Two-Stage Plasma Substrate Processing for Oxide-Free Graphene Growth
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Solution Overview
Problem
Existing methods for forming graphene films on substrates face challenges due to re-oxidation of the substrate surface during handling, which affects the quality and integrity of the film.
Innovation Solution
A substrate processing method involving a two-stage plasma process is employed, where the substrate is first etched at a raised position to remove natural oxide films using hydrogen-containing plasma at controlled low temperatures, followed by forming the graphene film at a second position on the stage at elevated temperatures, utilizing microwave plasma CVD to maintain high radical density and low electron energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet cleaning using diluted hydrofluoric acid solution is performed to remove natural oxide film, then oxide film removal is improved, but substrate surface re-oxidation occurs during handling and transfer leading to defects
Solution Approach 1:
The patent applies preliminary action by performing oxide film removal through plasma treatment immediately before graphene film formation within the same vacuum chamber. The substrate is loaded with natural oxide film, undergoes plasma cleaning to remove the oxide, and then immediately receives graphene deposition without exposure to atmosphere, eliminating the re-oxidation problem that occurs with conventional wet cleaning and air exposure.
Solution Approach 2:
The patent utilizes an inert vacuum atmosphere throughout the entire process. The vacuum chamber maintains a controlled environment where plasma cleaning and graphene deposition occur sequentially without atmospheric exposure. This inert environment prevents re-oxidation of the substrate surface that would otherwise occur during handling and transfer in air.
2Ease of operation
If substrate is held at fixed position during plasma process, then process control is simplified, but temperature control becomes difficult leading to bubbling phenomenon
Solution Approach 1:
The patent applies dynamics by making the substrate position adjustable rather than fixed. The substrate holder can change its position vertically within the plasma chamber, allowing the substrate to be placed at different heights relative to the plasma generation region. This dynamic positioning enables optimization of both process control and temperature control by adjusting the substrate's distance from the plasma source during different process stages.
3Productivity
If graphene film is formed on substrate with natural oxide film, then film formation process is simplified, but film quality deteriorates due to defects from re-oxidation
Solution Approach 1:
The patent merges the oxide removal process and graphene film formation process into a single integrated vacuum chamber operation. Both processes occur sequentially in the same environment without atmospheric exposure, combining what would traditionally be separate steps (wet cleaning followed by deposition in separate equipment) into one continuous vacuum process, thereby maintaining high film quality while preserving productivity.
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 results in the formation of high-quality, low-defect graphene films by preventing re-oxidation and ensuring excellent contact resistance and adhesion, while reducing the number of processing steps and minimizing substrate damage.
Implementation Method 1
a first plasma process... a second plasma process
Implementation Method 2
controlled etching of oxide films using hydrogen-containing plasma
Implementation Method 3
a first plasma process... a second plasma process
Implementation Method 4
microwave plasma chemical vapor deposition (CVD) apparatus to form a graphene film
Data Source
AI summary
A substrate processing method of processing a substrate having a base film includes a loading process of loading the substrate into a processing container, a first process of performing a first plasma process in a state where the loaded substrate is held at a first position by raising substrate support pins of a stage arranged in the processing container, and a second process of performing a second plasma process while holding the substrate at a second position by lowering the substrate support pins.