Polycrystalline Silicon Rod Porosity Gradient
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The production of compact polycrystalline silicon rods is costly and inefficient, limiting their use in CZ crystal growing due to high energy consumption and process disruptions, while porous rods result in poor crystallization performance.
Innovation Solution
A polycrystalline silicon rod with a core and multiple regions of varying porosity, deposited using a controlled process with specific temperature and gas flow rates, allowing for a more economical and efficient production method that maintains high crystal pulling yields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compact polycrystalline silicon rods are produced using conventional deposition processes, then high purity silicon is achieved, but energy consumption increases and process disruptions occur
Solution Approach 1:
The patent applies local quality by creating distinct regions within the silicon rod with different porosity characteristics. The rod contains a compact central region (0-60% radius) with low porosity for structural integrity, surrounded by porous outer regions (60-100% radius) with higher porosity that reduce density and energy consumption. This spatial differentiation of material properties allows the rod to simultaneously achieve reliable crystal pulling from the compact core while reducing overall energy requirements through the lighter porous outer structure.
Solution Approach 2:
The patent employs composite materials by combining silicon regions with different porosity levels within a single rod structure. The composite consists of a dense compact silicon core integrated with porous silicon outer layers, creating a heterogeneous material system that leverages the advantages of both compact (high purity, structural stability) and porous (low density, reduced energy consumption) characteristics to resolve the contradiction between reliability and energy efficiency.
2Use of energy by moving object
If porous polycrystalline silicon rods are produced to reduce energy consumption, then production becomes more economical, but crystallization performance deteriorates
Solution Approach 1:
The patent resolves this contradiction by applying local quality through spatial differentiation of porosity. The compact central region (0-60% radius) provides the structural foundation and high-purity silicon necessary for reliable crystallization, while the porous outer regions (60-100% radius) contribute to reduced density and energy consumption. This localized assignment of functional properties ensures that the critical crystallization zone maintains compact structure while the outer regions provide energy efficiency benefits.
Solution Approach 2:
The patent uses segmentation by dividing the rod into distinct porosity zones: a compact inner core segment and porous outer shell segments. This segmentation allows each region to fulfill its specific function—the compact core ensures crystallization reliability while the porous segments reduce overall energy consumption—thereby resolving the contradiction between economical production and crystallization performance.
3Reliability
If uniform compact structure is maintained throughout the rod, then high purity is achieved, but production cost and energy consumption increase
Solution Approach 1:
The patent applies local quality by differentiating porosity across the rod radius rather than maintaining uniform compact structure throughout. The compact central region (0-60% radius) maintains high purity and structural integrity, while the porous outer regions (60-100% radius) reduce material density and production costs. This localized variation in structural quality allows cost reduction through porous material usage while preserving purity in the critical core region.
Solution Approach 2:
The patent employs composite materials by integrating compact high-purity silicon core with porous lower-cost outer layers. This composite structure maintains the essential purity requirements in the core region while utilizing more economical porous silicon in the outer regions, thereby reducing overall production cost while preserving the high purity necessary for semiconductor applications.
4Productivity
If deposition speed is increased to improve productivity, then more silicon is produced per unit time, but rod morphology becomes porous and fissured
Solution Approach 1:
The patent uses segmentation by dividing the deposition process into distinct stages that create different morphological zones. The early deposition stage creates a compact central region with controlled morphology, while subsequent faster deposition stages create porous outer regions. This temporal and spatial segmentation of the deposition process allows high productivity through accelerated outer layer deposition while preserving manufacturing precision in the critical core region.
Solution Approach 2:
The patent applies local quality by creating different morphological characteristics in different radial zones of the rod. The compact core region (0-60% radius) exhibits controlled morphology from slower deposition, while the outer regions (60-100% radius) exhibit porous structure from faster deposition. This local differentiation of morphological quality allows the system to achieve high overall productivity through fast outer deposition while maintaining precision where structurally critical.
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 produces rods with a compact core and porous regions, achieving high dislocation-free lengths and efficient crystal pulling performance, reducing energy consumption and process disruptions while maintaining economic viability.
Implementation Method 1
support bodies, usually thin filament rods (thin rods) made of silicon, are heated in a bell-shaped reactor ('Siemens reactor') by direct current passage
Implementation Method 2
a reaction gas containing hydrogen and one or more silicon-containing components is introduced. Trichlorosilane (SiHCl 3, TCS) or a mixture of trichlorosilane with dichlorosilane (SiH 2 Cl 2, DCS) and/or with tetrachlorosilane (SiCl 4, STC) is usually used as the silicon-containing component. High-purity polysilicon is deposited on the heated thin bars and the horizontal bridge
Data Source
AI summary
Polycrystalline silicon rod comprises a core (A) with a porosity of 0-0.01 around a thin rod, and at least two consecutive layers, which differ in their porosities by a factor of 1.7-23, where the outer layer (C) is less porous than the layer (B), and the polycrystalline silicon rod has an overall diameter of at least 150 mm. Independent claims are also included for: (1) manufacturing polysilicon fragments comprising crushing the above mentioned polycrystalline silicon rod; (2) the polycrystalline silicon fragments comprising fragments having different porosities and the fragments having a curved surface with a curvature radius of at least 75 mm, which are produced by the above mentioned method; and (3) producing the polycrystalline silicon rods, comprising introducing a reaction gas containing a silicon-containing component and depositing polycrystalline silicon on thin rods until a target rod diameter is achieved, which includes (a) depositing the core on thin rods in each case until a rod diameter of 15-60 mm is achieved, where the rod temperature is 1000-1150[deg] C, the concentration of the silicon-containing component in the reaction gas is 20-60 mole% and the supply of the silicon-containing component is 100-550 kg/hour per 1 m 2> of rod surface, (b) depositing a layer (B) with a porosity of 0.06-0.23 on the core starting with a rod diameter of at least 10% to a rod diameter of not > 90% of the target rod diameter, where the rod temperature is 1030-1130[deg] C, the concentration of the silicon-containing component in the reaction gas is 20-40 mole%, and the supply of the silicon-containing component is 80-200 kg/hour per 1 m 2> of the rod surface, and (c) depositing a layer (C) having a porosity of 0.01-0.1 on the layer (B), starting with a rod diameter of at least 50% up to a rod diameter of not > 100% of the target rod diameter, where the rod temperature is 960-1030[deg] C and is at least 20[deg] C lower than the rod temperature maintained during the step (b), the concentration of the silicon-containing component in the reaction gas is 15-35 mole% and the supply of the silicon-containing component is 10-130 kg/hour per 1 m 2> of the rod surface.