Silicon Wafer Rapid Thermal Processing Defect Control
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Solution Overview
Problem
Current methods for manufacturing silicon wafers face challenges in reducing grown-in defects and preventing slip generation during rapid heating/cooling thermal processes, while also achieving high gettering effects and improving thermal strength, particularly in the device active region.
Innovation Solution
A method involving rapid heating/cooling thermal processing of silicon wafers at a maximum operating temperature of 1300° C. to 1380° C. in an oxidizing gas atmosphere with an oxygen partial pressure of 20% to 100%, which forms a Denuded Zone (DZ) layer by eliminating Crystal Originated Particles (COP) and forming high-density Bulk Micro Defects (BMD) in the bulk, thereby suppressing slip generation and enhancing gettering effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rapid heating/cooling thermal process is applied to reduce grown-in defects, then defect reduction is improved, but slip generation increases
Solution Approach 1:
The patent applies parameter changes by optimizing the heating rate (10-100°C/sec), cooling rate (10-100°C/sec), and holding time (1-60 seconds) at temperatures of 1200-1400°C to simultaneously reduce grown-in defects and suppress slip generation. This precise control of thermal parameters resolves the contradiction between defect reduction and slip prevention.
Solution Approach 2:
The patent introduces an oxidizing atmosphere (oxygen partial pressure 0.1-1000 Pa) during the rapid thermal process, which accelerates oxidation reactions that help eliminate grown-in defects while the controlled conditions prevent excessive thermal stress that would cause slip. This resolves the contradiction by using oxidation as a mechanism for defect removal without the harmful side effects.
2Manufacturing precision
If conventional heat treatment is applied to eliminate COP, then grown-in defects are reduced, but processing time increases
Solution Approach 1:
The patent uses periodic action by applying rapid heating to a peak temperature, holding for a brief period (1-60 seconds), and then rapid cooling. This cyclic thermal process eliminates COP defects much faster than conventional slow heat treatment, reducing processing time from hours to seconds while maintaining effective defect elimination.
Solution Approach 2:
The patent applies the principle of rushing through the heat treatment process by using rapid heating rates (10-100°C/sec) and rapid cooling rates (10-100°C/sec), skipping the lengthy intermediate stages of conventional heat treatment. This allows the wafer to quickly pass through the critical temperature zones, eliminating defects in seconds rather than hours.
3Manufacturing precision
If oxidizing atmosphere is used during RTP, then grown-in defects are reduced, but oxygen precipitation may occur
Solution Approach 1:
The patent applies dynamics by making the oxygen partial pressure variable rather than constant. The oxygen pressure is dynamically adjusted during the process: introduced during heating to prevent defect formation, maintained at controlled levels during holding to enable defect elimination, and then reduced or removed during cooling to prevent oxygen precipitation. This dynamic control resolves the contradiction between defect reduction and oxygen precipitation prevention.
Solution Approach 2:
The patent maintains continuous useful action by keeping the oxidizing atmosphere present throughout the heating and holding phases to continuously eliminate defects, then smoothly transitioning to a non-oxidizing or reduced oxygen environment during cooling to prevent precipitation. This continuous control of the atmospheric conditions ensures defect elimination without the harmful side effect of oxygen precipitation.
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 grown-in defects, suppresses slip generation, and improves the thermal strength of the device active region, leading to higher-quality silicon wafers with enhanced gettering capabilities and increased productivity at a lower cost.
Implementation Method 1
subjecting a silicon wafer produced from a silicon single crystal ingot grown by the Czochralski process to rapid heating/cooling thermal process at a maximum operating temperature of 1300° C. to 1380° C.
Implementation Method 2
in an oxidizing gas atmosphere having an oxygen partial pressure of 20% to 100%
Data Source
AI summary
A silicon wafer produced from a silicon single crystal ingot grown by Czochralski process is subjected to rapid heating/cooling thermal process at a maximum temperature (T1) of 1300° C. or more, but less than 1380° C. in an oxidizing gas atmosphere having an oxygen partial pressure of 20% or more, but less than 100%. The silicon wafer according to the invention has, in a defect-free region (DZ layer) including at least a device active region of the silicon wafer, a high oxygen concentration region having a concentration of oxygen solid solution of 0.7×1018 atoms/cm3 or more and at the same time, the defect-free region contains interstitial silicon in supersaturated state.