On-Wafer APT Specimen Preparation for Mass Resolution and Stability
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Solution Overview
Problem
Existing atom probe tomography (APT) techniques face challenges in efficiently and accurately analyzing dopant concentration and distribution in semiconductor devices due to limitations in specimen preparation methods, which can lead to reduced mass resolution power and mechanical instability.
Innovation Solution
The method involves forming an APT specimen directly on a wafer region by laser patterning to create trenches and bump structures, followed by low-kV focused ion beam milling to sharpen the tips, ensuring the specimen is integrally formed without welding materials, thereby improving mass resolution power and mechanical robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional specimen preparation methods are used, then the analysis of dopant concentration and distribution can be performed, but the mass resolution power is reduced and mechanical instability occurs
Solution Approach 1:
The specimen preparation is segmented into distinct stages: laser patterning to create the basic bump structure, followed by FIB milling to refine the tip geometry. This segmentation allows each process to be optimized independently, with laser patterning providing robust mechanical support and FIB milling providing precise geometric control for mass resolution.
Solution Approach 2:
The laser patterning process performs preliminary shaping of the specimen, creating the bump structure that provides mechanical stability before the FIB milling process refines the tip geometry. This preliminary action ensures that the specimen has adequate mechanical support before undergoing the more aggressive FIB milling process.
2Measurement precision
If laser patterning and FIB milling are used to form the specimen, then the mass resolution power is improved, but the device complexity increases
Solution Approach 1:
The laser patterning process performs multiple functions: it creates the bump structure, defines the specimen location on the wafer, and provides mechanical support. This multi-functionality reduces the need for additional preparation steps and simplifies the overall process despite the advanced techniques used.
3Strength
If the specimen is formed integrally without welding materials, then the mechanical robustness is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent replaces mechanical welding or bonding processes with direct laser patterning and FIB milling to form the specimen integrally. This substitution eliminates the need for welding materials and associated precision requirements, while the laser and FIB processes provide sufficient precision through their inherent control mechanisms.
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 improved APT specimen achieves enhanced mass resolution power and mechanical stability, enabling more accurate and reliable analysis of semiconductor materials.
Implementation Method 1
A trench is formed within a first surface region of the semiconductor structure and a bump structure is formed in the trench
Implementation Method 2
low-kV focused ion beam 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.