Iron-Implanted Semiconductor Wafer Calibration Standard
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Solution Overview
Problem
Iron contamination during silicon device manufacturing leads to oxide degradation and device malfunctions, as it creates deep-level recombination centers and reduces carrier lifetime, and existing methods for tracking iron contamination are limited in accuracy and effectiveness, especially as thermal budgets are reduced.
Innovation Solution
A method of preparing an iron-implanted semiconductor wafer by implanting iron through different regions of the wafer surface at varying densities and annealing it to diffuse iron into the bulk, allowing for precise calibration standards for surface photovoltage iron mapping and other evaluation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If iron implantation is performed at high density across the entire wafer surface, then the calibration standard coverage is improved, but the cost and process complexity increase
Solution Approach 1:
The wafer surface is divided into multiple discrete regions, each receiving a specific iron implantation density. This segmentation allows creation of a calibration standard with multiple known iron concentration levels across different regions, enabling accurate measurement calibration without requiring uniform high-density implantation across the entire wafer, thus reducing overall process complexity while maintaining measurement precision.
Solution Approach 2:
Different regions of the wafer are implanted with different iron densities tailored to specific calibration needs. This local quality approach ensures that each region has the appropriate iron concentration for its intended measurement purpose, optimizing measurement precision in each zone while avoiding unnecessary high-density implantation in regions where lower concentrations suffice, thereby reducing overall process complexity and cost.
2Manufacturing precision
If thermal processing time is extended to ensure complete iron diffusion, then the calibration standard uniformity is improved, but the productivity decreases
Solution Approach 1:
The wafer is divided into regions with pre-calculated implantation densities that account for expected diffusion patterns. This preliminary action allows shorter thermal processing times because the initial non-uniform distribution is already optimized to achieve the desired final uniform concentration profile after diffusion, rather than requiring extended processing to correct poor initial distribution.
Solution Approach 2:
The implantation energy and density parameters are varied across different regions to compensate for differences in diffusion rates. By adjusting these parameters beforehand, the patent achieves uniform iron distribution after a standardized, reduced thermal processing time, thereby improving productivity while maintaining manufacturing precision.
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 enables accurate measurement and calibration of iron contamination, improving the accuracy of iron detection and reducing device failures by providing a reliable calibration standard for various evaluation techniques, ensuring consistent and repeatable results across multiple wafers.
Implementation Method 1
implanting iron through at least two different regions of a front surface of the semiconductor wafer
Implementation Method 2
annealing the iron-implanted semiconductor wafer at a temperature and duration sufficient to diffuse implanted iron into the bulk region
Data Source
AI summary
A method of preparing an iron-implanted semiconductor wafer for use in surface photovoltage iron mapping and other evaluation techniques. A semiconductor wafer is implanted with iron through the at least two different regions of the front surface of the semiconductor at different iron implantation densities, and the iron-implanted semiconductor wafer is annealed at a temperature and duration sufficient to diffuse implanted iron into the bulk region of the semiconductor wafer.