Three-Piece Focus Ring with Movable Middle Segment
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Solution Overview
Problem
The existing plasma etching apparatuses face challenges in controlling the etching characteristics, particularly in the edge portion of semiconductor wafers, due to wear of the focus ring, leading to uneven etching rates and shape tilting, as the height of the focus ring changes, making it difficult to maintain uniformity across the wafer.
Innovation Solution
A three-piece focus ring configuration is introduced, with an inner, middle, and outer focus ring, where the middle focus ring is movable in the vertical direction using a piezo actuator, allowing precise adjustment to match the wear and maintain uniform sheath heights, thus controlling the etching rate and preventing shape tilting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a two-piece focus ring (fixed inner focus ring and movable outer focus ring) is used to control the etching rate in the edge portion of the wafer, then the etching rate in the edge portion can be adjusted, but the etching rate in the entire wafer is shifted, making it difficult to control the etching characteristic only in the edge portion
Solution Approach 1:
The focus ring is divided into three separate rings: a fixed inner focus ring, a movable middle focus ring, and a fixed outer focus ring. This segmentation allows independent control of different regions of the wafer, enabling adjustment of the etching rate in the edge portion without affecting the entire wafer surface uniformly.
Solution Approach 2:
The movable middle focus ring is positioned to correspond specifically with the edge portion of the wafer, allowing localized control of plasma density and etching rate in that region. The fixed inner and outer focus rings maintain their positions to preserve overall etching characteristics across the wafer surface.
2Reliability
If the focus ring is made movable to compensate for wear and maintain etching uniformity, then the etching characteristic can be controlled, but the structure becomes more complex and the reliability decreases due to additional moving parts
Solution Approach 1:
By dividing the focus ring into three separate rings, only the middle ring requires a moving mechanism for wear compensation, while the inner and outer rings remain fixed. This reduces the complexity compared to making the entire focus ring movable, while still achieving reliable etching uniformity through localized adjustment.
Solution Approach 2:
The movable middle focus ring can be automatically adjusted using a piezoelectric actuator to compensate for wear, maintaining the optimal height position without manual intervention. This self-adjusting capability ensures consistent etching uniformity over time while minimizing the need for complex manual calibration mechanisms.
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 maintains uniform etching rates across the wafer, prevents sharp increases in etching rates at the edge, and extends the life of the focus ring by compensating for wear, ensuring consistent processing characteristics.
Implementation Method 1
a piezo actuator, which is a non-contact drive unit, is connected to the middle focus ring
Implementation Method 2
The focus ring has a function to control plasma near the circumference of the wafer and to improve the in-plane uniformity in the etching rate of the wafer
Data Source
AI summary
A substrate processing apparatus includes a process chamber, a stage that is disposed in the process chamber and on which a substrate is placeable, a moving mechanism, and a focus ring. The focus ring is disposed on the stage and includes an inner focus ring disposed close to the substrate placed on the stage, a middle focus ring that is disposed outside of the inner focus ring and is movable in a vertical direction by the moving mechanism, and an outer focus ring that is disposed outside of the middle focus ring.