Plasma Reactor Ground Ring Layout for Uniform RF Etching
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Solution Overview
Problem
Conventional capacitively coupled plasma reactors face challenges in achieving uniform plasma density distribution due to the cyclical accumulation of harmonic RF power, leading to non-uniform etching rates and high plasma density at the wafer center, which existing methods cannot effectively address.
Innovation Solution
The plasma reactor design incorporates a low dielectric constant insulating ring and a harmonic filter in the RF match network to dissipate harmonic RF power, preventing its cyclical accumulation and ensuring uniform plasma distribution by adjusting impedance proportions and using ceramic materials to manage thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional insulating ring with high dielectric constant is used, then electrical insulation is adequate, but harmonic RF power accumulates cyclically causing non-uniform plasma distribution
Solution Approach 1:
The patent changes the dielectric constant parameter of the insulating ring from conventional high values to less than 3.5. This parameter change allows the insulating ring to dissipate harmonic RF power effectively while maintaining electrical insulation, thereby preventing cyclical accumulation of harmonic power and achieving uniform plasma distribution across the wafer surface.
Solution Approach 2:
The patent converts the previously harmful harmonic RF power accumulation into a beneficial dissipation mechanism. By selecting insulating ring material with dielectric constant less than 3.5, the harmonic RF power that would normally accumulate and cause non-uniformity is instead dissipated through the insulating ring, transforming a harmful effect into a useful plasma uniformity enhancement.
2Manufacturing precision
If a low dielectric constant insulating ring is used to improve plasma uniformity, then plasma distribution improves, but the insulating ring expands due to thermal effects causing long-term instability
Solution Approach 1:
The patent employs composite material structure by combining the low dielectric constant insulating ring (made of polymer material) with a ceramic ring having low thermal expansion coefficient. This composite structure allows the polymer ring to provide harmonic RF power dissipation while the ceramic ring compensates for thermal expansion, maintaining dimensional stability and ensuring long-term plasma processing stability.
Solution Approach 2:
The ceramic ring acts as an intermediary element between the polymer insulating ring and the metal components. It provides thermal stability and mechanical support while allowing the polymer ring to function optimally for harmonic RF power dissipation, mediating between the thermal effects and the electrical insulation function.
3Use of energy by moving object
If harmonic RF power is allowed to flow freely, then RF power transmission is efficient, but plasma etching uniformity deteriorates due to cyclical accumulation
Solution Approach 1:
The patent extracts the harmful harmonic RF power from the main RF power transmission path by providing a dedicated dissipation path through the insulating ring. This allows the fundamental RF power to be transmitted efficiently for plasma generation while the harmonic power is separately dissipated through the insulating ring, preventing its cyclical accumulation and its harmful effect on etching 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 solution significantly improves plasma etching uniformity, reducing etching rate discrepancies from 10% to less than 1% and maintaining long-term stability by minimizing harmonic RF power's impact on plasma density, thereby enhancing processing efficiency and reducing development costs.
Implementation Method 1
an insulating ring with a dielectric constant being less than 3.5 provided between the base and the first conductive ground ring
Implementation Method 2
the couple ring is made of a first ceramic material which has a thermal conductivity higher than that of the insulating ring
Data Source
AI summary
A plasma reactor includes: a process chamber, at the inner bottom of the process chamber being provided a base, the base being connected to a RF power source via a RF match network, wherein a to-be-processed wafer is held above the base, an upper electrode assembly is provided at the inner top of the process chamber, and a plasma processing space is arranged between the base and the upper electrode assembly; a first conductive ground ring surrounding the outer periphery of the base; a second conductive ground ring connected between the outer sidewall of the first conductive ground ring and the inner sidewall of the process chamber, a plurality of gas channels being provided on the second conductive ground ring such that gas in the plasma processing space can be exhausted through the plurality of gas channels; an insulating ring provided between the base and the first conductive ground ring, wherein dielectric constant of the insulating ring is less than 3.5.