Polycrystalline Silicon Rod Manufacturing with Off-Angle Core Wire
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Solution Overview
Problem
Conventional methods for manufacturing polycrystalline silicon rods face limitations in achieving high purity due to impurity contamination and strain-related breakage, which affects the quality and productivity of single-crystalline silicon ingots, especially when using polycrystalline silicon chunks as raw material.
Innovation Solution
A method involving the use of a silicon core wire cut from a single-crystalline silicon ingot grown by the Czochralski or floating zone method, with a specific off-angle and oxygen concentration, to reduce impurity contamination and enhance strength, thereby improving the purity and single-crystallization efficiency of the polycrystalline silicon rod produced by CVD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heat treatment at high temperature is performed to remove internal strain from polycrystalline silicon rod, then breakage during cutting is prevented, but impurity contamination from furnace materials and environment increases
Solution Approach 1:
The patent introduces a specially designed susceptor as an intermediary component that serves dual functions: it provides mechanical support to prevent rod breakage during heat treatment, and its specific material composition and structure minimize impurity contamination from the furnace environment. The susceptor acts as a barrier between the polycrystalline silicon rod and the furnace atmosphere.
Solution Approach 2:
The patent optimizes the heat treatment parameters including temperature range, heating rate, and atmosphere composition to achieve strain removal while minimizing impurity uptake. By carefully controlling these parameters, the process removes internal strain without excessive impurity contamination from furnace materials.
2Volume of moving object
If polycrystalline silicon chunks are recharged during crystal pulling to produce large diameter silicon ingots, then ingot diameter is increased, but impurity concentration in silicon melt increases reducing single-crystalline silicon purity
Solution Approach 1:
The patent performs preliminary purification of polycrystalline silicon chunks before they are charged into the silicon melt. This pre-purification step removes impurities that would otherwise be introduced during recharging operations, allowing multiple charges to be performed while maintaining high purity of the final single-crystalline silicon ingot.
3Loss of time
If polycrystalline silicon rod is cut immediately after CVD growth to obtain core wire, then processing time is reduced, but rod breakage occurs due to internal strain
Solution Approach 1:
The patent performs preliminary strain removal heat treatment on the polycrystalline silicon rod immediately after CVD growth, before cutting operations. This preliminary action eliminates internal strains that would cause breakage during subsequent cutting, enabling the rod to be cut into core wires without breakage while maintaining efficient processing.
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 results in a polycrystalline silicon rod with low impurity contamination and high single-crystallization efficiency, reducing breakage during the CVD process and improving the one-pass rate in the floating zone method, while maintaining high purity and strength.
Implementation Method 1
polycrystalline silicon is deposited on the surface of the silicon core wire
Implementation Method 2
a single-crystalline silicon ingot which is grown by a Czochralski method
Implementation Method 3
a single-crystalline silicon ingot grown by the Czochralski or floating zone method
Data Source
AI summary
The present invention is a method of manufacturing polycrystalline silicon rods, wherein silicon is deposited onto a silicon core wire by a chemical vapor deposition (CVD) method such that a silicon member, which is cut out from a single-crystalline silicon ingot at an off-angle range of 5 to 40 degrees relative to a crystal habit line of the ingot, is used as the silicon core wire. The single-crystalline silicon ingot is preferably grown by a Czochralski (CZ) method or floating zone (FZ) method, such that the ingot preferably has an interstitial oxygen concentration of 7 ppma to 20 ppma. Silicon rods produced by this method are less likely to suffer a breakage caused by cleavage during the growth process of polycrystalline silicon during CVD, and exhibit improved FZ method success rates. The polycrystalline silicon rods produced by this method also have low impurity contamination and high single-crystallization efficiency.