Polycrystalline Silicon Lump Packaging to Reduce Storage Stains
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Solution Overview
Problem
Existing methods for removing acid solution components from polycrystalline silicon lumps are insufficient in preventing stains during long-term storage and harsh environmental conditions, particularly due to residual nitrate ions, which lead to defects in single crystal silicon wafers.
Innovation Solution
The packaging body is filled with polycrystalline silicon lumps having a surface metal concentration of 1000 pptw or less and a nitrate ion amount of 50 μg/L or less within the filling void, achieved through acid cleaning with nitrohydrofluoric acid at 100° C. or higher and controlled filling conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If acid cleaning with nitrohydrofluoric acid is performed to remove metal impurities, then surface metal concentration is reduced, but residual nitrate ions remain and cause stains during storage
Solution Approach 1:
The patent applies parameter changes by controlling the nitrate ion amount in the packaging body to 50 μg/L or less and the surface metal concentration to 1000 pptw or less. These specific parameter thresholds resolve the contradiction by establishing quantitative standards that prevent stain occurrence while maintaining effective metal impurity removal through acid cleaning.
Solution Approach 2:
The patent creates an inert environment by strictly controlling the nitrate ion concentration in the packaging body to 50 μg/L or less. This controlled environment prevents the chemical reactions between residual acid components and oxygen that would otherwise cause stain formation during storage, effectively isolating the polycrystalline silicon lumps from harmful chemical interactions.
2Reliability
If polycrystalline silicon lumps are stored in packaging body for long period or exposed to high temperature and high humidity, then metal impurities are removed, but stains occur on the surface
Solution Approach 1:
The patent applies preliminary action by controlling the nitrate ion amount to 50 μg/L or less before storage begins. This pre-storage preparation ensures that residual acid components are minimized in advance, preventing stain formation that would otherwise occur during long-term storage or exposure to high temperature and humidity conditions.
Solution Approach 2:
The patent uses parameter changes by establishing the nitrate ion amount threshold of 50 μg/L or less and surface metal concentration of 1000 pptw or less. These parameter controls ensure that the polycrystalline silicon lumps maintain their quality throughout storage and transportation, even under harsh environmental conditions.
3Ease of manufacture
If acid solution components permeate into cracks and fissures, then metal impurities are dissolved, but residual acid components combine with oxygen to cause stains
Solution Approach 1:
The patent applies parameter changes by controlling the nitrate ion amount in the packaging body to 50 μg/L or less and surface metal concentration to 1000 pptw or less. These quantitative parameters balance the need for metal impurity dissolution during acid cleaning with the requirement to prevent stain formation from residual acid components.
Solution Approach 2:
The patent implements feedback by measuring and controlling the nitrate ion amount and surface metal concentration to specific thresholds. This feedback mechanism ensures that acid cleaning is performed sufficiently to remove metal impurities while preventing excessive acid residue that would cause stains during subsequent storage.
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 approach significantly reduces stain occurrence on the silicon lumps, ensuring high-quality single crystal silicon production by preventing defects in wafers even under harsh storage conditions.
Implementation Method 1
hydrofluoric acid has effects of satisfactorily dissolving an oxide film formed on the surface of the crushed polycrystalline silicon lumps, and also dissolving various metals and oxides thereof adhering to the oxide film
Implementation Method 2
nitric acid exerts effects of oxidizing the polycrystalline silicon to form an oxide film on the surface of the crushed polycrystalline silicon lumps
Implementation Method 3
dissolving various metals and oxides thereof adhering to the oxide film
Data Source
AI summary
A polycrystalline silicon lump packaging body is a packaging body in which the resin bag is filled with the polycrystalline silicon lumps having a surface metal concentration of 1000 pptw or less, in which a nitrate ion amount and preferably a fluorine ion amount present inside the packaging body are each 50 μg/L or less with respect to a filling void of the polycrystalline silicon lumps formed when the packaging body is left at 25° C. under 1 atm.