Plasma Ion Energy Distribution Control via RF Phase
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Solution Overview
Problem
Control of ion energy distribution in plasma processes is challenging due to high frequency RF signals causing non-uniformities and incompatibility with process chamber components, particularly electrostatic chucks.
Innovation Solution
The method involves supplying RF signals with specific frequencies and periods to an electrode beneath a substrate support, where the phase between these signals is controlled to manage the ion energy distribution in a process chamber, using a combination of fundamental and harmonic frequencies to maintain constant total ion flux while optimizing energy distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high frequency RF signals are used to control ion energy distribution, then the width of IED can be decreased, but process non-uniformities occur due to wavelength being comparable to critical dimensions
Solution Approach 1:
The patent applies periodic pulsed RF signals with specific duty cycles and frequencies to control ion energy distribution. By using pulsed signals rather than continuous high frequency signals, the method achieves IED control while avoiding the non-uniformity problems associated with high frequency continuous waves. The pulsed nature allows ions to be accelerated in controlled bursts, maintaining energy distribution control without wavelength-related uniformity issues.
Solution Approach 2:
The patent changes multiple RF signal parameters including frequency, amplitude, and duty cycle to achieve desired ion energy distribution. Instead of relying solely on high frequency signals, the method adjusts the combination of frequencies and their temporal characteristics (duty cycle) to control IED width and shape, thereby avoiding the harmful effects of high frequency while maintaining precision control.
2Manufacturing precision
If high frequency RF signals are used to control ion energy distribution, then IED width can be reduced, but compatibility with process chamber components such as electrostatic chuck is compromised
Solution Approach 1:
By using pulsed RF signals with adjustable duty cycles, the patent enables operation at frequencies that are compatible with existing chamber components while still achieving precise IED control. The periodic on-off nature of the pulses allows the electrostatic chuck and other components to respond appropriately without the incompatibility issues that arise with continuous high frequency signals.
Solution Approach 2:
The patent employs dynamically adjustable RF signal parameters including frequency, amplitude, and duty cycle that can be optimized for different process conditions and component configurations. This dynamic control allows the system to adapt to various chamber components like electrostatic chucks while maintaining precise ion energy distribution control, thereby improving versatility and compatibility.
3Device complexity
If single frequency RF signal is used, then system complexity is low, but ion energy distribution control precision is insufficient
Solution Approach 1:
The patent segments the RF signal into multiple frequency components with different duty cycles and phases. By using multiple RF signals at different frequencies (e.g., fundamental and harmonic frequencies) rather than a single frequency, the system achieves superior IED control precision. Each frequency component contributes differently to the overall ion acceleration, enabling fine-tuned control of the energy distribution shape and width.
Solution Approach 2:
The patent creates a composite RF signal structure by combining multiple frequency components (fundamental and harmonic frequencies) with specific amplitude and phase relationships. This composite signal approach enables precise control of ion energy distribution that cannot be achieved with single frequency signals, while the complexity is managed through coordinated control of the multiple signal parameters.
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 allows for selective control of ion energy distribution, enhancing etching processes by achieving desired ion flux at specific energies without increasing total ion flux, thus preventing non-uniformities and component incompatibility issues.
Implementation Method 1
supplying a first RF signal having a first frequency and a first period from an RF power source to a first electrode
Implementation Method 2
controlling a phase between the first and second periods of the first and second RF signals to control an ion energy distribution of a plasma formed in the process chamber
Implementation Method 3
controlling the phase between the first and second periods of the first and second RF signals to control an ion energy distribution of a plasma
Data Source
AI summary
Methods and apparatus for controlling a plasma are provided herein. In some embodiments, a method may include supplying a first RF signal having a first frequency and a first period from an RF power source to a first electrode, wherein the first period is a first integer number of first cycles at the first frequency; supplying a second RF signal having a second frequency and a second period from the RF power source to the first electrode, wherein the second period is a second integer number of second cycles at the second frequency and wherein a first multiplicative product of the first frequency and the first integer number is equal to a second multiplicative product of the second frequency and the second integer number; and controlling the phase between the first and second periods to control an ion energy distribution of the plasma formed in a process chamber.