Inert Liquid Filter for Semiconductor Gas Separation

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Solution Overview

Problem

In semiconductor processing, the exhaust from CVD and PECVD systems contains unconverted reactants and byproducts that form particles in the fore-line, leading to clogging and maintenance issues, as traditional particle separation methods like water showers are not suitable due to chemical reactions and high water vapor pressure.

Innovation Solution

A liquid filter apparatus using chemically inert liquids with low vapor pressure, such as Fomblin perfluoropolyethers, to separate particles from gas-laden streams in the low-pressure fore-line, preventing chemical reactions and maintaining the semiconductor process integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If water is used to separate particles from gas-laden streams, then particle separation efficiency is improved, but chemical reactions with reactants and high water vapor pressure degrade semiconductor process integrity

Engineering Contradiction:

Improveparticle separation efficiencyVSAvoidchemical reactions and water vapor pressure

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces water with chemically inert liquids such as perfluoropolyether (PFPE) that do not react with semiconductor process gases and have negligible vapor pressure. The inert liquid creates a non-reactive environment that protects the chemical composition of process gases while still enabling effective particle separation through liquid-gas contact mechanisms.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

Solution Approach 2:

The patent changes the physical and chemical parameters of the liquid medium from water to inert liquids with specific properties: negligible vapor pressure (below 10^-7 Torr), chemical inertness, and appropriate viscosity. This parameter change allows the liquid to function as an effective particle separator without introducing harmful chemical reactions or vapor pressure issues.

Inventive Principle:

Principle #35Parameter changes

2Duration of action of stationary object

If mechanical filters are placed in vacuum fore-lines, then vacuum pump life is extended, but particle clogging and maintenance requirements increase

Engineering Contradiction:

Improvevacuum pump lifeVSAvoidmaintenance requirements

Core Design Contradiction:

Duration of action of stationary objectVSEase of repair

Solution Approach 1:

The patent introduces an intermediary liquid medium that captures particles before they reach mechanical filters or vacuum pumps. The inert liquid acts as a mediator that absorbs particles from the gas stream through contact, preventing particle accumulation in mechanical components and reducing maintenance needs while extending pump life.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces mechanical filtration systems with a liquid-based particle separation mechanism. Instead of using mechanical filters that clog and require frequent maintenance, the system uses inert liquid contact to separate particles, eliminating the need for mechanical filtering components in the vacuum fore-line.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If fore-lines and pump exhaust lines are heated to prevent condensation, then condensable reactant deposition is reduced, but liquid/solid plugs form that are costly to clean

Engineering Contradiction:

Improvecondensable reactant depositionVSAvoidcleaning cost and complexity

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent converts the harmful effect of particle formation into a beneficial separation mechanism. By allowing particles to form and then using the inert liquid to capture them, the system transforms the problem of particle deposition into an effective particle removal process, eliminating the need for heating and subsequent cleaning operations.

Inventive Principle:

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

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

Effectively filters particles from semiconductor process gases without degrading the chemical composition, reducing maintenance costs and extending the life of vacuum pumps by preventing clogging, while being compatible with the high-vacuum conditions.

Implementation Method 1

A liquid filter apparatus using chemically inert liquids with low vapor pressure, such as Fomblin perfluoropolyethers, to separate particles from gas-laden streams

Methodology Applied

Scientific EffectLiquid-liquid extraction: Liquid-Liquid Extraction

Implementation Method 2

Suitable filter liquids have a vapor pressure below approximately 10−7 Torr, such as the commercially available Fomblin liquid with its chemical name of perfluoropolyethers (PFPE), which have vapor pressures of approximately 6×10−8 Torr or below

Methodology Applied

Scientific EffectAbsorption (physical): Absorption (physical)

Data Source

PatentUS11786858B2Liquid filter apparatus for gas/solid separation for semiconductor processes

Publication Date: 2023.10.17 EDWARDS VACUUM LLC

AI summary

A liquid filter apparatus for gas/solid separation includes a housing with a filter chamber, a semiconductor process gas inlet, and a process gas outlet. The filter chamber forms a liquid reservoir, and the semiconductor process gas inlet and the process gas outlet are in communication with the filter chamber. The housing further includes a filter liquid inlet and a filter liquid outlet, which are in communication with the liquid reservoir for delivering and removing filter fluid, respectively, to and from the liquid reservoir.