Silicon Ingot Oxygen Gradient for BMD Uniformity
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Solution Overview
Problem
The density of bulk microdefects (BMDs) in epitaxial silicon wafers decreases due to high-temperature processing, leading to insufficient gettering of heavy metal impurities and poor semiconductor device quality. Additionally, nitrogen doping to stabilize BMDs results in non-uniform BMD density along the ingot, failing to meet stringent customer requirements.
Innovation Solution
A method for growing single-crystal silicon ingots where the oxygen concentration is gradually decreased in the axial direction from the head to the tail portion by controlling the horizontal magnetic field's height or intensity during the crystal growth process, thereby maintaining uniform BMD density distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nitrogen doping treatment is adopted to obtain stable BMD cores, then BMD density increases, but BMD density becomes non-uniform along the axial direction of the ingot
Solution Approach 1:
The patent applies parameter changes by systematically varying oxygen concentration at different positions along the axial direction of the silicon ingot. By controlling oxygen concentration to decrease from head to tail portion, the patent achieves uniform BMD density distribution while maintaining BMD stability through nitrogen doping. This parameter optimization resolves the contradiction between achieving sufficient BMD density and maintaining uniform distribution.
2Quantity of substance
If oxygen concentration is increased to enhance BMD formation, then BMD density increases, but BMD density distribution becomes non-uniform
Solution Approach 1:
The patent implements local quality by establishing different oxygen concentration levels at different axial positions within the silicon ingot. The oxygen concentration is specifically controlled to be higher in the head portion and gradually decrease toward the tail portion, creating locally optimized conditions that result in uniform BMD density distribution throughout the entire ingot while maintaining sufficient overall BMD quantity.
3Stability of the object's composition
If high-temperature epitaxial growth is used to produce epitaxial silicon wafer, then crystalline integrity is improved, but BMD cores are eliminated resulting in insufficient BMD density
Solution Approach 1:
The patent applies preliminary action by pre-forming stable BMD cores through controlled nitrogen doping and optimized oxygen concentration distribution in the single-crystal silicon ingot before the epitaxial growth process. This ensures that when the high-temperature epitaxial growth occurs, the BMD cores are already established and protected, preventing their elimination and ensuring sufficient BMD density in the final epitaxial silicon wafer while maintaining crystalline integrity.
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 achieves a more uniform BMD density distribution along the single-crystal silicon ingot, effectively suppressing the increase of BMD density caused by nitrogen segregation, thus improving the quality and consistency of semiconductor devices.
Implementation Method 1
an initial height of a horizontal magnetic field is higher than a free surface of silicon melt; and during the body growing process of the single-crystal silicon ingot, an convection intensity of the silicon melt is controlled by adjusting a height or intensity of horizontal magnetic field
Implementation Method 2
an convection intensity of the silicon melt is controlled by adjusting a height or intensity of horizontal magnetic field
Data Source
AI summary
A method for growing a single-crystal silicon ingot and a single-crystal silicon ingot includes, during an initial stage of body growing process of the single-crystal silicon ingot, controlling an initial height of a horizontal magnetic field to be higher than a free surface of silicon melt. The method further includes, during the body growing process of the single-crystal silicon ingot, adjusting the horizontal magnetic field on convection intensity of the silicon melt to make oxygen concentration of the single-crystal silicon ingot to be decreased in an axial direction from a head portion to a tail portion.