Nitrogen-Doped Silicon Ingot Pulling Speed Control
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Solution Overview
Problem
Conventional methods for producing nitrogen-doped single crystal silicon ingots result in uneven Bulk Micro Defect (BMD) content and density, leading to a low proportion of silicon wafers with highly clean surfaces due to the alternating distribution of defect areas, such as pure vacancy and interstitial areas, which affects the quality of semiconductor integrated circuits.
Innovation Solution
A method is developed to produce nitrogen-doped single crystal silicon ingots by adjusting the pulling speed based on the distribution of defect areas, specifically targeting the pure vacancy area to achieve a higher proportion of silicon wafers with clean surfaces, by evaluating the distribution of defect areas in sample wafers and determining the appropriate pulling speed for each area during the ingot production process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional Czochralski method is used to produce nitrogen-doped single crystal silicon ingot, then silicon melt can be melted and monocrystalline silicon ingot can be grown, but the BMD content and density are unevenly distributed resulting in low proportion of silicon wafers with highly clean surfaces
Solution Approach 1:
The patent applies dynamics by making the pulling speed adjustable and variable during the crystal growth process. Instead of maintaining a constant pulling speed, the method dynamically changes the pulling speed based on the radial position and depth in the silicon ingot to control BMD distribution. This enables the system to adapt to different growth stages and achieve uniform BMD distribution throughout the ingot, resolving the contradiction between manufacturing precision and productivity.
Solution Approach 2:
The patent changes the pulling speed parameter during the crystal growth process to control defect distribution. By adjusting the pulling speed according to specific radial positions and depths, the method optimizes BMD formation and distribution. This parameter change strategy enables uniform BMD distribution while maximizing the proportion of high-quality silicon wafers, simultaneously improving both manufacturing precision and productivity.
2Stability of the object's composition
If constant pulling speed is maintained during crystal growth, then the production process is simple and stable, but defect areas such as pure vacancy and interstitial areas alternate distribution reducing wafer quality
Solution Approach 1:
The patent transforms the static constant pulling speed into a dynamic variable pulling speed that changes based on radial position and depth. This dynamic adjustment maintains process stability while achieving uniform defect distribution. The pulling speed is modified in response to specific growth conditions, allowing the system to maintain stability throughout the process while improving manufacturing precision through controlled variations.
Solution Approach 2:
The patent applies local quality by implementing different pulling speeds for different radial positions and depths in the silicon ingot. Instead of a uniform approach, the method tailors the pulling speed to local conditions, creating optimal BMD distribution in each region. This localized control strategy ensures uniform defect distribution throughout the entire ingot while maintaining overall process stability.
3Reliability
If nitrogen doping is applied to single crystal silicon, then metal impurities can be absorbed and gate oxide film integrity can be improved, but alternating defect areas are formed reducing the proportion of clean surface wafers
Solution Approach 1:
The patent uses dynamic pulling speed adjustment to control the distribution of nitrogen-doped regions and resulting BMDs. By varying the pulling speed during growth, the method ensures uniform BMD distribution throughout the ingot, which in turn provides uniform metal impurity absorption capability. This maintains gate oxide film integrity across all wafers while eliminating alternating defect areas, thus improving both reliability and manufacturing precision.
Solution Approach 2:
The patent changes the pulling speed parameter to optimize nitrogen distribution and BMD formation. By adjusting the pulling speed according to radial position and depth, the method achieves uniform nitrogen doping效果 and BMD distribution. This parameter optimization ensures that all wafers benefit from nitrogen's impurity absorption capability while maintaining uniform surface cleanliness, improving both reliability and manufacturing precision.
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 allows for the production of nitrogen-doped single crystal silicon ingots with only the pure vacancy area, increasing the proportion of silicon wafers with highly clean surfaces, thereby improving the quality and reducing waste, as the BMDs are uniformly distributed and effectively absorb metal impurities, enhancing the integrity of the gate oxide film and reducing leakage current.
Implementation Method 1
The Czochralski method includes melting polysilicon in a quartz crucible to acquire a silicon melt
Implementation Method 2
a monocrystalline silicon ingot is grown at the phases-interface during pulling
Data Source
AI summary
A method for producing a nitrogen-doped single crystal silicon ingot includes, after cutting a reference ingot into sample silicon wafers, selecting a plurality of silicon wafers to be tested and evaluating a distribution of defect areas in the plurality of silicon wafers, wherein the defect areas comprise any of a pure vacancy area, a pure interstitial area, and an alternating distribution area of a pure vacancy area and a pure interstitial area. The method also includes determining a distribution position of each defect area in the reference ingot based on the distribution of the defect areas in the plurality of silicon. Then, in a production process of the nitrogen-doped single crystal silicon ingot, a pulling is performed at a set target pulling speed corresponding to each defect area which refers to the distribution position of each defect area in the reference nitrogen-doped single crystal silicon ingot.