Czochralski Silicon Crystal Growth Oxygen Control
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Solution Overview
Problem
Conventional methods for controlling oxygen concentration during the Czochralski process for growing large-diameter silicon single crystals fail to maintain stability due to unsteady melt flow and oxygen behavior, leading to high oxygen concentrations and crystal defects, especially for crystals exceeding 200 mm in diameter.
Innovation Solution
A silicon single crystal growth method using a Czochralski process with a strong horizontal magnetic field, where the crucible is rotated at a rate between 0.6 rpm and 1.5 rpm, with a magnetic field intensity of 0.2T or more, and the rate is adjusted to minimize oxygen concentration variation along the crystal growth length, maintaining a stable process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a strong horizontal magnetic field is applied to control oxygen concentration during Czochralski process, then oxygen concentration can be controlled for small-diameter crystals (≤200mm), but oxygen concentration control deteriorates for large-diameter crystals (≥300mm) due to unsteady melt flow
Solution Approach 1:
The patent applies a dynamic crucible rotation rate strategy that changes during the crystal growth process. The rotation rate is set higher (0.5-2.0 rpm) at the initial stage when melt volume is smaller, then reduced (0.1-0.5 rpm) at the final stage when melt volume increases. This dynamic adjustment compensates for the changing melt flow characteristics, maintaining stable oxygen concentration control throughout the entire growth process for large-diameter crystals.
Solution Approach 2:
The patent changes the operational parameters (crucible rotation rate and pulling speed) based on the growth stage and crystal diameter. By adjusting these parameters dynamically, the system adapts to the changing melt volume and flow patterns, resolving the contradiction between maintaining oxygen concentration control and dealing with unsteady melt flow in large-diameter crystal growth.
2Manufacturing precision
If crucible rotation rate is increased to control oxygen concentration, then oxygen concentration can be reduced, but crystal defect level increases and manufacturing precision deteriorates
Solution Approach 1:
The patent uses dynamic adjustment of crucible rotation rate, applying higher rotation speeds (0.5-2.0 rpm) only at the initial growth stage when oxygen concentration needs active control, then reducing to lower speeds (0.1-0.5 rpm) at the final stage. This temporal differentiation allows oxygen concentration control when needed while avoiding excessive rotation that would generate crystal defects during later growth phases.
Solution Approach 2:
The patent implements periodic or stage-based changes in crucible rotation rate and pulling speed. By applying different rotation rates at different growth stages, the system achieves oxygen concentration control during critical early phases while maintaining crystal quality during later phases, thus resolving the contradiction between oxygen control and defect prevention.
3Manufacturing precision
If argon gas inflow amount or pressure is increased to control oxygen concentration, then oxygen concentration can be adjusted, but process complexity and energy consumption increase
Solution Approach 1:
The patent replaces complex gas flow control mechanisms with a simpler mechanical approach using crucible rotation and pulling speed control. By utilizing the magnetic field's natural effect on melt flow combined with mechanical rotation control, the system achieves oxygen concentration control without requiring complex gas inflow regulation systems, thereby reducing process complexity and 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 method effectively reduces oxygen concentration deviation and stabilizes the pulling speed, enabling the growth of high-quality silicon single crystals with reduced crystal defects and improved process stability for diameters up to 300 mm or more, suitable for advanced semiconductor devices like NAND flash.
Implementation Method 1
using a Czochralski process by dipping a seed into a silicon melt received in a quartz crucible and pulling up the seed while rotating the quartz crucible and applying a strong horizontal magnetic field
Implementation Method 2
as volume of a melt is larger, flow of the melt is unsteadier, and consequently oxygen behavior becomes complicated
Implementation Method 3
the quartz crucible reacts with the silicon melt and is dissolved in the melt. Consequently, oxygen is eluted from the crucible and inflowed into a single crystal through a solid-liquid interface
Implementation Method 4
a quartz crucible is required to receive a silicon melt melted by a heater
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The present invention relates to a semiconductor single crystal growth method, which uses a Czochralski process for growing a semiconductor single crystal (1) through a solid-liquid interface by dipping a seed into a semiconductor melt received in a quartz crucible (10) and pulling up the seed while rotating the quartz crucible (10) and applying a strong horizontal magnetic field, wherein the seed is pulled up while the quartz crucible (10) is rotated with a rate between 0.6 rpm and 1.5 rpm.