Semiconductor Wafer Metal Contamination Evaluation
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Solution Overview
Problem
Current methods for evaluating metal contamination in semiconductor wafers after heat treatment are unreliable due to interference from internal oxygen precipitates and minute defects, making it difficult to accurately determine localized metal contamination.
Innovation Solution
A method that analyzes multiple points on the wafer using either decreasing or increasing analysis values with metal contamination, employing probability distribution functions to identify abnormal values and determine the presence or absence of localized contamination, using techniques like µ-PCD or SPV methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If lifetime measurement or diffusion length measurement is used to evaluate metal contamination, then metal contamination can be detected, but internal oxygen precipitates and minute defects also decrease these values causing false positive results
Solution Approach 1:
The patent divides the wafer surface into multiple measurement regions and performs separate statistical analysis on each region. By segmenting the measurement data by spatial location, the method can identify localized contamination events distinct from widespread defect patterns, resolving the contradiction between detection sensitivity and reliability.
Solution Approach 2:
The patent applies different evaluation criteria to different regions of the wafer based on local characteristics. By analyzing the spatial distribution and density of measurement values across different regions, the method can distinguish between localized metal contamination and uniform defect patterns caused by oxygen precipitates, thereby improving both detection accuracy and evaluation reliability.
2Measurement precision
If the number of measurement points is increased to improve statistical analysis, then evaluation precision improves, but measurement time and cost increase
Solution Approach 1:
The patent performs measurements at a sufficient number of points to achieve statistical significance for localized region analysis, rather than exhaustive full-wafer coverage. By focusing measurements on regions where contamination is most likely to occur and performing targeted statistical analysis, the method achieves high evaluation precision without excessive measurement time or cost.
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 precise evaluation of localized metal contamination, reducing false positives and negatives by focusing on abnormal values and accounting for factors like diffusion lengths and defect densities, ensuring high-quality semiconductor wafers are shipped without contamination.
Implementation Method 1
a first analysis method in which analysis values employed in evaluation decrease as an amount of contamination by a metal element that is to be evaluated increases
Implementation Method 2
a second analysis method in which analysis values employed in evaluation increase as an amount of contamination by a metal element that is to be evaluated increases
Implementation Method 3
contamination in the form of diffusion in the vicinity of contact portions during heat treatment by metal impurities that adhere to the semiconductor wafer due to contact with a contamination source
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
An aspect of the present invention relates to a method of evaluating metal contamination in a semiconductor wafer that has been subjected to a heat treatment, which comprises obtaining analysis values by analyzing a plurality of analysis points on a surface of the semiconductor wafer by a first analysis method or a second analysis method, wherein in the first analysis method, analysis values employed in evaluation decrease as an amount of contamination by a metal element that is to be evaluated increases, and in the second analysis method, analysis values employed in evaluation increase as an amount of contamination by a metal element that is to be evaluated increases, and wherein determination of presence or absence of localized contamination by the metal element that is to be evaluated is made by evaluating the analysis values based on the normal value specified by a probability distribution function.