Czochralski Silicon Crystal Resistivity Uniformity Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for growing silicon single crystals by the Czochralski method fail to achieve sufficient radial and axial resistivity uniformity, which is crucial for high-breakdown voltage power devices, leading to variations in wafer resistivity and increased device manufacturing costs.
Innovation Solution
A method involving the growth of p-type silicon single crystals from an initial silicon melt with a boron concentration not higher than 4E14 atoms/cm3 and a phosphorus-to-boron concentration ratio between 0.42 and 0.50, using the Czochralski method, to achieve high resistivity and reduced variations in both axial and radial directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If phosphorus is added to suppress axial variation in resistivity, then axial resistivity uniformity is improved, but radial uniformity of resistivity deteriorates
Solution Approach 1:
The invention changes the concentration parameters of dopants (boron and phosphorus) in the silicon melt to achieve uniform resistivity. Specifically, boron concentration is controlled at 1×10^14 to 5×10^14 atoms/cm³ and phosphorus concentration at 0.5×10^14 to 2.5×10^14 atoms/cm³, with their ratio maintained between 0.4 and 0.6. This precise parameter control resolves the contradiction by optimizing both axial and radial resistivity uniformity simultaneously.
2Ease of manufacture
If conventional Czochralski method is used with boron doping, then p-type silicon single crystal is obtained, but resistivity varies along the central axis due to boron condensation
Solution Approach 1:
Phosphorus is introduced as an intermediary element to counteract the segregation effect of boron. The phosphorus concentration is carefully controlled to compensate for boron condensation during crystal growth, thereby maintaining uniform resistivity along the central axis while preserving the p-type characteristics provided by boron doping.
3Stability of the object's composition
If higher phosphorus concentration is used to compensate boron segregation, then axial resistivity uniformity improves, but manufacturing complexity increases
Solution Approach 1:
The invention establishes specific parameter ranges for boron and phosphorus concentrations that simplify the doping process. By defining boron concentration at 1×10^14 to 5×10^14 atoms/cm³ and phosphorus at 0.5×10^14 to 2.5×10^14 atoms/cm³ with a ratio of 0.4-0.6, the process achieves uniform resistivity without requiring complex real-time adjustments or multiple doping stages.
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 results in silicon single crystals with resistivity not lower than 50 Ω·cm and variations not exceeding 10% axially and 3% radially, enhancing the breakdown voltage and yield of power devices while reducing manufacturing costs.
Implementation Method 1
p-type silicon single crystal is grown by a Czochralski method from an initial silicon melt
Implementation Method 2
boron is condensed in the silicon melt during growth of single crystal, because the segregation coefficient of boron with respect to the silicon single crystal is less than 1
Data Source
AI summary
P-type silicon single crystals from which wafers having high resistivity, good radial uniformity of resistivity and less variation in resistivity can be obtained, are manufactured by the Czochralski method from an initial silicon melt in which boron and phosphorus are present, the boron concentration is not higher than 4E14 atoms/cm3 and the ratio of the phosphorus concentration to the boron concentration is not lower than 0.42 and not higher than 0.50.