Monocrystal Growth H/R Ratio Control for Dislocation Inhibition
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Solution Overview
Problem
The existing methods for manufacturing monocrystals, such as those used for power MOS transistors, fail to adequately inhibit dislocation and maintain low resistivity, as the convection flow in the dopant-added melt leads to abnormal growth and dislocation issues.
Innovation Solution
Optimizing the amount of dopant-added melt in the crucible by controlling the distance from the lowermost portion to the top surface (H/R ratio) between 0.4 and 0.78, thereby stabilizing the melt temperature and reducing dislocation, while ensuring the resistivity at the upper end of the straight body remains at 1.0 mΩ·cm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the amount of dopant-added melt is increased, then the resistivity can be maintained at low levels, but the convection flow is strengthened causing abnormal growth and dislocation
Solution Approach 1:
The invention optimizes the H/R ratio parameter (distance from lowermost portion to top surface divided by top surface radius) to control convection flow intensity. By setting H/R within 0.4 to 0.78, the patent achieves stable temperature distribution that prevents abnormal growth and dislocation while maintaining low resistivity, resolving the contradiction between melt quantity and manufacturing precision
Solution Approach 2:
The patent applies preliminary control of the H/R ratio before crystal growth begins to prevent convection-induced abnormalities. By pre-establishing the optimal melt configuration, the invention prevents abnormal growth and dislocation from occurring in the first place, rather than correcting them after they appear
2Temperature
If the H/R ratio is increased, then the convection flow is strengthened which can deliver heat upward, but this causes temperature fluctuation and abnormal growth
Solution Approach 1:
The invention identifies and optimizes the H/R ratio as a critical parameter for temperature stability. By constraining H/R to the range of 0.4 to 0.78, the patent achieves stable temperature distribution in the melt that prevents abnormal growth, directly resolving the temperature stability issue
3Manufacturing precision
If the apex angle of the shoulder is adjusted to 40-60 degrees, then dislocation occurrence can be inhibited, but this alone is insufficient to prevent abnormal growth in dopant-added melts
Solution Approach 1:
The invention combines multiple control parameters (H/R ratio and shoulder apex angle) into a unified approach. By merging the optimization of H/R ratio with the established shoulder angle requirements, the patent achieves comprehensive dislocation inhibition and abnormal growth prevention that neither parameter alone can accomplish
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 effectively inhibits dislocation and maintains low resistivity in the monocrystal, allowing for the production of high-quality silicon wafers with reduced abnormal growth and improved manufacturing efficiency.
Implementation Method 1
a convection flow seems to be occurring in a dopant-added melt received in a crucible by a temperature difference between a part of the melt positioned at a lowermost portion of the crucible and a top surface of the melt
Implementation Method 2
convection flow seems to be occurring in a dopant-added melt received in a crucible by a temperature difference between a part of the melt positioned at a lowermost portion of the crucible and a top surface of the melt
Data Source
AI summary
A manufacturing method of a monocrystal includes: a shoulder-formation step to form a shoulder of the monocrystal; and a straight-body-formation step to form a straight body of the monocrystal, in which, in the shoulder-formation step, providing that a distance from a lowermost portion inside the crucible to a top surface of the dopant-added melt is defined as H (mm) and a radius of the top surface of the dopant-added melt is defined as R (mm), the shoulder starts to be formed in a condition that a relationship of 0.4<H/R<0.78 is satisfied.