Polysilicon Rod Morphology Control via Resistance Index
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Solution Overview
Problem
The existing methods for producing polycrystalline silicon struggle to control the morphology of polysilicon rods during deposition, leading to inefficient processing and economically unacceptable yields, especially in the CZ process, due to the difficulty in determining and controlling the morphology in real-time.
Innovation Solution
A method that calculates a morphology index M based on resistance values during deposition, allowing for real-time control of the deposition process to achieve desired morphology values between 0.8 and 2.5, thereby ensuring precise production of polysilicon with varying compactness and porosity suitable for different applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If real-time monitoring and control of morphology during deposition is implemented, then manufacturing precision and productivity are improved, but device complexity and measurement difficulty increase
Solution Approach 1:
The invention monitors morphology by measuring electrical resistance, a physical parameter that changes with morphology during deposition. By tracking resistance changes in real-time, the system can detect morphology variations and adjust deposition parameters accordingly, achieving precise morphology control without complex imaging or measurement systems
Solution Approach 2:
The invention replaces complex mechanical or optical measurement systems with an electrical resistance measurement approach. Instead of using sophisticated morphological analysis equipment, the system uses simple electrical resistance measurements to infer morphology, significantly simplifying the control system while maintaining measurement effectiveness
2Manufacturing precision
If deposition time is extended to produce compact polysilicon, then manufacturing precision is improved, but productivity deteriorates
Solution Approach 1:
The invention implements real-time feedback control by continuously monitoring electrical resistance during deposition. When the resistance indicates that the desired morphology is approaching or has been achieved, the system can automatically terminate the deposition process or adjust parameters, preventing both over-deposition and unnecessary extended deposition times, thus optimizing the balance between morphology quality and productivity
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 enables efficient production of polysilicon with controlled morphology, optimizing productivity and quality assurance by allowing for continuous monitoring and adjustment of the deposition process, resulting in polysilicon suitable for semiconductors and solar applications.
Implementation Method 1
heating support bodies (usually composed of polysilicon) in a bell-shaped reactor (Siemens reactor) by way of the direct passage of current
Implementation Method 2
a first resistance value R1 of the silicon rod is determined
Implementation Method 3
The silicon-containing component is generally monosilane (SiH4) or a halosilane of the general composition SiHnX4-n (n=0, 1, 2, 3; X=Cl, Br, I). It is typically a chlorosilane or a chlorosilane mixture, usually trichlorosilane (SiHCl3, TCS). Predominantly, SiH4 or TCS is used in a mixture with hydrogen. The structure of a typical Siemens reactor is described by way of example in EP 2 077 252 A2 or EP 2 444 373 A1.
Implementation Method 4
At these temperatures, the silicon-containing component of the reaction gas decomposes and elemental silicon is deposited from the vapour phase as polysilicon
Data Source
AI summary
Method for producing polycrystalline silicon by inducing reaction gas, which in addition to hydrogen contains silane and/or at least one halosilane, into a reaction space of a vapour deposition reactor. The reaction space comprises at least one filament rod heated by the passage of current and on which by means of deposition silicon is deposited to form a polycrystalline silicon rod. A determination of morphology of the silicon rod during deposition at a rod temperature a first resistance R1 of the silicon rod is determined byR1=UIwhere U is a voltage between two ends of the silicon rod and I is a current strength, and a second resistance R2 is determined byR2=ρLAwere ρ is a resistivity of silicon, L is a length of the silicon rod and A is a cross-sectional area of the silicon rod. A morphology index M is calculated from the ratio R1/R2.