Single-Crystal Silicon Ingot Thermal Profile for BMD Density
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Solution Overview
Problem
The challenge is to achieve high bulk microdefect (BMD) density in silicon wafers for semiconductor devices, as existing methods like nitrogen doping and heat treatment are either ineffective or costly, and result in peripheral oxidation-induced stacking faults and metal contamination.
Innovation Solution
A crystal puller with a cylindrical heating and cooling apparatus is used to control the temperature and cooling speed of the single-crystal silicon ingot, maintaining a V/G ratio between 1.1 and 1.2 times the critical value, allowing the ingot to be heat-treated between 600° C. and 800° C. and rapidly cooled, facilitating BMD nucleation and growth without nitrogen doping or additional heat treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nitrogen doping is used to increase BMD density, then BMD density is improved, but metal contamination and peripheral oxidation-induced stacking faults occur
Solution Approach 1:
The patent changes the temperature parameter during the pulling process, implementing a specific temperature profile that includes a heat treatment stage (600-800°C) followed by rapid cooling. This temperature parameter change enables BMD nucleation and growth without requiring nitrogen doping, thereby avoiding metal contamination and stacking faults while achieving the required BMD density of 1×10^8/cm³
2Quantity of substance
If extensive heat treatment is applied to achieve high BMD density, then BMD density is improved, but production cost and process complexity increase
Solution Approach 1:
The patent merges the heat treatment process with the crystal pulling process itself. The heating apparatus and cooling apparatus are integrated into the pulling system, allowing temperature control and rapid cooling to be performed in-situ during pulling. This eliminates the need for separate post-pulling heat treatment steps, reducing process complexity while achieving high BMD density
Solution Approach 2:
The patent performs BMD nucleation and growth during the pulling process itself rather than as a subsequent step. By implementing the heat treatment (600-800°C) and rapid cooling sequence during pulling, the BMDs are formed in advance within the ingot structure, eliminating the need for extensive post-processing heat treatments and reducing overall process complexity
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 ensures a BMD density of 1×10^8/cm^3 in epitaxial silicon wafers, meeting customer specifications without nitrogen doping or extensive heat treatment, thereby improving the quality and reducing costs.
Implementation Method 1
pulling the single-crystal silicon ingot upwardly in a vertical direction at a predetermined pulling speed V into the heat treatment chamber defined by the heating apparatus to be heat-treated
Implementation Method 2
continuing pulling the heat-treated single-crystal silicon ingot upwardly in the vertical direction at the predetermined pulling speed V into the cooling chamber defined by the cooling apparatus to be cool-treated
Implementation Method 3
facilitating BMD nucleation and growth without nitrogen doping or additional heat treatments
Data Source
AI summary
A crystal puller for pulling a single-crystal silicon ingot includes a cylindrical heating apparatus and a cylindrical cooling apparatus. The heating apparatus is located above a water cooling jacket, and is configured such that a single-crystal silicon ingot enters a heat treatment chamber defined by the heating apparatus to be heat-treated when the single-crystal silicon ingot moves upwardly in a vertical direction. The cooling apparatus is located above the heating apparatus, and is configured such that the heat-treated single-crystal silicon ingot enters a cooling chamber defined by the cooling apparatus to be cool-treated when the single-crystal silicon ingot continues moving upwardly in the vertical direction.