Plasma Etching Duty-Cycle Control for Lower Chamber Wall Ion Energy
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Solution Overview
Problem
In plasma processing apparatuses, high potential differences between the chamber main body and plasma lead to increased ion energy, causing particle contamination of the substrate and reduced etching rates, necessitating a method to suppress this effect.
Innovation Solution
A plasma processing method involving a duty ratio of DC voltage application to the lower electrode of less than 40%, specifically using multiple DC power supplies and a controller to control the application and supply of radio frequency power, reducing ion energy to the chamber walls while maintaining etching efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the potential difference between the chamber main body and plasma is increased to increase ion energy for etching, then the etching rate is improved, but the energy of ions irradiated to the inner wall of the chamber main body is increased causing particle contamination
Solution Approach 1:
The patent applies periodic DC voltage to the lower electrode with a duty ratio of 40% or less, creating pulsed ion bombardment cycles. During the off-period, ion energy to the chamber wall is reduced, preventing particle generation while maintaining etching capability during the on-period. This temporal modulation resolves the contradiction between achieving high etching rates and preventing wall contamination.
Solution Approach 2:
The patent changes the voltage application parameter from continuous to periodic with controlled duty ratio, and adjusts the plasma potential parameter to optimize the balance between ion energy for etching and ion energy to chamber walls. By dynamically controlling these parameters, the system achieves high etching rates while suppressing particle contamination.
2Productivity
If DC voltage is continuously applied to the lower electrode to maintain high etching rate, then substrate etching efficiency is improved, but ion energy to chamber walls remains high causing contamination
Solution Approach 1:
The patent implements periodic DC voltage application with duty ratio control (40% or less), creating alternating periods of high and low ion energy. During voltage application periods, etching proceeds efficiently; during off-periods, ion energy to chamber walls drops, preventing particle release. This periodic modulation simultaneously achieves high etching efficiency and suppresses contamination.
Solution Approach 2:
The patent maintains continuous plasma generation through RF power while modulating DC voltage periodically. This ensures continuous useful action for etching while the periodic DC component controls ion direction and energy distribution, preventing wall contamination without interrupting the overall etching process.
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 method effectively suppresses substrate etching rate decreases and reduces ion energy to the chamber walls, minimizing particle contamination and maintaining etching performance.
Implementation Method 1
The radio frequency power supply is configured to supply a radio frequency power for exciting a gas supplied into the chamber
Implementation Method 2
applying the negative DC voltage to the lower electrode from the one or more DC power supplies to attract ions in the plasma onto the substrate
Implementation Method 3
reducing ion energy to the chamber walls while maintaining etching efficiency
Data Source
AI summary
A decrease of an etching rate of a substrate can be suppressed, and energy of ions irradiated to an inner wall of a chamber main body can be reduced. A plasma processing apparatus includes a DC power supply configured to generate a negative DC voltage to be applied to a lower electrode of a stage. In a plasma processing performed by using the plasma processing apparatus, a radio frequency power is supplied to generate plasma by exciting a gas within a chamber. Further, the negative DC voltage from the DC power supply is periodically applied to the lower electrode to attract ions in the plasma onto the substrate placed on the stage. A ratio occupied, within each of cycles, by a period during which the DC voltage is applied to the lower electrode is set to be equal to or less than 40%.