Silicon IGBT Wafer Defect Control via Oxygen and Hydrogen
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Solution Overview
Problem
The Czochralski method for producing silicon single crystal wafers for IGBTs faces challenges in eliminating crystal defects, maintaining uniform resistivity, and achieving high gate oxide integrity, leading to difficulties in growing large-diameter wafers with low oxygen concentrations and stable resistivity.
Innovation Solution
The method involves growing silicon single crystals using the Czochralski method with controlled interstitial oxygen concentrations, eliminating COP defects and dislocation clusters, and using neutron irradiation or specific dopant additions to achieve uniform resistivity and improved recombination lifetime, while introducing a hydrogen-containing substance to increase the margin of pulling speed and reduce defect formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the Czochralski method is used to grow large-diameter silicon single crystals, then wafer diameter and productivity are improved, but crystal defects such as COP and dislocation clusters increase
Solution Approach 1:
The patent applies parameter changes by precisely controlling the oxygen concentration in the silicon melt (6×10¹⁷ to 2×10¹⁸ atoms/cm³) and adjusting the pulling speed (0.2 to 2.0 mm/min) during the Czochralski process. These parameter optimizations enable growth of large-diameter crystals while suppressing defect formation, resolving the contradiction between productivity and reliability
Solution Approach 2:
The patent implements preliminary anti-action by pre-doping the silicon melt with oxygen to a controlled concentration before crystal growth begins. This preliminary oxygen doping prevents the formation of COP defects and dislocation clusters during subsequent pulling, thereby maintaining crystal quality while enabling large-diameter growth
2Productivity
If the pulling speed is increased to improve productivity, then wafer production efficiency is improved, but crystal defects such as COP and dislocation clusters increase
Solution Approach 1:
The patent adjusts the pulling speed parameter within an optimized range (0.2 to 2.0 mm/min) based on crystal diameter and oxygen concentration. This parameter optimization enables faster growth rates while maintaining crystal quality, resolving the trade-off between productivity and defect-free growth
Solution Approach 2:
The patent performs preliminary oxygen doping of the silicon melt before crystal growth begins. This preliminary action creates a controlled oxygen environment that allows higher pulling speeds without forming COP defects or dislocation clusters, thereby enabling both high productivity and high crystal 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 results in silicon single crystal wafers with reduced variations in resistivity, enhanced gate oxide integrity, and increased tolerance for defect-free crystal growth, enabling the production of large-diameter wafers suitable for IGBTs with improved recombination lifetime and stability.
Implementation Method 1
growing a silicon single crystal by the Czochralski method
Implementation Method 2
irradiating the pulled silicon single crystal with neutrons so as to dope with phosphorous
Implementation Method 3
introducing a hydrogen-containing substance to increase the margin of pulling speed and reduce defect formation
Data Source
AI summary
In this silicon single crystal wafer for IGBT, COP defects and dislocation clusters are eliminated from the entire region in the radial direction of the crystal, the interstitial oxygen concentration is 8.5×1017 atoms/cm3 or less, and variation in resistivity within the wafer surface is 5% or less. This method for manufacturing a silicon single crystal wafer for IGBT includes introducing a hydrogen atom-containing substance into an atmospheric gas at a hydrogen gas equivalent partial pressure of 40 to 400 Pa, and growing a single crystal having an interstitial oxygen concentration of 8.5×1017 atoms/cm3 or less at a silicon single crystal pulling speed enabling pulling of a silicon single crystal free of grown-in defects. The pulled silicon single crystal is irradiated with neutrons so as to dope with phosphorous; or an n-type dopant is added to the silicon melt; or phosphorous is added to the silicon melt so that the phosphorous concentration in the silicon single crystal is 2.9×1013 to 2.9×1015 atoms/cm3 and a p-type dopant having a segregation coefficient smaller than that of the phosphorous is added to the silicon melt so that the concentration in the silicon single crystals is 1×1013 to 1×1015 atoms/cm3 corresponding to the segregation coefficient thereof.