Confinement Ring Pressure Control in Plasma Chamber
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Solution Overview
Problem
In plasma processing systems with moving electrodes, existing pressure control methods struggle to rapidly stabilize pressure after sudden changes in the chamber volume, leading to prolonged downtime and reduced productivity due to the inefficiencies of closed-loop control algorithms.
Innovation Solution
An open-loop pressure control method is implemented, using empirically derived conductance curves to rapidly adjust the confinement ring positions, followed by closed-loop fine-tuning to achieve and maintain the desired pressure set point, allowing for rapid compensation and stabilization of pressure changes caused by electrode repositioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If closed-loop control algorithms are used to control pressure after electrode repositioning, then pressure stability is maintained, but pressure stabilization time is prolonged
Solution Approach 1:
The system pre-calculates and stores conductance values for different confinement ring positions and chamber gap heights in a lookup table before operation. When electrode repositioning occurs, the controller immediately queries the pre-computed table to determine the optimal confinement ring position, eliminating the need for time-consuming real-time iterative calculations and enabling instantaneous pressure compensation
Solution Approach 2:
The patent replaces the traditional closed-loop feedback control mechanism with an open-loop feedforward control system. Instead of continuously measuring pressure and adjusting confinement ring positions based on error signals, the system uses pre-computed conductance relationships to directly determine the required confinement ring position from the new chamber gap height, significantly reducing stabilization time while maintaining pressure stability
2Adaptability or versatility
If chamber gap is adjusted for different processing conditions, then processing versatility is improved, but pressure control precision deteriorates
Solution Approach 1:
The system pre-computes and stores conductance relationships for multiple chamber gap heights in a lookup table. Each entry in the table contains the optimal confinement ring position corresponding to a specific chamber gap height and desired pressure condition. When processing conditions change and the chamber gap is adjusted, the controller retrieves the pre-calculated parameters from the table, ensuring precise pressure control is maintained across all processing conditions without requiring real-time iterative adjustments
Data Source
AI summary
In a plasma processing chamber, a method and an arrangement to stabilize pressure are provided. The method includes providing coarse pressure adjustments in an open-loop manner and thereafter providing fine pressure adjustments in a closed-loop manner. The coarse pressure adjustments are performed by rapidly re-position confinement rings employing an assumed linear relationship between the conductance and the confinement rings position to bring the pressure in the plasma generating region quickly to roughly a desired set point. The fine pressure adjustments are performed by at least employing mechanical vacuum pump(s), turbo pump(s), confinement ring positioning and/or combinations thereof to achieve a derive pressure set point.