Broadband Filter Assembly for Plasma Chamber RF Leakage
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Solution Overview
Problem
Current plasma processing chambers face challenges in controlling critical dimension uniformity and preventing undesirably large RF currents from flowing to ground, leading to reduced RF power transfer efficiency, safety issues, and hardware damage, especially when dealing with broad frequency RF power.
Innovation Solution
A broadband frequency filter assembly is introduced, comprising impedance producing elements connected in series with grounded impedance elements, forming common mode chokes by winding conductive leads around a toroid core, to minimize RF leakage currents and prevent them from reaching grounded components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional filtering techniques are used to block RF frequencies, then narrow range frequencies are filtered, but broad frequency spectrum RF currents cannot be effectively blocked
Solution Approach 1:
The filter assembly is divided into multiple impedance producing elements (first, second, third, and fourth elements) connected in series, each contributing to the overall impedance. This segmentation allows the filter to handle broad frequency spectra by distributing the filtering function across multiple components rather than relying on a single narrow-band filter.
Solution Approach 2:
The patent employs common mode chokes with specific inductance values and capacitor values that are selected to provide effective impedance across a broad frequency range. By carefully choosing these electrical parameters (inductance, capacitance, resistance), the filter assembly achieves effective RF current blocking for shaped DC pulses and other broad spectrum RF signals.
2Power
If RF power is increased to achieve higher ion energy for etching, then etching capability improves, but RF leakage currents increase causing hardware damage and safety issues
Solution Approach 1:
The filter assembly acts as an intermediary component placed between the RF power source and the plasma processing chamber. It provides a controlled path for RF currents, allowing desired RF power to reach the plasma while blocking harmful leakage currents from reaching grounded hardware components, thus protecting the system while maintaining high ion energy capability.
Solution Approach 2:
The filter assembly converts the harmful RF leakage currents into a beneficial filtering action. By using impedance producing elements that create high impedance to RF frequencies, the filter transforms what would be damaging leakage currents into a controlled signal path, effectively protecting hardware while allowing the RF power needed for high ion energy etching.
3Manufacturing precision
If multi-zone heating assembly is added to control critical dimension uniformity, then heating control improves, but device complexity increases
Solution Approach 1:
The heating assembly is divided into multiple independently controllable heating zones, each with its own power control. This segmentation allows precise temperature control across different regions of the substrate, enabling critical dimension uniformity to be maintained while using a modular structure that can be controlled through software rather than requiring complex mechanical adjustments.
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 filter assembly effectively reduces RF leakage currents across a wide range of frequencies, enhancing RF power transfer efficiency, ensuring personnel safety, and reducing hardware damage, while maintaining high ion energy for etching high aspect ratio features.
Implementation Method 1
The impedance producing elements each comprise a common mode choke that is formed by winding the first and second conductive leads around a toroid shaped core
Data Source
AI summary
Embodiments described herein are applicable for use in all types of plasma assisted or plasma enhanced processing chambers and also for methods of plasma assisted or plasma enhanced processing of a substrate. More specifically, embodiments of this disclosure include a broadband filter assembly, also referred to herein as a filter assembly, that is configured to reduce and/or prevent RF leakage currents from being transferred from one or more RF driven components to a ground through other electrical components that are directly or indirectly electrically coupled to the RF driven components and ground with high input impedance (low current loss) making it compatible with shaped DC pulse bias applications.