Focus Ring Three-Flat Portion Design for Plasma Sheath Uniformity
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Solution Overview
Problem
In plasma processing apparatuses, the consumption of the focus ring leads to changes in the shape and height relationship between the plasma sheath and the processing target object, causing variations in the incident angle of plasma particles, which results in non-uniform hole inclinations and necessitates frequent replacement, reducing throughput.
Innovation Solution
A focus ring with a specific configuration including a first flat portion lower than the mounting surface, a second flat portion lower than the first, and a third flat portion higher than the first, along with inclined surfaces and wall surface portions, maintains the plasma sheath distribution even as it is consumed, reducing the variance in hole inclination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional focus ring with two flat portions is used, then the structure is simple, but the hole inclination becomes non-uniform due to focus ring consumption
Solution Approach 1:
The focus ring is divided into three distinct flat portions (first, second, and third) at different heights, with each portion serving a specific function in maintaining plasma sheath distribution. This segmentation allows the focus ring to compensate for consumption effects and maintain hole inclination uniformity throughout its service life.
Solution Approach 2:
The invention introduces a vertical height dimension variation among the three flat portions, creating a three-dimensional structure where each flat portion is at a different elevation. This dimensional approach enables the focus ring to maintain optimal plasma sheath distribution even as material is consumed during processing.
2Manufacturing precision
If the focus ring is frequently replaced to maintain hole inclination uniformity, then the manufacturing precision is maintained, but the process throughput is reduced
Solution Approach 1:
The focus ring is pre-configured with three flat portions at different heights before installation, anticipating the consumption that will occur during operation. This preliminary structural arrangement ensures that even after significant consumption, the focus ring continues to maintain uniform hole inclination, eliminating the need for frequent replacements and maximizing process throughput.
3Productivity
If the focus ring consumption is allowed to proceed, then the device operates continuously, but the plasma sheath distribution changes causing incident angle variation
Solution Approach 1:
The focus ring structure is designed to dynamically adapt to consumption over time. As material is consumed during continuous operation, the three-flat-portion structure maintains the critical height relationships needed for proper plasma sheath distribution, allowing the system to remain effective throughout the entire service life of the focus ring without requiring intervention.
Data Source
AI summary
A plasma processing apparatus includes a chamber, a mounting table 2 and a focus ring 8. The chamber is configured to process a semiconductor wafer W with plasma. The mounting table 2 is provided within the chamber, and includes a holding surface 9a on which the semiconductor wafer W is mounted. The focus ring 8 is provided to surround the semiconductor wafer W mounted on the holding surface 9a, and includes a first flat portion 8a, a second flat portion 8b and a third flat portion 8c which are formed in sequence from an inner circumferential side of the focus ring 8 toward an outer circumferential side thereof. Here, the first flat portion 8a is lower than the holding surface 9a, the second flat portion 8b is lower than the first flat portion 8a, and the third flat portion 8c is higher than the first flat portion 8a.