Plasma Bias Control for Narrow Ion Energy Distribution
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Solution Overview
Problem
Current methods for controlling ion energy distribution during plasma processing are inefficient, relying on iteration loops that are slow and often non-convergent, leading to inaccurate estimation of plasma parameters and broadening of the ion energy distribution function (IEDF).
Innovation Solution
A method and apparatus that utilize a single loop process to control the ion energy distribution by measuring current and voltage derivatives, calculating ion current and capacitance, and adjusting setpoints for the DC voltage or current to actively control the width of the IEDF, using a pulsed DC power delivery system with a main pulser and power module to modulate the ion energy distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If periodic alternating voltage is applied to electrode to control ion energy, then ion acceleration is achieved, but ion energy distribution broadens due to substrate charging
Solution Approach 1:
The patent implements a feedback control system where the substrate potential is continuously monitored and used to adjust the applied voltage waveform. The controller modifies the periodic alternating voltage in real-time based on measured substrate charging effects, creating a closed-loop system that compensates for IEDF broadening while maintaining ion acceleration
Solution Approach 2:
The patent dynamically changes voltage waveform parameters (amplitude, frequency, duty cycle) to optimize ion energy distribution. By adjusting these parameters in response to substrate charging conditions, the system maintains narrow IEDF width while achieving desired ion acceleration energies
2Manufacturing precision
If iteration loops are used to control ion energy distribution, then control capability is provided, but processing efficiency decreases due to slow convergence
Solution Approach 1:
The patent pre-calculates and stores optimal voltage waveform parameters for different substrate charging conditions in lookup tables. Instead of performing iterative calculations during processing, the system directly retrieves pre-computed control parameters, eliminating slow iteration loops while maintaining precise IEDF control
Solution Approach 2:
The patent uses simplified empirical models and approximate calculations that provide sufficient accuracy for real-time control without requiring computationally intensive iterative solutions. These lightweight calculation methods enable fast response times while achieving the necessary control precision
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 allows for faster and more precise control of the IEDF, achieving a narrower distribution compared to sine wave RF biases and avoiding the broadening caused by ion current, thereby enhancing substrate processing efficiency.
Implementation Method 1
The ions flowing towards the substrate are accelerated by the plasma sheath voltage which correlates with the voltage applied to the electrode
Implementation Method 2
when periodic alternating voltage is applied to electrode(s) of a chamber, a plasma sheath can develop above the substrate
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.