Plasma Sheath Voltage Control for Narrow Ion Energy Distribution
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Solution Overview
Problem
Current methods for controlling the ion energy distribution function (IEDF) during plasma processing are inefficient, relying on iteration loops that are slow and often result in inaccurate plasma parameter estimation, leading to non-convergence and broadened IEDF.
Innovation Solution
The implementation of a method that introduces a voltage to an electrode using a main pulser coupled with an IEDF width control module, measuring current and voltage or voltage derivatives, and calculating ion current and capacitance to determine setpoints for DC voltage adjustments, allowing for direct control of IEDF width without iteration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If iterative control loops are used to control IEDF, then control coverage is improved, but control speed and precision deteriorate due to slow convergence and inaccurate parameter estimation
Solution Approach 1:
The patent replaces the mechanical iterative control loop system with a direct calculation system based on measured voltage and current derivatives. Instead of using repeated trial-and-error iterations to converge on IEDF parameters, the system directly computes ion current and capacitance values from instantaneous measurements, eliminating the time-consuming iterative process while maintaining comprehensive control capability
Solution Approach 2:
The patent introduces voltage derivative and current derivative measurements as intermediary parameters that directly reveal IEDF characteristics. By measuring dV/dt and dI/dt, the system obtains immediate information about ion current and capacitance without requiring iterative inference, serving as a mediator between the applied voltage and the resulting IEDF state
2Adaptability or versatility
If iterative control loops are used to control IEDF, then control coverage is improved, but manufacturing precision deteriorates due to inaccurate plasma parameter estimation
Solution Approach 1:
The patent replaces the imprecise iterative estimation process with direct calculation methods that compute ion current and capacitance from measured voltage and current derivatives. This substitution eliminates the accumulation of estimation errors that occur in iterative loops, providing precise IEDF control while maintaining broad adaptability
Solution Approach 2:
The system uses the plasma process itself to generate the measurement signals needed for control. The voltage applied to the electrode and the resulting current are directly measured and used to calculate IEDF parameters, allowing the system to self-determine its state without external interference or iterative guessing
3Extent of automation
If ion current charges the substrate to alter substrate potential, then plasma sheath voltage is affected, but IEDF broadening occurs as an unwanted side effect
Solution Approach 1:
The patent implements feedback control by measuring the current through the IEDF width control module and using its derivative to determine ion current and capacitance. This feedback mechanism allows the system to detect and compensate for substrate potential changes caused by ion current charging, maintaining narrow IEDF width while enabling automated substrate potential control
Solution Approach 2:
The system takes preliminary anti-action by measuring voltage and current derivatives before IEDF broadening can occur. By detecting the tendencies of substrate potential change through derivative measurements, the system can preemptively adjust control parameters to prevent unwanted IEDF broadening while maintaining automated control
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 enables faster achievement of a desired IEDF state, such as a narrow IEDF, by directly determining ion current and compensation current, improving control precision and speed compared to state-of-the-art methods.
Implementation Method 1
When periodic alternating voltage is applied to electrode(s) of a chamber, a plasma sheath can develop above the substrate. The ions flowing towards the substrate are accelerated by the plasma sheath voltage
Implementation Method 2
The ions flowing towards the substrate are accelerated by the plasma sheath voltage which correlates with the voltage applied to the electrode
Implementation Method 3
measuring a current of the IEDF width control module and a voltage or a voltage derivative of the IEDF width control module
Implementation Method 4
adjusting the DC voltage of the main pulser, the voltage or voltage derivative of the IEDF width control module, or both, to the determined setpoints to control the width of the IEDF
Data Source
AI summary
Embodiments of the present disclosure generally relate to apparatus and methods for controlling an ion energy distribution during plasma processing. In an embodiment, the apparatus includes a substrate support that has a body having a substrate electrode for applying a substrate voltage to a substrate, and an edge ring electrode embedded for applying an edge ring voltage to an edge ring. The apparatus further includes a substrate voltage control circuit coupled to the substrate electrode, and an edge ring voltage control circuit coupled to the edge ring electrode. The substrate electrode, edge ring electrode, or both are coupled to a power module configured to actively control an energy distribution function width of ions reaching the substrate, edge ring, or both. Methods for controlling an energy distribution function width of ions during substrate processing are also described.