achieving uniform dopant concentration and high doping levels, particularly for boron-doped diamond films, which are essential for electronic and sensor applications, due to limitations in gas flow rate and geometry.
Innovation Solution
A method involving a microwave plasma reactor with an axially oriented gas flow configuration and high velocity gas flow, utilizing multiple inlet nozzles to inject process gases directly towards the substrate, allowing for uniform doping and high boron incorporation in both polycrystalline and single crystal diamond materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional gas flow methods are used in CVD diamond growth, then the process is simpler to implement, but uniform dopant concentration cannot be achieved and doping levels remain low
Solution Approach 1:
The gas flow system is segmented into multiple independent inlet nozzles (at least three nozzles) positioned at different locations and angles relative to the substrate. Each nozzle delivers process gas independently, allowing precise control of gas distribution patterns across the substrate surface, which enables uniform dopant incorporation throughout the diamond film thickness and area.
Solution Approach 2:
Different regions of the substrate receive optimized gas flow conditions through the multiple nozzles. The nozzles are positioned and angled to create localized high-velocity gas jets that impinge on specific areas, ensuring uniform dopant delivery across the entire substrate surface. This local optimization of gas flow parameters achieves consistent doping throughout the film while maintaining overall system simplicity.
2Quantity of substance
If high dopant concentrations are achieved in CVD diamond, then metallic conduction is obtained, but growth rate decreases and material quality deteriorates
Solution Approach 1:
The process gas is pre-mixed with dopant (boron) at optimized concentrations before entering the reaction chamber. Multiple nozzles deliver this pre-prepared gas mixture in high-velocity streams that impinge on the substrate, ensuring uniform and sufficient dopant supply throughout the growth process. This preliminary preparation of gas composition enables high boron incorporation (achieving metallic conduction at >10^20 atoms/cm³) without disrupting the diamond growth kinetics.
3Productivity
If microwave plasma is used for CVD diamond growth, then power efficiency and growth rate are improved, but controlling dopant incorporation becomes more challenging
Solution Approach 1:
The multiple nozzle configuration provides inherent feedback control for dopant incorporation. By positioning nozzles at specific angles and locations, the system self-regulates gas distribution patterns that maintain uniform dopant delivery across the substrate. The high-velocity gas streams from multiple nozzles create consistent plasma conditions and reactant supply, enabling precise control of boron incorporation levels while maintaining high growth rates under microwave plasma conditions.
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 approach enables the growth of synthetic diamond materials with uniform dopant distribution over large areas and high boron concentrations, achieving metallic conduction while maintaining good growth rates and material quality, surpassing previous limitations in dopant incorporation.
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
a microwave generator for forming the plasma; a coupling configuration for feeding microwaves from the microwave generator into the plasma chamber
Implementation Method 3
CVD processes for manufacture of synthetic diamond material are now well known in the art
Implementation Method 4
reactive carbon containing radicals can diffuse from the plasma to the substrate and be deposited thereon
Implementation Method 5
Atomic hydrogen is believed to be essential to the process because it selectively etches off non-diamond carbon from the substrate such that diamond growth can occur
Implementation Method 6
systems in which process gas is injected into the plasma chamber at high velocity to establish convective transfer of activated gas species from the plasma to the substrate
Data Source
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AI summary
A method of manufacturing synthetic CVD diamond material, the method comprising: providing a microwave plasma reactor comprising: a plasma chamber; one or more substrates disposed in the plasma chamber providing a growth surface area over which the synthetic CVD diamond material is to be deposited in use; a microwave coupling configuration for feeding microwaves from a microwave generator into the plasma chamber; and a gas flow system for feeding process gases into the plasma chamber and removing them therefrom, injecting process gases into the plasma chamber; feeding microwaves from the microwave generator into the plasma chamber through the microwave coupling configuration to form a plasma above the growth surface area; and growing synthetic CVD diamond material over the growth surface area, wherein the process gases comprise at least one dopant in gaseous form, selected from a one or more of boron, silicon, sulphur, phosphorous, lithium and beryllium at a concentration equal to or greater than 0.01 ppm and/or nitrogen at a concentration equal to or greater than 0.3 ppm, wherein the gas flow system includes a gas inlet comprising one or more gas inlet nozzles disposed opposite the growth surface area and configured to inject process gases towards the growth surface area, and wherein the process gases are injected towards the growth surface area at a total gas flow rate equal to or greater than 500 standard cm3 per minute and/or wherein the process gases are injected into the plasma chamber through the or each gas inlet nozzle with a Reynolds number a Reynolds number in a range 1 to 100.