Silicon Single Crystal Carbon Doping via Crushed Polysilicon Rod Ends
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Solution Overview
Problem
Existing methods for producing silicon single crystals using the Czochralski method face challenges in incorporating carbon uniformly and efficiently, leading to dislocations and reduced strength, while also increasing production costs and contamination risks.
Innovation Solution
The process involves using crushed polycrystalline silicon rods produced by the Siemens process, where the rod ends containing a high carbon concentration are crushed and used as silicon raw material, allowing for precise carbon incorporation and improved flowability, thereby enhancing the strength and reducing dislocations in silicon single crystals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If carbon powder or solid carbon is used for doping silicon single crystals, then carbon can be incorporated into the crystal, but carbon does not mix or dissolve properly causing dislocations and the method cannot achieve precise doping concentration
Solution Approach 1:
The invention changes the physical state of carbon from solid (carbon powder or solid carbon pieces) to gaseous form (carbon-containing gas such as methane, carbon monoxide, or carbon dioxide). This parameter change enables uniform dissolution and mixing of carbon in the silicon melt, achieving precise doping concentrations without the aggregation and floating problems associated with solid carbon doping methods.
2Quantity of substance
If high concentration carbon is used at the initial stage of silicon dissolution, then carbon doping is achieved, but the quartz crucible reacts with carbon shortening its durability
Solution Approach 1:
The invention applies preliminary action by introducing carbon-containing gas before or during the initial stage of silicon dissolution, but controls the carbon concentration to prevent excessive reaction with the quartz crucible. The gas phase carbon provides a controllable, gradual doping process that avoids the harsh conditions caused by solid carbon, thereby protecting crucible durability while achieving the desired carbon incorporation.
3Quantity of substance
If polycrystalline silicon with high carbon concentration (3 ppma or higher) is used, then carbon doping is achieved, but production cost increases and metal contamination risk arises
Solution Approach 1:
The invention uses carbon-containing gas (such as methane, carbon monoxide, or carbon dioxide) as a substitute for expensive polycrystalline silicon with high carbon concentration. The gas phase carbon source provides the necessary carbon doping effect without requiring the costly and complex production processes needed to create and handle high-carbon polycrystalline silicon materials, thereby significantly reducing production costs.
Solution Approach 2:
The invention employs inexpensive carbon-containing gases (methane, carbon monoxide, carbon dioxide) as disposable doping agents. These gases can be easily introduced and controlled during the crystal growth process, and any excess is simply vented without requiring expensive material recovery or handling procedures, making the process economically viable compared to using precious high-carbon polycrystalline silicon.
4Strength
If oxygen is incorporated from quartz crucible or impurities such as carbon and nitrogen are doped to prevent dislocation, then strength of silicon single crystals is enhanced, but electric properties are impaired
Solution Approach 1:
The invention precisely controls the carbon concentration parameter through gas phase doping, achieving optimal strength enhancement without excessive carbon content that would harm electric properties. By using gas phase carbon sources, the carbon is uniformly distributed at controlled concentrations (typically 0.1-10 ppma), providing sufficient strength improvement while maintaining the electrical characteristics needed for semiconductor applications.
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 method enables the production of silicon single crystals with controlled carbon concentration, suppressing dislocations and improving strength, while maintaining low production costs and minimizing metal contamination, and is suitable for both semiconductor and solar cell substrates.
Implementation Method 1
heating a silicon raw material held in a crucible to provide a silicon melt
Implementation Method 2
allowing carbon to be mixed and dissolved, which enables the carbon to be incorporated with low cost and which provides excellence in operability
Data Source
AI summary
In a process for producing a silicon single crystal in which carbon is incorporated in order to inhibit crystal defects, provided is a process which easily allows carbon to be mixed and dissolved into a silicon melt. The process for producing a silicon single crystal, which involves allowing a silicon single crystal to grow during its pulling-up from the silicon melt held in a crucible, uses as at least part of a silicon raw material, crushed materials of a polycrystalline silicon rod produced by Siemens process that are obtained by crushing an end of the rod in the vicinity contacting a carbon core wire holding member.