Silicon Wafer Thermal Processing Defect Reduction
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Solution Overview
Problem
Existing silicon wafer manufacturing methods face challenges in reducing grown-in defects and preventing slip during rapid heating/cooling thermal processes, while also improving surface roughness, due to long heat treatment times and the need for additional processing steps like nitride film removal.
Innovation Solution
A manufacturing method involving a Czochralski process for producing silicon wafers, with a first heat treatment using a gas mixture of 0.01-1.00 vol% oxygen and a rare gas for rapid heating to 1300°C, followed by a second heat treatment with 20-100 vol% oxygen for rapid cooling, to form a Denuded Zone layer that reduces defects and improves surface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If long heat treatment time is used to reduce grown-in defects, then defect reduction is improved, but productivity deteriorates
Solution Approach 1:
The patent changes the temperature parameter from conventional 1000-1350°C to a higher range of 1400-1600°C, and changes the time parameter from 50 hours or less to a much shorter duration. This parameter transformation enables rapid defect reduction while maintaining high productivity, resolving the contradiction between reliability and productivity.
Solution Approach 2:
The patent applies rapid thermal processing that skips the long annealing time required by conventional methods. By rapidly heating to 1400-1600°C and maintaining this temperature for a short period, the process rushes through the defect reduction mechanism without requiring extended treatment time, thus improving productivity while achieving defect reduction.
2Reliability
If heat treatment is performed in nitrogen atmosphere to reduce defects, then defect reduction is improved, but manufacturing complexity increases due to nitride film formation requiring additional removal steps
Solution Approach 1:
The patent uses an inert gas atmosphere (such as argon or nitrogen) during the rapid thermal processing. This inert environment prevents unwanted chemical reactions at the silicon surface, avoiding nitride film formation that would require additional removal steps, thereby simplifying the manufacturing process while still achieving defect reduction through the thermal treatment.
Solution Approach 2:
The patent extracts or eliminates the problematic nitride film formation step from the manufacturing process by controlling the atmospheric conditions and processing parameters. By performing heat treatment in a controlled inert atmosphere at 1400-1600°C, the process achieves defect reduction without generating the nitride film that would require additional removal steps, thus removing this complexity from the manufacturing sequence.
3Productivity
If rapid heating/cooling is used to improve productivity, then productivity is improved, but slip generation increases
Solution Approach 1:
The patent optimizes the heating and cooling rates within specific ranges to prevent slip generation while maintaining rapid processing. By controlling the temperature change rate and peak temperature (1400-1600°C) within appropriate parameters, the process achieves rapid defect reduction without inducing thermal stress that would cause slip, thus resolving the contradiction between productivity and harmful factor generation.
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 grown-in defects, prevents slip, and enhances surface roughness of silicon wafers by forming a Denuded Zone layer that pins dislocations and prevents reprecipitation of oxygen, thereby improving the quality of silicon wafers for semiconductor devices.
Implementation Method 1
rapidly heating the silicon wafer to a first temperature of 1300° C. or higher and a melting point of silicon or lower
Implementation Method 2
rapidly cooling the silicon wafer from the first temperature at a first cooling rate
Implementation Method 3
forming a Denuded Zone layer that reduces defects and improves surface quality
Data Source
AI summary
In a manufacturing method for a silicon wafer, a first heat treatment process is performed on the silicon wafer while introducing a first gas having an oxygen gas in an amount of 0.01 vol. % or more and 1.00 vol. % or less and a rare gas, and a second heat treatment process is performed while stopping introducing the first gas and introducing a second gas having an oxygen gas in an amount of 20 vol. % or more and 100 vol. % or less and a rare gas. In the first heat treatment process, the silicon wafer is rapidly heated to first temperature of 1300° C. or higher and a melting point of silicon or lower at a first heating rate, and kept at the first temperature. In the second heat treatment process, the silicon wafer is kept at the first temperature, and rapidly cooled from the first temperature at a first cooling rate.