Particle measuring method and detection liquid
Inventors
Tomita, Hiroshi • Hayashi, Hidekazu • Shiobara, Eishi • Kondo, Kaoru • TABUCHI, Takuya • BANDO, Kazuna • KONDO, Sota
Assignees
Publication Number
US-11112344-B2
Publication Date
2021-09-07
Expiration Date
2040-03-03
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Abstract
According to one embodiment, a particle measuring method is disclosed. The method includes irradiating a detection liquid with light. The detection liquid contains methyl salicylate. The method further includes converting scattered light from the detection liquid into an electric signal by using photoelectric conversion after irradiating the detection liquid with the light. The method further includes performing a particle measurement on the detection liquid by using the electric signal.
Core Innovation
The invention relates to a particle measuring method and detection liquid, specifically for measuring particles in a liquid such as fluororesin particles generated from parts in contact with ultrapure liquids used in semiconductor manufacturing. The method utilizes light scattering and photoelectric conversion to detect and measure particles dispersed in a detection liquid containing methyl salicylate.
The problem being solved is the difficulty in detecting fine fluororesin particles in conventional ultrapure water due to the close refractive indices between the particles and the solvent, which reduces scattered light intensity and measurement sensitivity. By using methyl salicylate as the solvent in the detection liquid, which possesses a higher refractive index, the scattered light intensity and hence detection sensitivity for fluororesin particles is improved.
Additionally, the invention addresses the issue of clouding in methyl salicylate when exposed to atmospheric moisture, which increases background light scattering and reduces detection sensitivity. The solution involves nitrogen gas sealing the tank storing methyl salicylate to suppress moisture ingress and maintain stable measurement conditions.
Claims Coverage
The patent contains one independent claim outlining a particle measuring method utilizing methyl salicylate as the solvent, with additional features concerning particle measurement techniques and system configurations.
Particle measuring method using methyl salicylate solvent
Irradiating a detection liquid, whose solvent is methyl salicylate, with light; converting scattered light from particles in the detection liquid into an electric signal through photoelectric conversion; performing particle measurement on the detection liquid using the electric signal.
Particle measurement of fluororesin particles including PFA or PTFE
Measurement of particles comprising fluororesin such as perfluoroalkoxy alkane (PFA) or polytetrafluoroethylene (PTFE) in the detection liquid.
Particle measurement based on pulse waves in electric signal
Calculating the number of particles based on the number of pulse waves in the electric signal derived from scattered light.
Particle size calculation based on pulse wave amplitude
Determining particle size by analyzing amplitude of pulse waves in the electric signal.
Particle size and distribution measurement using intensity changes from Brownian movement
Calculating particle size or particle size distribution by analyzing intensity changes in the electric signal caused by Brownian motion of particles in the liquid.
Particle size and distribution measurement using particle displacement from Brownian movement
Calculating particle size or particle size distribution based on the amount of particle displacement resulting from Brownian movement.
Use of laser light and photomultiplier tube for detection
Using laser light as the irradiation source and photomultiplier tube for converting scattered light into electric signals.
Flowing detection liquid through semiconductor manufacturing parts
Making the detection liquid flow through parts containing fluororesin particles, such as pipes, joints, valves, pumps, or filters used in semiconductor device manufacturing.
Storage of detection liquid under nitrogen gas sealing
Storing the detection liquid containing methyl salicylate in a tank subjected to nitrogen gas sealing before it flows through the parts to prevent moisture contamination and clouding.
The claims collectively cover a particle measuring method employing methyl salicylate as a detection liquid solvent, particle measurement techniques utilizing photoelectric conversion and Brownian motion analysis, and system configurations including nitrogen sealing storage and application to semiconductor manufacturing parts containing fluororesin particles.
Stated Advantages
Improved detection sensitivity for fine fluororesin particles due to increased refractive index difference between solvent and particles.
Enhanced ability to detect smaller particles compared to conventional ultrapure water solvents.
Suppression of clouding and background light scattering by nitrogen gas sealing to prevent moisture ingress into methyl salicylate.
Safety and thermal stability advantages of methyl salicylate as a detection solvent compared to other high refractive index solvents.
Documented Applications
Measuring particles generated from parts (pipes, joints, valves, pumps, filters) in contact with ultrapure liquid used in semiconductor device manufacturing.
Use of the particle measuring method with liquids for functional coating films such as resist.
Application in liquid-borne particle measuring systems for evaluating particle generation from fluororesin-containing parts in semiconductor manufacturing.
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