Layered Silicon Charging for Single Crystal Furnace Stability
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Solution Overview
Problem
The existing process for charging a crucible in a Czochralski single crystal furnace lacks a reasonable method, leading to issues with single crystal growth due to the purity and particle size of raw polycrystalline silicon powder, which causes breakage and inefficiencies in crystal pulling.
Innovation Solution
A charging method involving multiple layers of silicon material with specific thickness and particle size ranges is used, where the first material layer is covered by a second layer during vacuuming, and a third layer is added to optimize crucible filling, ensuring stable and efficient charging. This method includes vacuuming and pressure relief steps to prevent material loss and ensure proper crucible preparation for single crystal growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If raw polycrystalline silicon powder with small particle size and ppm level purity is used for charging the crucible, then the charging process can be simplified, but the single crystal growth is affected and broken bracts occur easily
Solution Approach 1:
The silicon material is divided into three distinct layers with different particle sizes: first layer (0.1-1000 μm) at the bottom, second layer (1-3 mm) in the middle, and third layer (10-70 mm) on top. This segmentation allows each layer to serve specific functions - the finer first layer ensures complete filling and adhesion to the crucible bottom, the second layer provides structural support and covers the first layer during vacuuming, and the third layer completes the charging. This resolves the contradiction by maintaining charging simplicity while ensuring reliable single crystal growth through optimized material distribution.
Solution Approach 2:
Different regions of the crucible are filled with silicon material of locally optimized particle sizes. The bottom region (first layer) uses finer particles for complete filling and adhesion, the middle region (second layer) uses medium particles for structural support and vacuum sealing, and the top region (third layer) uses coarser particles for completing the charge. This local quality differentiation ensures that each region's material properties are optimized for its specific function, resolving the contradiction between charging ease and crystal growth reliability.
2Ease of operation
If raw polycrystalline silicon powder is charged directly into the crucible without covering, then the charging operation is simpler, but material loss occurs during vacuuming
Solution Approach 1:
The second layer of silicon material (1-3 mm particle size) is placed on top of the first layer before vacuuming begins, serving as a protective cover. This preliminary action prevents the finer first layer material from being sucked out during the vacuuming process while maintaining simple charging operations. The second layer acts as a barrier that seals the crucible opening, ensuring no material loss during vacuuming without complicating the charging procedure.
3Ease of manufacture
If the crucible is charged with silicon material of uniform particle size, then the charging process is more straightforward, but the single crystal diameter cannot be controlled effectively
Solution Approach 1:
The silicon material is segmented into three layers with progressively coarser particle sizes from bottom to top. This segmentation enables precise control over the melting and solidification process, allowing effective control of the single crystal diameter during growth. The graduated particle size distribution ensures proper material distribution and melting characteristics, resolving the contradiction between charging straightforwardness and diameter control precision.
Solution Approach 2:
The particle size parameter of the silicon material is systematically changed across different layers - from fine (0.1-1000 μm) in the first layer to medium (1-3 mm) in the second layer to coarse (10-70 mm) in the third layer. This parameter variation optimizes the charging and melting process, enabling effective control of single crystal diameter while maintaining a straightforward charging procedure through clear layer differentiation.
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 effectively prevents material loss during vacuuming, allows for efficient crucible charging, and enhances single crystal growth by optimizing the material process, increasing the likelihood of producing single crystals with a diameter greater than 1000 mm.
Implementation Method 1
disposing a second material layer on a side of the first material layer away from a bottom of the crucible, to cover the first material layer during vacuuming
Data Source
AI summary
A charging method of silicon material and a preparation method for single crystal are provided. The charging method includes: disposing the first material layer in the crucible; and disposing a second material layer on a side of the first material layer away from a bottom of the crucible, to cover the first material layer during vacuuming. The method for preparing a single crystal, using the silicon charging method described above. The preparation method for single crystal used the charging method for silicon material includes: covering a pot lid on the crucible to define a closed crucible body, and vacuuming the closed crucible body; lifting the closed crucible body into a single crystal furnace, and relieving pressure from the closed crucible body.