Inductive RF Plasma Sensors for Fast Density Uniformity Detection
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Solution Overview
Problem
RF plasma processing systems face challenges in maintaining control over plasma density uniformity within reaction chambers, leading to non-uniform etch rates and yield issues in semiconductor manufacturing, as existing monitoring techniques are slow and insensitive to rapid changes in plasma conditions.
Innovation Solution
The implementation of high-bandwidth sensors mounted on various components of the RF plasma processing system, including electrodes and pedestals, to detect and analyze RF surface waves, allowing for rapid determination of plasma density uniformity and asymmetry by monitoring the amplitudes and phases of fundamental and harmonic frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional probes or emission spectroscopy are used to monitor plasma density, then plasma density can be measured, but the response time is too slow (milliseconds or more) to detect rapid changes in plasma conditions
Solution Approach 1:
The patent replaces traditional mechanical/electronic probes with inductive sensors that detect plasma density through electromagnetic induction. The sensors measure RF voltage and current signals induced by plasma, providing non-contact, high-speed detection without the response time limitations of probe-based systems.
Solution Approach 2:
The patent introduces RF surface waves as an intermediary to transfer plasma density information to the sensors. The sensors detect changes in RF voltage and current caused by plasma density variations, enabling indirect but rapid measurement of plasma conditions without direct probe exposure.
2Reliability
If probes are used to monitor plasma density, then plasma density can be detected, but the probes require coatings and active electronics that complicate the system and reduce reliability in harsh plasma environments
Solution Approach 1:
The patent replaces vulnerable electronic probes with passive inductive sensors that detect plasma density through electromagnetic coupling. The sensors contain no exposed electronics or coatings, eliminating the reliability issues and complexity associated with protecting components in harsh plasma environments.
Solution Approach 2:
The patent extracts the sensing function from the plasma environment by using inductive coupling through chamber walls or windows. The sensors remain outside the harsh plasma zone while still detecting plasma density changes, removing the need for coatings and protective measures.
3Measurement precision
If emission spectroscopy is used to determine plasma density profile, then plasma density distribution can be inferred, but multiple lines of sight and complicated analysis are required making the system costly and complex
Solution Approach 1:
The patent replaces complex optical emission spectroscopy systems with electromagnetic induction-based sensors. The inductive sensors directly measure RF voltage and current signals that correlate with plasma density, eliminating the need for multiple optical lines of sight and complex spectral analysis algorithms.
Solution Approach 2:
The patent changes the measurement parameter from optical emission intensity to RF voltage and current induction. This parameter change enables direct, single-point measurement of plasma density without the complex multi-line-of-sight optical systems required for emission spectroscopy.
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
Enables prompt and accurate detection of plasma density deviations, enabling corrective actions within milliseconds to maintain process uniformity and prevent irreversible wafer deviations, thereby improving yield and feature precision in semiconductor fabrication.
Implementation Method 1
inductive sensor that senses RF voltage and current signals from RF surface waves
Data Source
AI summary
A broad-band sensor for a radio frequency plasma processing system that includes a reaction chamber housing an electrode within a vacuum processing environment. The sensor includes an inductive pickup positioned in the vacuum processing environment proximate to the electrode. The inductive pickup includes a wire formed into a loop extending in an azimuthal direction about a symmetry axis of the reaction chamber. A lead carrying an electric signal from the inductive pickup extends through a vacuum wall of the reaction chamber outside the vacuum processing environment. An attenuator circuit including an electrical resistance bridge couples the lead to a signal carrier extending outside the vacuum processing environment. The broad-band sensor has radio frequency detection capability for measuring electromagnetic surface modes within the plasma chamber and coupling the measured electromagnetic surface modes to the signal carrier.