Continuous Czochralski Silicon Ingot Growth via Magnetic Field Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The Continuous Czochralski method for growing single crystal silicon ingots faces challenges in maintaining consistent quality due to varying microdefect distributions, which are influenced by the ratio of crystal pull-rate to axial temperature gradient (v/G), leading to issues with agglomerated intrinsic point defects that affect the yield and quality of silicon wafers.
Innovation Solution
The method involves adding an initial charge of polycrystalline silicon to a crucible, maintaining a constant melt elevation level through continuous replenishment, and applying a magnetic field to control the melt flow and oxygen content, allowing for a constant pull rate and uniform defectivity control over a substantial portion of the ingot growth, thereby achieving 'perfect silicon' standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the crystal pull rate is increased to improve productivity, then the growth speed increases, but the microdefect distribution becomes non-uniform and quality deteriorates
Solution Approach 1:
The patent applies magnetic field parameters (strength and configuration) to change the physical state of the molten silicon, controlling convection patterns to achieve uniform microdefect distribution even at higher pull rates. The magnetic field strength is adjusted as a controllable parameter to optimize both productivity and quality
Solution Approach 2:
The patent implements monitoring and control systems that track microdefect formation and pull rate, using feedback loops to adjust process parameters in real-time. This ensures that quality standards are maintained while maximizing crystal growth speed
2Productivity
If polycrystalline silicon is continuously added to replenish the melt, then multiple ingots can be produced from a single crucible, but the added material adversely affects the properties of the growing ingot
Solution Approach 1:
The patent divides the melt into distinct zones using a magnetic field configuration that creates separate regions: one for crystal growth and another for polysilicon addition. This spatial segmentation allows continuous replenishment without contaminating the growing crystal
Solution Approach 2:
The magnetic field acts as an intermediary that controls the interaction between added polysilicon and the growing crystal. It directs the dissolution and integration of added material in a controlled manner, preventing adverse effects on crystal quality
3Shape
If the melt temperature is adjusted to control crystal diameter, then the desired diameter is achieved, but the microdefect distribution is affected
Solution Approach 1:
The patent uses magnetic field parameters as an additional control variable to decouple diameter control from temperature control. By adjusting magnetic field strength and configuration, the system can maintain optimal temperature for defect prevention while achieving desired crystal diameter through combined thermal and magnetic control
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 the growth of single crystal silicon ingots with significantly reduced agglomerated defects, meeting industry specifications for perfect silicon, with over 70% of the ingot length characterized by non-detectable FPDs, zero I-defects, and high GOI integrity, enhancing the yield and quality of silicon wafers.
Implementation Method 1
applying a magnetic field to control the melt flow
Implementation Method 2
applying a magnetic field to control the melt flow
Implementation Method 3
the temperature field in the vicinity of the melt/crystal interface drives the recombination of the point defects providing driving forces for their diffusion from the melt/crystal interface
Implementation Method 4
the temperature field in the vicinity of the melt/crystal interface drives the recombination of the point defects
Implementation Method 5
At a higher v/G, the convection of the point defects dominates their diffusion
Implementation Method 6
the ratio of the crystal pull-rate (v) to the magnitude of the axial temperature gradient in the vicinity of the interface (G)
Data Source
Figure 1A~1C
Figure 2
Figure 3
AI summary
A method for growing a single crystal silicon ingot by the continuous Czochralski method is disclosed. The melt depth and thermal conditions are constant during growth because the silicon melt is continuously replenished as it is consumed, and the crucible location is fixed. The critical v/G is determined by the hot zone configuration, and the continuous replenishment of silicon to the melt during growth enables growth of the ingot at a constant pull rate consistent with the critical v/G during growth of a substantial portion of the main body of the ingot.