Pulsed Voltage Compensation for Stable Plasma Sheath Control
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Solution Overview
Problem
Existing plasma-assisted etching processes struggle to reliably form high aspect ratio features due to challenges in controlling the plasma sheath and ion energy distribution, particularly with voltage decay during the ion current stage, which affects the anisotropy and within-substrate processing uniformity.
Innovation Solution
A method and system for generating a compensated voltage waveform by detecting characteristics of the plasma sheath using sensors, calculating a compensation factor based on voltage decay and sheath coupling values, and adjusting the waveform to maintain a constant sheath potential during plasma processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high voltage DC pulses are delivered to control the plasma sheath, then ion energy control is improved, but voltage decay during the ion current stage causes undesirable ion energy distribution
Solution Approach 1:
The system measures the actual substrate potential during plasma processing and uses this feedback to dynamically adjust the pulsed voltage waveform. The controller modifies the compensation waveform in real-time based on measured voltage decay, ensuring consistent ion energy delivery despite varying plasma conditions.
Solution Approach 2:
The system dynamically changes the voltage waveform parameters (amplitude, duration, shape) to compensate for voltage decay. By adjusting the compensation waveform parameters based on measured substrate potential, the system maintains desired ion energy distribution across varying process conditions.
2Manufacturing precision
If voltage compensation is applied to maintain constant sheath potential, then processing uniformity is improved, but the system complexity increases
Solution Approach 1:
The system uses the plasma processing chamber's own measurements (substrate potential) to generate its own compensation waveform. The measured substrate potential directly informs the compensation waveform generation, allowing the system to self-regulate without external intervention or complex external control systems.
Solution Approach 2:
The controller performs multiple functions: it generates the initial pulsed voltage waveform, measures the substrate potential, calculates the compensation waveform, and delivers the compensated waveform. This multi-functionality reduces the need for separate dedicated components for each function.
3Measurement precision
If sensors are used to detect plasma sheath characteristics, then control precision is improved, but the measurement and detection difficulty increases
Solution Approach 1:
The system uses an intermediary measurement approach by measuring substrate potential through the electrostatic chuck's electrical characteristics rather than directly measuring the plasma sheath. This indirect measurement method simplifies the detection process while providing sufficient information for compensation.
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 solution enables fine-tuning and control over the plasma sheath, resulting in a narrower ion energy distribution function and improved uniformity in forming high aspect ratio features.
Implementation Method 1
the substrate is positioned on an electrostatic chuck (ESC) disposed in a processing chamber
Implementation Method 2
ions are accelerated from the plasma towards the substrate across a plasma sheath
Implementation Method 3
a plasma is formed over the substrate
Data Source
AI summary
Embodiments provided herein generally include apparatus, e.g., plasma processing systems, and methods for the plasma processing of a substrate in a processing chamber. Some embodiments are directed to a method for waveform generation, which generally includes delivering a first waveform with an associated setpoint from an energy source; detecting at least one characteristic of the first waveform; estimating a voltage decay during a portion of a pulse during the first waveform; calculating a compensation factor; and adjusting the at least one characteristic using the compensation factor to adjust a voltage decay.