Wafer Defect Evaluation via Surface Photovoltage
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Solution Overview
Problem
Current methods for evaluating defects in silicon wafers, such as the CZ method, face challenges in accurately detecting and classifying crystal defects like V-rich, OISF, and I-rich zones, particularly due to limitations in existing particle counters and the need for additional thermal processes, which can be time-consuming and prone to contamination.
Innovation Solution
A method utilizing a surface photovoltage (SPV) technique with a deposited oxidation layer to measure minority carrier diffusion distances, allowing for the classification of defect zones like LDP, Pv, and Pi zones without degrading time zero dielectric breakdown properties, and enabling quick contamination confirmation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional equipment and processes are used to detect and classify crystal defects, then measurement precision is improved, but device complexity and loss of time increase
Solution Approach 1:
The patent replaces complex mechanical evaluation equipment and multiple process steps with a simplified measurement system that uses a single test structure and direct electrical measurements to detect and classify crystal defects, thereby reducing device complexity while maintaining measurement precision
Solution Approach 2:
The patent extracts the essential defect detection function from complex evaluation processes by using a simplified test structure that isolates the defect detection capability, allowing for precise measurement without requiring additional equipment
2Measurement precision
If multiple evaluation methods are used to classify crystal zones, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent merges multiple evaluation methods into a single integrated measurement process that simultaneously detects and classifies crystal zones using one test structure and correlated measurements, thereby reducing evaluation time while maintaining classification precision
Solution Approach 2:
The patent performs preliminary classification of crystal zones through direct electrical measurements that provide immediate zone identification, eliminating the need for sequential evaluation steps and reducing overall measurement time
3Difficulty of detecting and measuring
If conventional defect detection methods are used, then detection capability is improved, but reliability of TZDB properties deteriorates
Solution Approach 1:
The patent introduces a test structure as an intermediary that enables defect detection without directly interacting with the TZDB properties of the silicon wafer, thereby maintaining TZDB reliability while achieving defect detection capability
Solution Approach 2:
The patent uses a test structure that replicates the essential electrical characteristics of the silicon wafer, allowing defect detection through the copy structure without degrading the original wafer's TZDB properties
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 provides a simple, objective, and efficient method for evaluating wafer defects by classifying crystal zones and confirming contamination, reducing the need for complex preprocessing and equipment, while maintaining accurate results.
Implementation Method 1
forming an oxidation layer on the wafer sample
Implementation Method 2
measuring a diffusion distance of a minority carrier using a surface photovoltage (SPV) method
Data Source
AI summary
Provided is a method for evaluating defects in a wafer. The method for evaluating the wafer defects includes preparing a wafer sample, forming an oxidation layer on the wafer sample, measuring a diffusion distance of a minority carrier using a surface photovoltage (SPV), and determining results of a contamination degree.