Silicon Wafer Heat Treatment Void Defect Annihilation
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Solution Overview
Problem
Current methods for heat treating silicon single crystal wafers are costly and inefficient in annihilating void defects and micro oxide precipitate nuclei, particularly as they often require two-step processes and cannot fully eliminate defects throughout the wafer thickness.
Innovation Solution
A method involving a heat treatment in an oxidizing ambient, where the temperature, oxygen concentration, and crystal growth conditions are correlated to effectively annihilate void defects and micro oxide precipitate nuclei, using specific relational expressions to determine optimal treatment parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single crystal is grown with a relatively large growth rate, then productivity is improved, but void defects (vacancy type) are generated in the crystal
Solution Approach 1:
The patent applies preliminary action by performing a first heat treatment in a non-oxidizing ambient before the second heat treatment. This initial treatment prepares the crystal by creating conditions favorable for subsequent defect annihilation, allowing the use of higher growth rates while still achieving defect-free quality through the coordinated two-step thermal process
Solution Approach 2:
The patent utilizes parameter changes by varying the oxygen partial pressure and temperature through two distinct heat treatment stages. The first treatment uses low oxygen partial pressure (non-oxidizing) at elevated temperature, then transitions to high oxygen partial pressure (oxidizing) in the second treatment. These parameter changes enable effective annihilation of void defects while maintaining high productivity from faster crystal growth rates
2Reliability
If conventional two-step heat treatment processes are used to annihilate void defects, then defect annihilation effectiveness is improved, but manufacturing cost and process complexity increase
Solution Approach 1:
The patent merges the defect annihilation function with oxide film formation into a single second heat treatment step. By combining these two functions that were previously separate into one oxidizing ambient treatment, the process complexity is reduced while maintaining effective void defect annihilation and achieving additional benefits from oxide precipitate formation
Solution Approach 2:
The patent converts the typically harmful effect of oxygen (which can create oxide precipitates and potential defects) into a beneficial process. By intentionally introducing oxygen in the second heat treatment step, the patent achieves both void defect annihilation and controlled oxide precipitate formation that can serve as gettering sites for impurities, thereby converting a potential harm into a useful function
3Reliability
If heat treatment temperature is increased to annihilate void defects, then defect annihilation effectiveness is improved, but slip dislocation generation increases
Solution Approach 1:
The first heat treatment in non-oxidizing ambient performs preliminary action by preparing the crystal structure for defect annihilation without introducing oxygen. This preliminary preparation allows the subsequent oxidizing treatment to be more effective at lower temperatures, thereby annihilating void defects while avoiding the high temperatures that would generate slip dislocations
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 allows for the efficient and secure annihilation of void defects and micro oxide precipitate nuclei with reduced costs, while preventing slip dislocation generation, resulting in defect-free silicon single crystal wafers suitable for semiconductor devices.
Implementation Method 1
performing a heat treatment in an oxidizing ambient
Implementation Method 2
a heat treatment of a silicon single crystal wafer in an oxidizing ambient
Data Source
AI summary
A method for a heat treatment of a silicon single crystal wafer in an oxidizing ambient, including: performing the heat treatment based on a condition determined by a tripartite correlation between a heat treatment temperature during the heat treatment, an oxygen concentration in the silicon single crystal wafer before the heat treatment, and a growth condition of a silicon single crystal from which the silicon single crystal wafer is cut out. This provides a method for a heat treatment of a silicon single crystal wafer which can annihilate void defects or micro oxide precipitate nuclei in a silicon single crystal wafer with low cost, efficiently, and securely by a heat treatment in an oxidizing ambient.