Pulsed Voltage Feedback Loop for Mono-Energetic IEDF Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor manufacturing, maintaining a consistent sheath voltage in plasma processing chambers is challenging due to real-time changes in plasma density and chamber conditions, leading to difficulties in controlling the Ion Energy Distribution Function (IEDF) and achieving precise feature profiles in high aspect ratio etching processes.
Innovation Solution
A closed feedback loop system is implemented, using a data acquisition system with conditioning circuits and a fast data acquisition module to analyze and adjust pulsed voltage waveforms in real-time, ensuring a nearly constant sheath voltage and a single-peak IEDF through a pulsed voltage waveform generator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a lower frequency RF bias generator is used to achieve higher self-bias voltages, then the etch anisotropy is improved, but the ion energy distribution becomes bimodal causing bowing of etched feature walls
Solution Approach 1:
The patent applies periodic pulsed voltage waveforms to the substrate electrode instead of continuous RF bias. By controlling the pulse width, frequency, and duty cycle, the system achieves high self-bias voltages while maintaining a mono-energetic ion distribution (single-peak IEDF), thereby preventing feature wall bowing while preserving etch anisotropy
Solution Approach 2:
The patent changes the voltage waveform parameters from sinusoidal RF to pulsed DC waveforms with controllable rise time, pulse width, and frequency. This parameter transformation allows independent control of ion energy distribution, enabling high anisotropy with mono-energetic ion bombardment
2Adaptability or versatility
If real-time changes in plasma density and chamber conditions occur, then the plasma processing is adaptable to varying loads, but the sheath voltage becomes difficult to maintain consistently
Solution Approach 1:
The patent implements a feedback control system using a data acquisition system to monitor the actual voltage waveform and a control system to adjust the pulsed voltage waveform generator in real-time. This closed-loop feedback maintains consistent sheath voltage despite variations in plasma density and chamber conditions
Solution Approach 2:
The patent uses dynamically adjustable pulsed voltage waveforms with variable pulse width, frequency, and amplitude that can be modified in real-time through feedback control, allowing the system to adapt to changing plasma conditions while maintaining stable sheath voltage
3Measurement precision
If a data acquisition system with conditioning circuits is used to analyze pulsed voltage waveforms, then the waveform control precision is improved, but the device complexity increases
Solution Approach 1:
The patent introduces conditioning circuits as intermediary components between the high-voltage pulsed waveform source and the data acquisition system. These circuits condition the harsh high-voltage signals into suitable forms for precise measurement, enabling accurate waveform analysis without directly exposing the measurement system to extreme conditions
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 precise control of the IEDF and feature profiles, maintaining a consistent sheath voltage for up to 90% of the processing time, resulting in repeatable and desirable mono-energetic ion distributions for improved etch anisotropy and feature control.
Implementation Method 1
The power electrode is capacitively coupled to the plasma of a processing system through a thick layer of dielectric material
Implementation Method 2
The application of RF voltage to the power electrode causes an electron-repelling plasma sheath (also referred to as the 'cathode sheath') to form over a processing surface of a substrate
Implementation Method 3
ions from the plasma are accelerated towards a surface of a substrate to form openings in a material layer
Implementation Method 4
a first conditioning circuit configured to generate a first conditioned voltage waveform from a first input voltage waveform
Implementation Method 5
a fast data acquisition module including a first acquisition channel that is electrically coupled to the first conditioning circuit
Data Source
AI summary
Embodiments of this disclosure describe a feedback loop that can be used to maintain a nearly constant sheath voltage and thus creating a mono-energetic IEDF at the surface of the substrate. The system described herein consequently enables a precise control over the shape of IEDF and the profile of the features formed in the surface of the substrate.