Plasma Endpoint Detection Using RF Harmonic Tracking

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Solution Overview

Problem

Existing plasma processing technologies face issues with inaccurate endpoint detection due to dependency on physical parameters, leading to unstable plasma, equipment damage, and increased maintenance costs, as well as safety hazards from harmonics.

Innovation Solution

A plasma processing control system that utilizes a transducer assembly to track harmonics associated with voltage and current, and spectrum analyzers to analyze these harmonics using RF spectroscopy, allowing for precise endpoint detection independent of physical parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If single frequency RF energy is delivered to plasma, then plasma processing can be performed, but harmonics are generated causing EMI/RFI, unstable plasma, equipment damage, and safety hazards

Engineering Contradiction:

Improveplasma processing capabilityVSAvoidharmonics

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful harmonics generated by plasma processing into a useful endpoint detection signal. By monitoring the frequency spectrum and detecting changes in harmonic content, the system determines when the plasma process has reached its endpoint, transforming a harmful byproduct into a beneficial control mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The system implements real-time feedback by continuously monitoring the RF frequency spectrum during plasma processing. The spectrum analyzer detects changes in harmonic content and provides feedback signals that indicate process endpoint, allowing for automatic process termination or adjustment to prevent equipment damage and ensure consistent results.

Inventive Principle:

Principle #23Feedback

2Duration of action of stationary object

If plasma processing continues without precise endpoint detection, then processing can be maintained, but equipment damage, downtime, and increased maintenance costs occur

Engineering Contradiction:

Improveplasma processing durationVSAvoidequipment reliability

Core Design Contradiction:

Duration of action of stationary objectVSReliability

Solution Approach 1:

The system performs preliminary detection of endpoint conditions by continuously analyzing the frequency spectrum before actual endpoint is reached. By monitoring harmonic content changes in advance, the system can prepare for process termination, ensuring equipment is protected before damage occurs and maintaining reliable operation.

Inventive Principle:

Principle #10Preliminary action

3Extent of automation

If traditional endpoint detection methods are used, then process control is attempted, but detection accuracy is poor due to dependency on physical parameters

Engineering Contradiction:

Improveprocess control automationVSAvoidendpoint detection accuracy

Core Design Contradiction:

Extent of automationVSMeasurement precision

Solution Approach 1:

The patent replaces traditional physical parameter-based endpoint detection methods with electromagnetic spectrum analysis. By using a spectrum analyzer to monitor RF frequency content and harmonic changes, the system achieves more accurate and reliable endpoint detection that is not dependent on physical parameters such as optical properties or electrical impedance that can vary with material composition.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Accurate endpoint detection ensures consistent and repeatable plasma processing, reduces downtime and energy consumption, enhances safety, and lowers maintenance costs by optimizing process control.

Implementation Method 1

a power source such as a Radio Frequency (RF) power source, and a substrate holder. The plasma processing chamber is an enclosure that receives a supply of gas via the gas delivery system that is ionized by the electromagnetic waves produced by the power source

Methodology Applied

Scientific EffectElectromagnetic radiation: Electromagnetic Induction

Implementation Method 2

the plasma environments are intrinsically nonlinear which means that if a single frequency energy is delivered to the plasma, then some of the energy will be frequency shifting to harmonics of the incident single frequency

Methodology Applied

Scientific EffectHarmonic generation:

Implementation Method 3

A plasma processing control system that utilizes a transducer assembly to track harmonics associated with voltage and current, and spectrum analyzers to analyze these harmonics using RF spectroscopy

Methodology Applied

Scientific EffectRF spectroscopy:

Data Source

PatentUS12562358B2System and method for detecting endpoint in plasma processing

Publication Date: 2026.02.24 HORIBA STEC CO LTD

AI summary

A plasma processing control method for detecting an endpoint and controlling plasma processing is disclosed. The plasma processing control method includes tracking one or more harmonics that are produced due to nonlinearity of an impedance of a plasma environment. The one or more harmonics are associated with voltage, current, or a combination thereof. The plasma processing control method further includes analyzing the tracked one or more harmonics and detecting an endpoint of plasma processing based on the analysis of the tracked one or more harmonics. Thereafter, the plasma processing control method includes stopping the plasma processing based on the detected endpoint.