Copper-Gold Alloy Bus Bar for Plasma Processing
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Solution Overview
Problem
Plasma processing apparatuses face instability due to bus bar oxidation, leading to increased energy loss and reduced performance, as copper bus bars oxidize when exposed to high-frequency currents, and attempts to mitigate this through larger bus bars or coatings result in increased costs or apparatus complexity.
Innovation Solution
A bus bar formed from an alloy of copper and gold, where gold is more concentrated on the surface and copper in the center, with a specific gold-to-copper ratio, reduces oxidation and heat generation by maintaining low resistance while preventing copper oxide formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the bus bar is made large to increase the surface area, then temperature rise of the bus bar can be suppressed, but there is a risk that the enlarged bus bar leads to upsizing of the apparatus and disposition of the bus bar becomes difficult
Solution Approach 1:
The bus bar is designed with non-uniform cross-sectional area along its length, with larger cross-section at the center and smaller cross-section at the ends. This local variation in geometry allows the central region to handle high current density and generate less heat, while the end regions are sized appropriately for connection purposes, thus suppressing temperature rise without requiring the entire bus bar to be oversized
Solution Approach 2:
The cross-sectional area parameter of the bus bar is changed along its length rather than maintaining a uniform cross-section. This parameter variation optimizes the balance between heat dissipation capability and apparatus size, allowing the bus bar to suppress temperature rise in high-current regions while keeping the overall apparatus compact
2Reliability
If the surface of the bus bar is coated with gold and/or silver, then oxidation resistance is improved, but since the bus bar is a large size part, coating the bus bar surface with expensive gold and/or silver results in increase of manufacturing cost
Solution Approach 1:
The bus bar surface is coated with oxidation-resistant material only at the end portions where oxidation would most adversely affect performance, rather than coating the entire surface. This localized coating approach provides sufficient oxidation protection at the critical connection points while significantly reducing the amount of expensive coating material required
Solution Approach 2:
The bus bar employs a composite structure combining a copper core (for electrical conductivity) with an oxidation-resistant coating layer (such as gold or silver) at strategic locations. This composite design achieves both low electrical resistance and oxidation resistance while controlling manufacturing costs by limiting the expensive coating to essential areas
3Reliability
If silver is used as coating material, then oxidation resistance is improved, but silver gradually oxidizes, and thus initial fluctuation of the plasma processing performance may occur
Solution Approach 1:
The bus bar is pre-coated with an oxidation-resistant material before installation and operation. This preliminary protective action prevents oxidation from occurring during initial operation, thereby avoiding fluctuations in plasma processing performance and ensuring stable operation from the start
Solution Approach 2:
The bus bar coating creates an inert or oxidation-resistant environment at the surface, preventing oxygen from reaching and oxidizing the underlying copper or silver. This protective barrier maintains electrical stability and prevents performance fluctuations during plasma processing operations
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 configuration effectively suppresses bus bar oxidation, maintaining plasma processing performance and reducing manufacturing costs by efficiently managing heat and energy loss.
Implementation Method 1
a power supply 41 and a bus bar 42c. The matching circuit 42a is electrically connected to the power supply 41 and the electrode 31a via the bus bar 42c
Implementation Method 2
when a current is passed through the bus bar, a temperature of the bus bar rises due to Joule heat
Implementation Method 3
when the temperature of the bus bar increases, the surface is oxidized and copper oxide is formed
Implementation Method 4
since a high frequency current flows in the vicinity of the bus bar surface due to a skin effect, when copper oxide with a higher resistance than copper is formed on the bus bar surface, the amount of heat generated increases
Data Source
AI summary
According to one embodiment, a plasma processing apparatus includes a chamber being possible to maintain an atmosphere more depressurized than atmospheric pressure, a plasma generator generating a plasma inside the chamber, a gas supplier supplying a gas into the chamber, a placement part positioned below a plasma generation region and placing a processed product thereon, a depressurization part depressurizing the chamber, and a power supply electrically connected to an electrode provided on the placement part via a bus bar. The bus bar is formed of an alloy of copper and gold. Gold is more included than copper on a surface side of the bus bar. The bus bar includes a first layer formed of copper and a second layer covering the first layer and formed of an alloy of copper and gold. Gold is more included than copper on a surface side of the second layer.