Base Plate Contamination Prevention in Polysilicon Reactors

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Solution Overview

Problem

The base plate used in polycrystalline silicon production is difficult to completely clean due to its complex shape and the generation of impurities from the surrounding environment, leading to contamination issues that are not effectively addressed by existing cleaning methods.

Innovation Solution

Implementing an isolation device that covers the base plate after the reactor lid is removed, using a filter unit to supply a large volume of gas, such as 30 to 90 times the device's capacity per hour, to prevent contamination by isolating the space and reducing the introduction of impurities during the production process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the base plate is cleaned manually after silicon rod production, then surface fragments can be removed, but the complex shape and scratches on the base plate make it impossible to completely remove all dirt and contamination

Engineering Contradiction:

Improvecleanliness of base plateVSAvoiddifficulty of cleaning

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent applies preliminary action by isolating the base plate with a cover immediately after the bell jar is removed, preventing contamination before it occurs. The isolation device is prepared and positioned in advance to cover the base plate during the vulnerable period when the reactor is open, rather than attempting to clean contamination after it has settled into scratches and crevices.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If excessive cleaning is performed on the base plate, then more dirt may be removed, but new scratches are created that cause dirt to remain and cleaning tools may be left on the base plate causing contamination

Engineering Contradiction:

Improvecleanliness of base plateVSAvoidnew scratches and tool contamination

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by preventing contamination in the first place through isolation, rather than performing repeated cleaning operations that cause harm. The cover isolates the base plate from the surrounding environment during critical operations, counteracting the contamination tendency without requiring any cleaning action that could create scratches or leave tools behind.

Inventive Principle:

Principle #9Preliminary anti-action

3Manufacturing precision

If a clean room environment is created to prevent contamination, then impurity levels can be reduced, but the cost of creating and maintaining a clean room for multiple Siemens reactors is economically difficult

Engineering Contradiction:

Improveimpurity reductionVSAvoidcost of clean room maintenance

Core Design Contradiction:

Manufacturing precisionVSQuantity of substance

Solution Approach 1:

The patent applies the extraction principle by removing the base plate from the contaminated environment through isolation. Instead of cleaning the entire room or maintaining a clean room atmosphere, the base plate is extracted and protected within the isolated space defined by the cover, separating it from the surrounding contaminated air while leaving the rest of the environment unchanged.

Inventive Principle:

Principle #2Taking out (Extraction)

4Ease of operation

If the reactor remains open for harvesting and setup operations, then workers can access the base plate, but particles generated by worker activities and equipment operations contaminate the base plate

Engineering Contradiction:

Improveaccessibility for harvestingVSAvoidparticle contamination from worker activities

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent applies segmentation by dividing the reactor space into two distinct zones: an isolated zone covered by the cover where the base plate is protected, and an external zone where worker activities occur. This spatial segmentation allows both objectives to be achieved - workers can operate freely in the external zone while the base plate remains protected in the isolated zone.

Inventive Principle:

Principle #1Segmentation

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 significantly reduces contamination on the base plate by isolating it from surrounding impurities, effectively preventing metal and particle contamination, and allows for immediate re-use in polycrystalline silicon production without the need for extensive clean room environments.

Implementation Method 1

the filter unit may blow the gas onto the base plate

Methodology Applied

Scientific EffectGas flow through filter: Filter (physical)

Implementation Method 2

supply, per hour, a gas 30 times or more larger in volume than capacity of the isolation device

Methodology Applied

Scientific EffectGas flow: Convection

Data Source

PatentUS11505862B2Method for preventing contamination of base plate

Publication Date: 2022.11.22 SHIN ETSU CHEMICAL CO LTD

AI summary

A method for preventing contamination of a base plate having a step of, after producing polycrystalline silicon in a reactor having the base plate and a lid covering the base plate, removing the lid from the base plate; and a step of isolating space including the base plate by an isolation device.