Czochralski Silicon Crystal Growth Angle Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for producing silicon single crystals with a <100> orientation for semiconductor wafers used in power applications face challenges in reducing the frequency of dislocation formation, which necessitates stopping the crystal growth process.
Innovation Solution
A method involving the CZ method, where the initial cone is drawn with a crystal angle of 20° to 30°, active cooling, and controlled pulling speed, along with precise control of the crystal angle and temperature gradient to limit edge facet length and reduce dislocation formation, is employed. The single crystal is doped with phosphorus, arsenic, or antimony to achieve specific electrical resistance and diameter requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the drawing speed is increased to improve productivity, then the production efficiency increases, but dislocation formation frequency increases causing process termination
Solution Approach 1:
The patent applies parameter changes by optimizing the crystal angle to a specific range of 20° to 30° and controlling the drawing speed to not more than 75% of the limiting drawing speed. These parameter adjustments resolve the contradiction by finding an optimal operating point that maintains high productivity while suppressing dislocation formation through controlled growth conditions
Solution Approach 2:
The patent implements feedback control through active cooling systems and angle control mechanisms that monitor and adjust the crystal growth process in real-time. The angle control limits variations to not more than 0.01°/s, providing continuous feedback to maintain stable growth conditions and prevent dislocation formation even at high drawing speeds
2Reliability
If the crystal angle is increased to reduce edge facet length, then dislocation formation is reduced, but the initial cone shape and growth characteristics are affected
Solution Approach 1:
The patent resolves this contradiction by establishing an optimal crystal angle range of 20° to 30°, which is high enough to limit edge facet length and reduce dislocation formation, yet low enough to maintain acceptable initial cone shape and growth characteristics. This parameter optimization balances competing geometric requirements
Solution Approach 2:
The patent applies dynamics by implementing active angle control that limits crystal angle variations to not more than 0.01°/s. This dynamic control allows the system to maintain the optimal angle range throughout the growth process, adapting to changing conditions while preserving both the desired shape and low dislocation formation
3Reliability
If the drawing speed is reduced to reduce dislocation formation, then reliability improves, but productivity decreases
Solution Approach 1:
The patent resolves this contradiction by controlling the drawing speed to not more than 75% of the limiting drawing speed, which is the optimal parameter range that maintains high productivity while suppressing dislocation formation. This parameter optimization allows operating closer to the theoretical maximum speed without suffering from dislocation-related process terminations
4Reliability
If active cooling is applied to control temperature gradient, then edge facet length is limited and dislocation formation is reduced, but energy consumption increases
Solution Approach 1:
The patent applies local quality by implementing active cooling specifically in the region where edge facets form and dislocations originate. This localized cooling approach creates the necessary temperature gradient only where needed to control edge facet length and suppress dislocations, rather than cooling the entire system, thereby minimizing unnecessary energy consumption
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 significantly reduces dislocation frequency, allowing for larger diameter single crystals with controlled electrical resistance and edge facet length, enhancing the reliability of silicon single crystal growth for power semiconductor applications.
Implementation Method 1
The doping of a melt with n-type dopant; the single crystal accessible via the process is doped with phosphorus, arsenic, or antimony
Implementation Method 2
the drawing of an initial cone (1), a cylindrical section, and a final cone of the single crystal according to the CZ method
Implementation Method 3
the phase boundary between the growing single crystal and the melt
Implementation Method 4
the results of the investigation concluded that it is advantageous to establish a higher temperature gradient; the active cooling of the single crystal
Implementation Method 5
increase the convective transport of the melt
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a silicon single crystal with <100> orientation and a method for producing a silicon single crystal with <100> orientation. The single crystal is doped with a dopant of the n-type and comprises a starting cone, a cylindrical portion and an end cone, wherein a crystal angle in a center portion of the starting cone, the length of which equals not less than 50% of a length of the starting cone, is not less than 20° and not greater than 30°, and edge facets extend from an edge of the single crystal into the single crystal, wherein the edge facets in the starting cone and in the cylindrical portion of the single crystal each have a length not greater than 700 μm.