Silicon Crystal Exhaust Pipe Cleaning via Pulsed Inert Gas

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Solution Overview

Problem

The challenge is to effectively remove deposits containing evaporated n-type dopants from exhaust pipes in silicon single crystal production without causing ignition, as these deposits are thick and have strong adhering forces, leading to incomplete burning and potential ignition during cleaning processes.

Innovation Solution

A cleaning method involving a first removal step using inert gas with pulsation to peel and remove the deposit, followed by a second step with atmospheric air without pulsation to burn and remove the remaining deposit, preventing ignition by controlling the peeling force and reaction risks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If atmospheric air is allowed to flow into the exhaust pipe to burn the deposit surface layer, then the deposit can be burned and peeled, but unburned deposit remains due to strong adhering force and thick accumulation

Engineering Contradiction:

Improvedeposit removal completenessVSAvoidcleaning efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The cleaning process is divided into two distinct steps: first using inert gas with pulsation to peel and remove the bulk of the thick deposit, then using atmospheric air without pulsation to burn and remove the remaining deposit. This segmentation allows each step to be optimized for its specific function, achieving both high removal completeness and efficient cleaning.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The inert gas pulsation step is performed as a preliminary action before the atmospheric air burning step. By first peeling and removing the majority of the thick deposit through pulsation, the subsequent burning step can more effectively complete the cleaning without being hindered by the strong adhering force of the original thick deposit layer.

Inventive Principle:

Principle #10Preliminary action

2Strength

If pulsation is applied to atmospheric air to enhance peeling force, then burned substances can be peeled more strongly, but unburned deposit rapidly reacts with atmospheric air and ignites

Engineering Contradiction:

Improvepeeling forceVSAvoidignition risk

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent uses inert gas (such as nitrogen or argon) with pulsation applied during the first cleaning step to peel and remove the bulk of the deposit without creating ignition risk. The inert atmosphere prevents rapid oxidation and ignition of unburned deposit, while the pulsation provides the necessary peeling force to remove thick accumulations effectively.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

Solution Approach 2:

The inert gas acts as an intermediary medium that enables the pulsation peeling process without causing ignition. It mediates between the need for strong peeling force (achieved through pulsation) and the need to prevent ignition (achieved through inert atmosphere), allowing both requirements to be satisfied simultaneously.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of substance

If chamber pressure is increased to prevent dopant evaporation, then dopant loss is reduced, but deposit concentration in exhaust pipe increases leading to thicker deposits

Engineering Contradiction:

Improvedopant evaporation lossVSAvoiddeposit thickness

Core Design Contradiction:

Loss of substanceVSQuantity of substance

Solution Approach 1:

The cleaning method employs parameter changes by switching between different gas types (inert gas with pulsation, then atmospheric air without pulsation) and different pressure conditions. This allows effective removal of the thick deposits that accumulated during high-pressure silicon single crystal production, resolving the contradiction between preventing dopant loss and managing deposit thickness.

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

This method ensures thorough removal of deposits while preventing ignition, improving the productivity of silicon single crystals by avoiding contamination and dislocations during production.

Implementation Method 1

causing an inert gas to which a pulsation is applied to flow into the exhaust pipe to peel and remove the deposit

Methodology Applied

Scientific EffectPulsation: Vibration

Implementation Method 2

causing an atmospheric air to which no pulsation is applied to flow into the exhaust pipe to burn a part of the deposit

Methodology Applied

Scientific EffectCombustion: Combustion

Data Source

PatentUS11426775B2Cleaning method, method for producing silicon single crystal, and cleaning device

Publication Date: 2022.08.30 SUMCO CORP

AI summary

A cleaning method includes a first removal step of causing an inert gas to which a pulsation is applied to flow into an exhaust pipe after a silicon single crystal doped with an n-type dopant is produced, to peel and remove a deposit; and a second removal step of causing an atmospheric air to which no pulsation is applied to flow into the exhaust pipe through a chamber to burn a part of the deposit with the atmospheric air, the part being not removable in the first removal step, and peel and remove a burned substance of the deposit.