Single-Crystal Silicon Wafer COP Evaluation Segmentation
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Solution Overview
Problem
Current COP evaluation methods for single-crystal silicon wafers lack objectivity and quantification, particularly for large-diameter wafers, leading to overly strict acceptance criteria that reduce production yield.
Innovation Solution
A method involving concentric radial division of the wafer into evaluation segments with set upper limit values for COPs, allowing for quantitative and objective assessment of COP patterns, distinguishing between crystal-induced and non-crystal-induced defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional COP evaluation methods are used, then acceptance determination can be made, but the evaluation lacks objectivity and quantification leading to overly strict criteria
Solution Approach 1:
The wafer surface is divided into multiple evaluation regions (central region and outer peripheral region) with different upper limit values for COP counts. This segmentation allows differentiated assessment standards across different areas of the wafer, enabling more objective and nuanced evaluation while reducing unnecessary rejections and improving production yield.
2Shape
If high pulling-up speed is used during crystal growth, then OSF ring area is spread to the whole wafer, but COP density increases
Solution Approach 1:
Different upper limit values are assigned to different evaluation regions based on their specific characteristics. The central region has a lower upper limit value (5 COPs) while the outer peripheral region has a higher upper limit value (10 COPs), reflecting the local quality differences in COP generation patterns and their impact on device performance.
3Reliability
If strict acceptance criteria are applied, then defect-free wafers are ensured, but production yield decreases due to unnecessary rejections
Solution Approach 1:
The evaluation criteria are changed from a single uniform standard to a multi-parameter system with region-specific upper limit values. This parameter change enables more flexible and accurate assessment of wafer quality, ensuring defect-free wafers are identified while reducing unnecessary rejections and improving production yield.
Data Source
AI summary
An evaluation area of an evaluation object wafer is concentrically divided in a radial direction, an upper limit value to the number of COPs is set in each divided evaluation segment, and an acceptance determination of the single-crystal silicon wafer is made using the upper limit value as a criterion. Thereby, a quantitative and objective COP evaluation can be made, and a proper determination is made based on a clear criterion. The evaluation method of the present invention can sufficiently deal with automation of the COP evaluation (inspection) and the higher-quality wafer in the near future, and the evaluation method can be widely applied to production of the single-crystal silicon wafer and production of a semiconductor device.