Mean Free Path Measurement via Charged Particle Decay

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Solution Overview

Problem

Current methods for measuring the mean free path in gas atmospheres are indirect, labor-intensive, and complex, especially when dealing with mixed gases, making it difficult to obtain accurate and simple measurements, which is crucial for processes like sputtering and dry etching where ion beam divergence and vacuum degree are critical.

Innovation Solution

A device and method that directly measures the mean free path of charged particles by generating charged particles, detecting their decay at different flight distances, and calculating the mean free path from the ratio of detected particles, eliminating the need for complex calculations and separate mass analysis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If indirect calculation methods are used to obtain mean free path from temperature and particle diameter, then measurement can be performed, but the process becomes labor-intensive and complex especially for mixed gases

Engineering Contradiction:

Improvemean free path measurement accuracyVSAvoidmeasurement process complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical/calculation-based indirect measurement system with a direct detection system. Instead of calculating mean free path from temperature and particle diameter measurements, the invention uses a detector to directly count charged particles at different flight distances, eliminating complex calculations and mass spectrometer requirements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The measurement system uses the charged particles themselves to provide measurement information. By detecting the decay of charged particle numbers over flight distance, the system obtains mean free path data directly from the particles' behavior rather than requiring external reference measurements or complex conversion calculations.

Inventive Principle:

Principle #25Self-service

2Measurement precision

If mass spectrometers and separate component analysis are used for mixed gases, then accurate mean free path can be obtained, but the measurement process becomes extremely labor-intensive

Engineering Contradiction:

Improvemean free path measurement accuracyVSAvoidmeasurement time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces the time-consuming mass spectrometer analysis system with a direct particle counting detection system. The detector measures charged particle decay over flight distance without requiring identification of gas components, eliminating the need for separate mass spectral analysis of mixed gas compositions.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If conventional vacuum gauges are used, then vacuum degree can be measured, but measurements are limited to specific ranges and require calibration

Engineering Contradiction:

Improvevacuum measurement rangeVSAvoidvacuum degree measurement accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent changes the measurement parameter from pressure-based detection to charged particle decay detection. By measuring the decay of charged particle numbers over flight distance, the system obtains mean free path information that directly reflects vacuum degree across a wide range without requiring gauge calibration or being limited to specific pressure ranges.

Inventive Principle:

Principle #35Parameter changes

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 accurate and simple measurement of the mean free path, improving the control of ion beam divergence and vacuum degree, enhancing processing precision in sputtering and dry etching, and allowing for accurate vacuum degree measurement across a wide range without the limitations of existing gauges.

Implementation Method 1

an average distance in which a particle can move without collision is called a mean free path

Methodology Applied

Scientific EffectMean free path:

Implementation Method 2

detecting a number of second charged particles having a second flight distance longer than the first flight distance, and a calculation means for calculating the mean free path from a ratio between the numbers of the first and second charged particles

Methodology Applied

Scientific EffectCharged particle decay:

Data Source

PatentUS8436295B2Device for measuring mean free path, vacuum gauge, and method for measuring mean free path

Publication Date: 2013.05.07 CANON ANELVA CORP

AI summary

The present invention provides a device for measuring a mean free path capable of measuring directly the mean free path of a charged particle, a vacuum gauge, and a method for measuring a mean free path. The device for measuring a mean free path according to one embodiment of the invention includes an ion source for generating an ion, a collector (24a) for detecting the number of first charged particles being charged particles having a first flight distance L1 that is a flight distance of zero or more from the ion source, and a collector (24b) for detecting the number of second charged particles having a second flight distance longer than the first flight distance. The control part of the device calculates the mean free path from a ratio between the numbers of the first and second charged particles.