Monocrystalline Silicon Emissivity-Based Resistivity Control
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Solution Overview
Problem
The existing methods for producing monocrystalline silicon by the Czochralski method face challenges in reducing Light Point Defects (LPD) on silicon wafers due to decreased emissivity of the inner wall surface of the top chamber, leading to increased Crystal Originated Particles (COP) and vacancies, which are not effectively addressed by current cleaning processes or adjustments in heat shield distances.
Innovation Solution
A production method that measures the emissivity of the inner wall surface of the top chamber and adjusts the target resistivity of the monocrystalline silicon based on the measured emissivity, with specific thresholds for arsenic, phosphorus, and antimony dopants, to produce silicon wafers with reduced LPD by determining the appropriate resistivity range to prevent COP generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the emissivity of the inner wall surface of the top chamber is high, then heat radiation to the monocrystalline silicon is sufficient for stable growth, but evaporant adhesion reduces the emissivity over time, leading to decreased heat radiation efficiency and increased COP defects
Solution Approach 1:
The patent applies preliminary action by pre-heating the monocrystalline silicon to a high temperature (1400°C to 1600°C) before pulling. This preliminary heating ensures that even when emissivity decreases and heat radiation reduces, the silicon maintains sufficient temperature for stable growth, preventing COP defects while accounting for the emissivity degradation over time
Solution Approach 2:
The patent changes the temperature parameter by setting a specifically high pre-heating temperature range (1400°C to 1600°C) that compensates for reduced heat radiation from the chamber wall. This parameter adjustment ensures the temperature gradient at the solid/liquid interface remains within the optimal range (1.0 to 3.0°C/mm) despite emissivity changes
2Reliability
If the monocrystalline silicon is pre-heated to a high temperature before pulling, then the temperature gradient can be maintained despite decreased emissivity, but energy consumption increases
Solution Approach 1:
The patent applies partial or excessive action by pre-heating the silicon to a temperature (1400°C to 1600°C) that exceeds the typical pulling temperature. This excessive pre-heating ensures the temperature gradient remains stable throughout the pulling process even when emissivity decreases, avoiding the need for continuous high energy input during pulling
3Reliability
If cleaning processes are performed to remove evaporant deposits, then emissivity can be restored, but production time and operational complexity increase
Solution Approach 1:
The patent applies preliminary action by performing pre-heating before the pulling process begins. This preliminary action compensates for the effects of evaporant deposition without requiring intermediate cleaning steps during production, thereby maintaining emissivity effects without interrupting the production cycle
Solution Approach 2:
The patent maintains continuity of useful action by enabling uninterrupted pulling operations. The pre-heating compensation method allows the production process to continue without stopping for cleaning, even as emissivity gradually decreases, thus maintaining high productivity while ensuring product quality
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 reduces LPD on silicon wafers by controlling the resistivity of monocrystalline silicon in response to varying emissivity levels, minimizing the generation of COP and associated defects, thereby improving the quality of silicon wafers.
Implementation Method 1
The emissivity ε is an index showing efficiency for a surface of an object to emit a thermal energy... The radiation herein is an infrared radiation whose wavelength ranges from 0.77 μm to 1,000 μm
Implementation Method 2
oxygen (O2), which is eluted from the quartz crucible primarily made of silicon dioxide (SiO2), reacts with the silicon melt to generate silicon oxide(s) (SixOy) (0xOy) evaporates from a surface of the silicon melt
Data Source
AI summary
A production method of monocrystalline silicon includes: measuring an emissivity of an inner wall surface of a top chamber; and determining a target resistivity of monocrystalline silicon based on the emissivity measured in the measuring, thereby producing the monocrystalline silicon. In determining the target emissivity on a crystal center axis at a position for starting formation of a straight body of the monocrystalline silicon in the producing, when the emissivity is 0.4 or less, the target resistivity is determined to be less than a resistivity value of 3.0 mΩ·cm when the dopant is arsenic.