Silicon Powder Molding for Czochralski Single Crystal Loading
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Solution Overview
Problem
The small particle size of primary polycrystalline silicon powder results in low loading density, making it unsuitable for direct use in Czochralski single crystal pulling technology.
Innovation Solution
A silicon powder molding method involving placing a mold filled with silicon powder under a controlled pressure condition, maintaining the pressure for a specific duration to form a silicon block, which can then be used in Czochralski single crystal pulling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon powder with small particle size is used, then the material can be processed easily, but the loading density becomes low
Solution Approach 1:
The patent applies parameter changes by controlling the particle size distribution of silicon powder through classification processes. By adjusting and optimizing the particle size parameters (keeping d10-d90 within 0.1-1000 μm) and controlling the content of different particle size ranges, the patent achieves both easy processing and improved loading density, resolving the contradiction between ease of manufacture and quantity of substance.
2Device complexity
If silicon powder is directly loaded into CZ furnace, then the process is simple, but the continuous feeding and crystal pulling process cannot be performed
Solution Approach 1:
The patent applies preliminary action by pre-processing the silicon powder through classification and molding before it is loaded into the CZ furnace. The silicon powder is classified by particle size and molded into blocks with controlled density and uniformity. This preliminary preparation enables the silicon material to be suitable for continuous feeding and crystal pulling processes, transforming simple direct loading into a preparatory process that enables complex continuous operation.
3Quantity of substance
If high pressure is applied to compact silicon powder, then the loading density increases, but the mold material wears out faster
Solution Approach 1:
The patent applies parameter changes by optimizing the pressure parameters during the molding process. By controlling the pressure to be within 50-600 MPa and the pressure time to be within 1-15 minutes, the patent achieves the desired loading density while preventing excessive mold wear. This parameter optimization resolves the contradiction between increasing loading density and maintaining mold service life.
Solution Approach 2:
The patent applies composite materials by selecting mold materials with specific properties (such as polyurethane with density 1.00-1.01 g/cm³) that can withstand the required pressure ranges while maintaining adequate wear resistance. The composite approach of selecting appropriate mold material properties allows the system to achieve high loading density without excessive mold degradation.
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
The method increases the loading density of silicon blocks to 0.18 g/cm3 to 0.25 g/cm3, enabling their direct use in Czochralski single crystal pulling and improving the efficiency of the process.
Implementation Method 1
a medium applying the first pressure P1 is a liquid
Implementation Method 2
placing a mold filled with silicon powder under a first pressure P1 condition, maintaining the first pressure condition P1 for a continuous duration of a first pressure time T1
Data Source
AI summary
A silicon powder molding method, a silicon block, and their applications in the field of single crystal growth technology are provided. The silicon powder molding method of this application includes the following steps: placing a mold filled with silicon powder under a first pressure P1 condition, maintaining the first pressure condition P1 for a continuous duration of a first pressure time T1, and satisfying 50 MPa≤P1≤600 MPa, 7 minutes ≤T1≤15 minutes to obtain a silicon block. A medium applying the first pressure P1 is a liquid. Through pressure control, the molded silicon block is easily removed from the mold without breaking and generating dust. The silicon block is easy to crush when filling and has a controllable particle size distribution after crushing. The silicon block can be directly used for the production of Czochralski grown single crystals, increasing a loading density to 0.18 g/cm3˜0.25 g/cm3.