Monocrystalline Silicon Wafer Defect Classification Using LST
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Solution Overview
Problem
Existing methods for detecting defects in silicon wafers are time-consuming, costly, and impose stringent requirements on wafer preparation, particularly in region classification for defect assessment.
Innovation Solution
A method utilizing laser scattering tomography (LST) to measure particles in as-grown silicon wafers, followed by a thermal treatment and subsequent LST measurements to determine V-rich, Pv, I-rich, and Pi regions based on preset density or size values, reducing the need for complex pre-treatments and lowering process costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If vapor etching combined with localized light scattering scanning is used for defect detection, then defect identification capability is improved, but process complexity and time consumption increase due to required pre-treatment steps
Solution Approach 1:
The patent extracts the essential defect detection function from the complex vapor etching process, using LST to directly measure particle density and size in the as-grown wafer without requiring vapor etching pre-treatment. This separates the detection function from the preparation steps, eliminating the need for complex pre-treatment while maintaining defect identification capability.
Solution Approach 2:
The patent replaces the mechanical/chemical vapor etching process with an optical measurement system (LST). Instead of using vapor etching to reveal defects, the system uses laser scattering tomography to directly detect and characterize particles, substituting a complex chemical process with a non-contact optical measurement method.
2Measurement precision
If conventional LST with oxygen precipitate growth is used for defect assessment, then measurement capability is improved, but processing time and cost increase due to multiple heat treatment steps
Solution Approach 1:
The patent performs preliminary measurement of particle density and size in the as-grown wafer before any heat treatment. By measuring the defect characteristics directly in their as-grown state, the system eliminates the need for subsequent heat treatment steps to develop oxygen precipitates, thereby reducing processing time while maintaining measurement precision.
Solution Approach 2:
The patent changes the measurement parameters from indirect oxygen precipitate density (requiring heat treatment) to direct particle density and size measurement. This parameter change allows the system to detect defects in their as-grown state without requiring the time-consuming heat treatment process to develop visible precipitates.
3Manufacturing precision
If region classification for defect assessment is performed, then defect characterization accuracy is improved, but wafer preparation requirements become more stringent
Solution Approach 1:
The patent enables the wafer to serve itself by measuring defect characteristics directly in the as-grown state without requiring external pre-treatment steps. The LST system automatically characterizes particles based on their inherent properties (density and size), eliminating the need for complex preparation procedures while maintaining accurate defect characterization.
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
The method provides accurate, efficient, and cost-effective characterization of defect regions in silicon wafers with high robustness and repeatability, significantly reducing thermal treatment time and complexity.
Implementation Method 1
measuring particles in an as-grown silicon wafer by using LST to obtain a first measurement
Implementation Method 2
subjecting the silicon wafer to a thermal treatment, measuring particles in the silicon wafer by using LST again
Data Source
AI summary
The present invention provides a method for determining the type of defects in a monocrystalline silicon wafer, which includes the steps of: using LST to measure particles in an as-grown silicon wafer and thereby obtaining a first measurement, and determining a V-rich region based on the first measurement and a first preset density value; and subjecting the silicon wafer to a thermal treatment, again using LST to measure particles in the silicon wafer and thereby obtaining a second measurement, and determining a Pv region, an I-rich region and a Pi region based on the second measurement, a second preset density value and a third preset density value. As a result, a particle density can be utilized as a basis for accurately and efficiently determining a region of interest of a monocrystalline silicon wafer as one of a V-rich region, a Pv region, a Pi region and an I-rich region.