Silicon Monocrystal Resistivity Control via Gas Doping
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Solution Overview
Problem
Existing methods for manufacturing silicon monocrystals using the CZ method result in non-uniform resistivity distribution along the crystal length, making it difficult to achieve high-quality monocrystals with uniform resistivity, especially for large-diameter crystals, which increases manufacturing costs.
Innovation Solution
A method involving the FZ method that uses P-type or N-type silicon crystals pulled up by the CZ method, where impurities are supplied through a gas doping process, with the doping-gas flow rate calculated based on the resistivity distribution of the raw material and target resistivity of the product-monocrystal, ensuring uniform resistivity distribution along the crystal length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a silicon-polycrystal material having a large diameter (140 mm or more) is used for manufacturing a grown crystal, then the diameter of the grown crystal can be increased, but the manufacturing cost is increased because the price of the raw material is set high due to yield problems
Solution Approach 1:
The invention changes the resistivity parameter of the raw material from high resistivity (1000 Ω·cm) to low resistivity (0.1 Ω·cm) by using CZ method silicon ingots as starting material. This parameter change allows the use of cost-effective raw materials while achieving the desired electrical properties through controlled gas doping during the FZ growth process
Solution Approach 2:
The invention introduces gas doping as an intermediary mechanism to transfer impurities from the atmosphere into the molten silicon during FZ growth. This intermediary process enables precise control of resistivity in the grown crystal, allowing the use of low-cost raw materials to be transformed into high-quality monocrystals with uniform resistivity distribution
2Ease of manufacture
If a P-type or N-type silicon crystal having been pulled up by CZ method is used as the raw material for forming a crystal by FZ method, then the manufacturing cost can be reduced, but the resistivity distribution along the longitudinal direction of the crystal becomes non-uniform
Solution Approach 1:
The invention implements a feedback control mechanism where the resistivity distribution of the final crystal is measured and used to adjust the gas doping parameters in subsequent FZ growth processes. By establishing the relationship between gas flow rate and impurity incorporation, the system can compensate for the non-uniform impurity distribution inherited from the CZ raw material, achieving uniform resistivity in the grown crystal
Solution Approach 2:
The invention performs preliminary characterization of the CZ raw material's resistivity distribution before FZ growth, and uses this information to pre-calculate the optimal gas doping profile. This preliminary action allows the FZ process to compensate in advance for the non-uniform impurity distribution in the raw material, ensuring uniform resistivity in the final crystal
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 allows for the production of silicon monocrystals with uniform resistivity distribution, reducing manufacturing costs by optimizing the doping-gas flow rate and ensuring consistent quality, even for large-diameter crystals.
Implementation Method 1
supplying impurities whose conductivity type is the same as that of the raw material by a gas doping method
Implementation Method 2
recrystallizing the raw material by the FZ method
Implementation Method 3
recrystallizing the raw material by the FZ method for obtaining a product monocrystal
Data Source
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AI summary
According to a method of manufacturing a silicon monocrystal by FZ method, a P-type or N-type silicon crystal having been pulled up by CZ method is used as a raw material (6). While impurities whose conductivity type is the same as that of the raw material (6) are supplied by a gas doping method, the raw material (6) is recrystallized by an induction-heating coil (3) for obtaining a product-monocrystal (8).