Focus Ring Surface Roughness for Stable Plasma Substrate Holding
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Solution Overview
Problem
Conventional plasma treatment devices experience significant temperature differences between the front and back surfaces of the focus ring, leading to substrate displacement and instability during plasma treatment, which can damage the substrate.
Innovation Solution
The focus ring features a placement surface with a lower average cutting level difference and root mean square slope compared to its supported back surface, reducing heat transfer and maintaining substrate stability by using materials like rare earth element oxides and specific surface roughness profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the temperature in the plasma treatment chamber increases due to plasma generation, then the plasma treatment effectiveness is improved, but a large temperature difference occurs between the front and back surfaces of the focus ring causing substrate displacement
Solution Approach 1:
The back surface of the focus ring is designed with non-uniform roughness where the average cutting level difference Rδc in the supported portion is greater than in the non-supported portion. This local variation in surface quality creates differential thermal expansion characteristics that compensate for temperature-induced displacement, maintaining substrate positioning accuracy even at elevated plasma treatment temperatures.
2Reliability
If the average cutting level difference Rδc is increased in the supported portion of the back surface, then thermal expansion compensation is improved and substrate displacement is reduced, but the manufacturing precision requirement increases
Solution Approach 1:
The invention specifies quantitative parameters for surface roughness control: the average cutting level difference Rδc in the supported portion is set to 0.18 μm or more and 0.42 μm or less, while the non-supported portion has Rδc of 0.06 μm or more and 0.15 μm or less. These parameter ranges provide a balanced solution that achieves thermal expansion compensation while remaining manufacturable with conventional precision machining capabilities.
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 design minimizes substrate damage and displacement at the inner peripheral side end portion, ensuring stable substrate holding even at increased plasma treatment chamber temperatures.
Implementation Method 1
When the temperature in a plasma treatment chamber increases due to the conversion of a gas into plasma, a large temperature difference occurs between a front surface and a back surface of an edge ring (focus ring). The average value of a cutting level difference (Rδc) representing a difference between a cutting level at a load-length ratio of 25% in a roughness curve and a cutting level at a load-length ratio of 75% in the roughness curve is greater in a supported portion of the back surface supported by one support member than in the placement surface.
Data Source
AI summary
A focus ring according to the present disclosure includes a placement surface accommodating a substrate to be treated and facing a lower surface of the substrate to be treated, and a back surface located on an opposite side to the placement surface. An average value of a cutting level difference (Rδc) representing a difference between a cutting level at a load-length ratio of 25% in a roughness curve and a cutting level at a load-length ratio of 75% in the roughness curve is greater in a supported portion of the back surface supported by one support member than in the placement surface.