Dynamic Control Band for RF Plasma Current Ratio
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Solution Overview
Problem
Existing plasma processing reactor designs focus on minimizing reflected power by controlling the RF power delivery, but this approach has fixed current ratio limits for each operating mode, limiting effective tuning and leading to processing non-uniformities such as M-shape etch profiles.
Innovation Solution
The method involves actively controlling the current ratio between RF coils by setting dynamic control limits based on the current ratio set point and operating mode, measuring actual currents, and adjusting the divider capacitor to maintain the current ratio within these limits, allowing real-time tuning of the impedance pathway.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed current ratio limits are used for each operating mode, then the control system is simple, but the tuning effectiveness is limited and processing non-uniformities occur
Solution Approach 1:
The patent applies dynamics by transitioning from fixed current ratio limits to dynamic control limits that adapt in real-time. The control limits are continuously adjusted based on the actual operating mode and measured plasma parameters, allowing the system to respond to changing conditions and maintain optimal performance across different operating scenarios.
Solution Approach 2:
The patent implements parameter changes by modifying the current ratio limits based on operating conditions. The control system dynamically adjusts the current ratio setpoints and limits according to the detected operating mode and plasma state, enabling the system to optimize processing uniformity across varying operational parameters.
2Loss of energy
If reflected power control is used, then the RF power delivery is controlled, but the current ratio tuning is limited
Solution Approach 1:
The patent applies feedback by implementing a closed-loop control system that continuously monitors the actual current ratio and compares it to the dynamic control limits. The system uses this feedback information to adjust the RF power distribution and maintain the current ratio within optimal boundaries, thereby improving both energy efficiency and tuning capability.
Solution Approach 2:
The patent introduces an intermediary control mechanism that mediates between the reflected power control and current ratio tuning. The dynamic control limits act as an intermediary parameter that translates reflected power considerations into specific current ratio setpoints, enabling coordinated optimization of both energy efficiency and plasma uniformity.
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 optimizes current ratio control, reducing processing non-uniformities and improving plasma etch processes by dynamically adjusting the current ratio set points, enhancing the efficiency of RF power coupling and plasma formation.
Implementation Method 1
Inductively coupled plasma (ICP) process reactors generally form plasmas by inducing current in a process gas disposed within the process chamber via one or more inductive coils disposed outside of the process chamber. When radio frequency (RF) current is fed to the inductive coils via an RF feed structure from an RF power supply, an inductively coupled plasma can be formed inside the chamber from an electric field generated by the inductive coils.
Data Source
AI summary
Methods and apparatus for plasma processing are provided herein. The method for controlling current ratio in a substrate processing chamber may include (a) providing a first RF signal to a first RF coil and a second RF coil at a first current ratio set point and a first current operating mode, (b) determining a first dynamic control limit for the first current ratio set point based on a value of the first current ratio set point and the first current operating mode, (c) measuring an amount of current supplied to each of the first and second coils, (d) determining the actual current ratio based on the measured amounts of current supplied to each of the first and second coils, (e) determining whether the actual current ratio determined is within the dynamic control limits, and (f) repeating steps (b)-(e) until the actual current ratio determined is within the dynamic control limits.