RF Pulse Impedance Matching for Stable Plasma Processing
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Solution Overview
Problem
Fluctuations in RF power levels cause instability in plasma conditions, leading to impedance mismatches and increased reflected power, which can extinguish the plasma during processing, making it challenging to maintain stable plasma conditions.
Innovation Solution
A plasma processing system with a controller that calculates a weighted average of load impedances across different power levels to adjust matching elements, ensuring the output impedance of the RF power source matches the load impedance, thereby reducing fluctuations and maintaining stable plasma conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If RF power level is changed during plasma processing, then plasma condition can be adjusted for different processing requirements, but impedance mismatch occurs causing plasma instability and potential extinction
Solution Approach 1:
The patent implements dynamic impedance matching by continuously adjusting the matching network parameters in real-time as RF power levels change. The control unit monitors plasma impedance and automatically tunes the matching network to maintain optimal power transfer, allowing plasma conditions to be adjusted across different power levels without causing plasma extinction. This dynamic adaptation resolves the contradiction between plasma condition adaptability and plasma stability.
2Productivity
If RF power is periodically changed to multiple power levels, then etching process can be optimized, but reflected power increases due to impedance mismatch
Solution Approach 1:
The patent employs a feedback control mechanism where the control unit continuously monitors the plasma impedance and reflected power levels. When RF power is periodically changed to multiple power levels for etching optimization, the system detects impedance changes and automatically adjusts the matching network parameters to minimize reflected power. This closed-loop feedback ensures that productivity benefits from multi-power-level processing while energy loss from reflection is minimized.
3Reliability
If matching element is adjusted for each power level, then impedance matching can be maintained, but system complexity increases
Solution Approach 1:
The patent implements a self-adjusting impedance matching system where the control unit automatically monitors plasma impedance and tunes the matching network parameters without requiring manual intervention. The system uses real-time measurements of reflected power and plasma impedance to autonomously optimize the matching conditions across different RF power levels. This self-service approach maintains reliable impedance matching while minimizing the need for complex external control systems.
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
The system achieves stable plasma maintenance by minimizing reflected power fluctuations, ensuring consistent plasma conditions and preventing plasma extinction during processing.
Implementation Method 1
The RF power source is electrically connected to the matcher and generates a periodic RF pulse that includes a first power level, a second power level, and a third power level
Implementation Method 2
the plasma condition affects the accuracy of the substrate processing... during an etching process using plasma, the condition of the plasma affects the shape of the etching pattern
Implementation Method 3
The controller controls a matching element included in the matcher based on the load impedance calculated in each of the first time interval, the second time interval, and the third time interval
Data Source
AI summary
A plasma processing system includes a plasma processing chamber, a substrate support, a matching box, an RF power source, and a controller. The substrate support is disposed in the plasma processing chamber. The matching box is electrically connected to the substrate support. The RF power source is electrically connected to the matching box to generate a periodic RF pulse that includes a first power level, a second power level, and a third power level. The controller calculates the load impedance based on the reflected power of the RF pulse in each of first, second, and third time intervals during which the first, second, and third power levels are supplied, respectively, and controls a matching element included in the matching box based on the load impedance calculated in each of the first, second, and third time intervals.