Focus Ring Elevation Control for Uniform Plasma Etching
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Solution Overview
Problem
In plasma processing apparatuses, the consumption of focus rings affects the uniformity of plasma processing, leading to variations in etching characteristics due to deviations in the height position of the plasma sheath above the focus ring compared to the wafer, especially at the peripheral portions of wafers with varying sizes and thicknesses.
Innovation Solution
A plasma processing apparatus is designed with a mounting table, an acquisition unit, a calculation unit, and an elevation control unit. The apparatus measures the state of the wafer, calculates the required height of the focus ring to maintain a predetermined distance between the wafer and the focus ring, and adjusts the focus ring's position using an elevation mechanism to ensure uniform etching characteristics across the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the focus ring is replaced or its height is adjusted using a drive mechanism, then the height position of the plasma sheath above the focus ring can be maintained, but etching characteristics still vary depending on wafer variations in diameter, thickness, and other parameters
Solution Approach 1:
The focus ring height is made dynamically adjustable through an elevation mechanism that can change the focus ring's height position based on detected wafer state variations. This allows the system to adapt to different wafer parameters (diameter, thickness) by dynamically modifying the focus ring position rather than using a fixed height setting
Solution Approach 2:
The system detects the actual state of the wafer (such as thickness variations) and uses this information to control the elevation mechanism, creating a feedback loop. The detection unit measures wafer parameters, and this measurement feeds back to adjust the focus ring height accordingly, ensuring optimal etching characteristics for each specific wafer
2Device complexity
If the focus ring height is fixed, then the device structure is simple, but etching characteristics deteriorate when wafer parameters vary within standard tolerances
Solution Approach 1:
The system automatically detects wafer state and adjusts the focus ring height without requiring manual intervention or complex external control systems. The elevation mechanism is self-regulating based on the detected wafer parameters, making the system adapt to different wafers autonomously while maintaining relatively simple overall device structure
Data Source
AI summary
A plasma processing apparatus includes a mounting table, an acquisition unit, a calculation unit, and an elevation control unit. The mounting table mounts thereon a target object as a plasma processing target. The elevation mechanism vertically moves a focus ring surrounding the target object. The acquisition unit acquires state information indicating a measured state of the target object. The calculation unit calculates a height of the focus ring at which positional relation between an upper surface of the target object and an upper surface of the focus ring satisfies a predetermined distance based on the state of the target object that is indicated by the state information acquired by the acquisition unit. The elevation control unit controls the elevation mechanism to vertically move the focus ring to the height calculated by the calculation unit.