On-Wafer APT Specimen Preparation for Higher Mass Resolution
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Solution Overview
Problem
Current atom probe tomography (APT) techniques face limitations in achieving high mass resolution and accurate analysis of dopant distribution in semiconductor devices due to the use of specimens that are not directly formed on the wafer region under test, leading to potential mechanical instability and reduced analysis precision.
Innovation Solution
The APT specimen is directly formed integrally on a wafer region by first patterning a trench and bump structures using laser milling, followed by low-kV gas ion milling to sharpen the tips, creating a mechanically robust specimen with improved mass resolution without the need for welding materials or foreign coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If APT specimens are not directly formed on the wafer region under test, then the preparation process is simpler, but mechanical instability and reduced analysis precision occur
Solution Approach 1:
The patent merges the specimen formation process with the wafer structure by directly creating APT specimens on the wafer region under test using focused ion beam (FIB) milling. This integration eliminates the need for separate specimen preparation steps and foreign coupling materials, thereby improving mechanical stability and analysis precision while maintaining preparation simplicity through automated FIB processing.
Solution Approach 2:
The patent introduces a specialized mounting structure that serves as an intermediary between the wafer region and the APT specimen. This mounting structure provides mechanical support and stable coupling without requiring welding materials or foreign coupling, enabling direct formation of specimens on the wafer while maintaining both mechanical robustness and analysis precision.
2Measurement precision
If welding materials or foreign coupling are used to form APT specimens, then the specimen can be formed, but mass resolution is reduced
Solution Approach 1:
The patent extracts and eliminates welding materials and foreign coupling from the specimen formation process. By using direct FIB milling to create specimens on the wafer region, the method removes the need for additional materials that would contaminate the specimen and reduce mass resolution, while still achieving easy specimen formation through automated processing.
Solution Approach 2:
The patent replaces mechanical welding or coupling systems with a direct FIB milling approach. Instead of using mechanical fastening or bonding materials to attach specimens to the wafer, the FIB system directly mills the specimen structure from the wafer material itself, eliminating contamination and improving mass resolution while maintaining ease of manufacture.
3Strength
If conventional specimen preparation methods are used, then the process is established, but mechanical robustness is reduced
Solution Approach 1:
The patent combines the specimen formation and mounting steps into a single integrated FIB milling process. By directly creating the specimen on the wafer region with appropriate mounting features built-in, the method achieves superior mechanical robustness through direct material continuity while keeping the preparation process simple through automation.
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 enhances the mass resolution power of the APT specimen, enabling more accurate and reliable analysis of material composition with improved mechanical robustness and simplified preparation processes.
Implementation Method 1
first patterning a trench and bump structures using laser milling
Implementation Method 2
followed by low-kV gas ion milling to sharpen the tips
Implementation Method 3
ions are removed from a surface of an APT specimen through application of an electrical pulse, which is referred to as field evaporation
Data Source
AI summary
The disclosure is directed to techniques in preparing an atom probe tomography (“APT”) specimen. The disclosed techniques form an APT specimen or sample directly on a DUT region on a wafer. The APT specimen is formed integrally to the substrate or the support structure, e.g., a carrier, under the APT specimen. A laser patterning is conducted to form a trench in the DUT and one or more bump structures in the trench. The laser patterning is relatively coarse and forms a coarse surface texture on each of the bump structures. A low-kV gas ion milling using a dual-beam focused ion beam (“FIB”) microscopes is then conducted to shape the bump structures into APT specimen.