RF Power Supply and Matching Network Synchronization for Plasma Etching
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Solution Overview
Problem
Existing semiconductor wafer processing systems using pulsed plasma face challenges with inefficient power coupling due to slow tuning of dynamically adjustable matching networks, leading to sporadic reflected power and reduced plasma power efficiency during etching processes.
Innovation Solution
Implementing an RF power supply with frequency tuning and a matching network that share a common sensor for reading reflected RF power, allowing for synchronized tuning of both the RF power supply and matching network, enabling efficient pulsed plasma processing over a wide process window through specific timing procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a dynamically tuned matching network is used to couple RF power to plasma, then power coupling efficiency is improved, but the tuning speed is too slow compared to the RF pulse length, causing sporadic reflected power and inconsistent matching
Solution Approach 1:
The system performs preliminary tuning of the matching network before the RF pulse is applied. The controller adjusts the matching network parameters in advance based on pre-pulse plasma characteristics measurements, ensuring the network is properly tuned before high power is coupled to the plasma, thereby avoiding reflected power issues during the pulse.
Solution Approach 2:
The system uses feedback from reflected power sensors and plasma characteristic monitors to continuously adjust matching network parameters. The controller receives real-time feedback on plasma impedance changes and automatically retunes the matching network to maintain optimal power coupling efficiency throughout the pulse duration and between pulses.
2Loss of energy
If the matching network is continuously adjusted to maintain plasma match, then power coupling efficiency is improved, but excessive reflected power occurs and plasma power coupling efficiency reduces
Solution Approach 1:
The system implements periodic tuning cycles rather than continuous adjustment. The matching network is tuned at specific intervals (e.g., between pulses or at designated phases), allowing the plasma to stabilize between tuning events. This periodic approach prevents excessive reflected power while maintaining adequate coupling efficiency by syncing tuning actions with the pulsed plasma operation rhythm.
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 approach stabilizes the plasma processing system within less than 6 seconds, minimizing exposure to unstable plasma and improving etch uniformity and selectivity while reducing damage to wafers, thereby enhancing the operational window for pulsed plasma processes.
Implementation Method 1
The power from an RF generator or RF source must be coupled through a dynamically tuned matching network (also referred to as a match unit) to an antenna or electrode within a plasma reactor. The pulsed power is coupled from the antenna or electrode to process gases within the reactor to form a plasma
Implementation Method 2
The matching network matches the, typically, 50 ohms to a complex impedance of the plasma. To facilitate dynamic matching as the plasma characteristics change during processing, the matching network is continuously adjustable to ensure that a match is achieved and maintained throughout processing
Implementation Method 3
The pulsed power is coupled from the antenna or electrode to process gases within the reactor to form a plasma that is used for the etching process
Data Source
AI summary
Embodiments of the present invention generally provide methods and apparatus for pulsed plasma processing over a wide process window. In some embodiments, an apparatus may include an RF power supply having frequency tuning and a matching network coupled to the RF power supply that share a common sensor for reading reflected RF power reflected back to the RF power supply. In some embodiments, an apparatus may include an RF power supply having frequency tuning and a matching network coupled to the RF power supply that share a common sensor for reading reflected RF power reflected back to the RF power supply and a common controller for tuning each of the RF power supply and the matching network.