RF Coupling Structures for Uniform Plasma Density Control
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Solution Overview
Problem
The formation of a plasma in integrated circuit fabrication chambers using RF sources is a delicate process prone to nonuniformities due to disproportionate RF energy coupling, leading to variations in plasma density and material deposition rates.
Innovation Solution
The use of an apparatus with conductive loops and reactive elements to form a plasma, where the loops exhibit a second value of inductance in the presence of plasma, and the resonant frequency of the coupling structures increases with plasma presence, helping to maintain uniform plasma generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If RF current is coupled into a process station to form ionized plasma material, then plasma formation is enabled to facilitate material deposition, but nonuniform plasma density and disproportionate RF energy coupling occur leading to variations in deposition rates
Solution Approach 1:
The patent divides the single RF coupling approach into multiple separate RF coupling structures (first and second RF coupling structures) that independently couple RF energy to different regions of the plasma volume. This segmentation allows independent control of RF energy distribution, enabling uniform plasma density across the process station by addressing disproportionate coupling in specific regions.
Solution Approach 2:
The patent applies different RF coupling characteristics to different spatial locations within the plasma volume. Each RF coupling structure is positioned and configured to deliver appropriate RF energy to its local region, creating locally optimized plasma conditions that collectively achieve uniform overall plasma density and consistent deposition rates across the substrate.
2Productivity
If RF current coupling is increased to enhance plasma formation, then plasma density increases to improve deposition rate, but nonuniformities and variations in deposition rates increase
Solution Approach 1:
By implementing multiple RF coupling structures that independently control RF energy delivery to different plasma regions, the system can maintain high overall plasma density for improved deposition rates while ensuring each region receives appropriate RF energy. This prevents local nonuniformities that would cause deposition rate variations, thus achieving both high productivity and manufacturing precision.
Solution Approach 2:
The patent employs control systems that monitor plasma conditions and adjust RF energy coupling to each coupling structure dynamically. This feedback mechanism ensures that plasma density is maintained at optimal levels for high deposition rates while preventing nonuniformities, thereby achieving consistent deposition rates across the substrate.
3Reliability
If conventional RF coupling methods are used to form plasma, then plasma generation is achieved, but delicate parameter control is required to ensure repeatable and consistent results
Solution Approach 1:
The patent divides the plasma formation process into multiple independently controlled RF coupling structures, each with its own RF energy delivery system. This segmentation allows independent optimization and control of each coupling structure, reducing the interdependence of parameters and simplifying the overall control system while improving repeatability through localized parameter management.
Solution Approach 2:
The patent utilizes multiple RF coupling structures with adjustable parameters (RF power, frequency, coupling impedance) that can be independently optimized. By changing and controlling these parameters across multiple coupling structures rather than relying on single-parameter control, the system achieves more robust and repeatable plasma formation with reduced sensitivity to individual parameter variations.
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 helps in achieving uniform plasma generation and distribution, reducing variations in material deposition rates and improving the repeatability of semiconductor processing.
Implementation Method 1
one or more conductive loops configured to permit the RF current to conduct from at least a first port of the one or more coupling ports to at least a second port of the one or more coupling ports
Implementation Method 2
one or more conductive loops configured to form a plasma operating in an inductive mode
Implementation Method 3
Each coupling structure of the apparatus may have a resonant frequency configured to increase in response to the presence of the plasma
Data Source
AI summary
An apparatus for forming a plasma may include one or more coupling ports to accept a radiofrequency (RF) current. The apparatus may additionally include one or more coupling structures which may include one or more conductive loops to permit the RF current to conduct from at least a first portion of the one or more coupling ports to at least a second port of the one or more coupling ports. The one or more conductive loops may each be configured to exhibit a first value of inductance in the absence of the plasma and to exhibit a second value of inductance in the presence of the plasma. The one or more coupling structures may each include a reactive element, in which each reactive element is coupled to a corresponding one of the one or more conductive loops so as to form a corresponding number of coupling structures. Each RF coupling structure may have a resonant frequency that increases in response to the presence of the plasma.