Dual-RF Plasma Phase Control for Uniform Etching
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Solution Overview
Problem
Existing plasma processing methods face challenges in achieving uniformity of etching rates across substrates due to resonance between the plasma processing chamber and the sheath, leading to inefficiencies and non-uniform plasma formation.
Innovation Solution
The method controls the supply of a first RF frequency based on the phase of a second RF frequency lower than the first, using a controller to store predetermined phase ranges calculated from the reactance and sheath thickness, thereby suppressing plasma formation at resonant phases to maintain uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a first RF with a first frequency is supplied to form plasma, then plasma formation efficiency is improved, but resonance between the chamber and sheath causes non-uniform plasma distribution
Solution Approach 1:
The patent applies periodic action by controlling the supply of first RF in a periodic manner synchronized with the phase of the second RF. The first RF is supplied only during specific phase ranges (e.g., 0 to 90 degrees or 270 to 360 degrees) of the second RF cycle, creating a pulsed plasma formation pattern that avoids resonant conditions while maintaining efficient plasma generation during favorable phases.
Solution Approach 2:
The patent implements preliminary action by first supplying the second RF to establish a stable electric field and determine the resonant phase conditions before controlling the first RF supply. The phase information from the second RF is used in advance to gate the first RF supply, ensuring that plasma formation occurs only when chamber-sheath resonance will not degrade uniformity.
2Productivity
If the first RF is continuously supplied for plasma processing, then processing speed is improved, but harmonics and resonance lead to non-uniform etching rates
Solution Approach 1:
The patent resolves this contradiction by implementing periodic gating of the first RF supply based on the phase of the second RF. Instead of continuous supply, the first RF is periodically enabled only during specific phase windows where chamber-sheath resonance effects are minimized. This maintains high processing speed during favorable phases while eliminating uniformity degradation from resonant harmonics.
Solution Approach 2:
The system uses feedback from the phase detection of the second RF to control the first RF supply timing. The controller monitors the phase information from the second RF and uses this feedback to gate the first RF supply, creating a closed-loop control system that dynamically adjusts plasma formation timing to avoid resonant conditions while maintaining processing efficiency.
3Reliability
If a second RF with a second frequency is supplied to control the electric field, then electric field control is improved, but coordination with the first RF requires complex phase management
Solution Approach 1:
The patent uses feedback from the phase detection of the second RF to control the timing of the first RF supply. The controller measures the phase information from the second RF and uses this feedback signal to gate the first RF, creating a synchronized dual-RF system. This feedback mechanism simplifies the coordination complexity by providing real-time phase information that directly controls the first RF gating, eliminating the need for complex independent timing management.
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 enhances in-plane uniformity of the etching rate by controlling plasma formation, suppressing harmonics, and ensuring consistent processing across substrates.
Implementation Method 1
forming a plasma of the processing gas between the upper electrode and the lower electrode by supplying a first RF having a first frequency to the upper electrode or the lower electrode
Implementation Method 2
controlling an electric field formed between the upper electrode or the lower electrode and the plasma by supplying a second RF having a second frequency lower than the first frequency
Data Source
AI summary
The present disclosure provides a substrate processing technology with good in-plane uniformity. A plasma processing method according to the present disclosure includes: disposing a substrate on a substrate support, supplying a processing gas, into the chamber, for processing the substrate, forming a plasma of the processing gas between the upper electrode and the lower electrode by supplying a first RF having a first frequency to an upper electrode or a lower electrode, and controlling an electric field formed between the upper electrode or the lower electrode and the plasma by supplying a second RF having a second frequency lower than the first frequency to the upper electrode or the lower electrode, in which the step of forming the plasma includes controlling the supply of the first RF based on a phase of the second RF.