LEED Ptychography Surface Profiling for Wafer Defect Inspection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing imaging technologies struggle to accurately inspect complex semiconductor structures with high-aspect-ratio features and low-contrast materials, such as 3D NAND devices, due to limitations in resolution and damage from high-energy electrons, necessitating improved non-destructive imaging methods for defect detection and surface profiling.
Innovation Solution
Combining low-energy-electron diffraction (LEED) with ptychography to generate diffraction patterns from a coherent electron beam, allowing for lensless imaging and computational reconstruction of surface profiles, including phase information, to detect defects and characterize semiconductor wafer structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional scanning electron microscope (SEM) is used for imaging, then high-resolution imaging can be achieved, but high-energy electrons cause deterioration and damage to the sample surface
Solution Approach 1:
The patent changes the energy parameter of the electron beam from high energy (traditional SEM) to low energy (1-100 eV), transforming the imaging mechanism from direct high-energy electron interaction to low-energy electron diffraction. This parameter change enables non-destructive imaging while maintaining measurement capability through diffraction pattern analysis
Solution Approach 2:
The patent replaces the mechanical scanning and direct imaging mechanism of traditional SEM with a diffraction-based measurement system. Instead of directly forming images through electron beam scanning, the system uses low-energy electron diffraction patterns and computational algorithms (ptychography) to reconstruct surface information, substituting mechanical imaging with wave-based diffraction and computational reconstruction
2Reliability
If optical microscopes or charged particle beam microscopes are used for inspection, then defect detection capability is provided, but accuracy and throughput decrease for complex structures with high-aspect-ratio features
Solution Approach 1:
The patent transitions from two-dimensional projection imaging to three-dimensional surface profiling by utilizing low-energy electron diffraction. The diffraction patterns contain out-of-plane information that enables reconstruction of surface topography and height profiles, adding a vertical dimension to the inspection capability and improving detection accuracy for 3D structures
Solution Approach 2:
The patent introduces low-energy electron diffraction patterns as an intermediary between the electron beam and the final image. Instead of direct beam-sample interaction producing images, the diffraction patterns serve as intermediate data that is processed through ptychography algorithms to generate surface profile information, enabling non-destructive 3D imaging
3Loss of information
If coherent electron beam is used for LEED and ptychography, then phase information and surface profile data can be obtained, but device complexity increases due to coherence requirements
Solution Approach 1:
The patent employs self-service by using the diffraction pattern itself to provide the information needed for phase retrieval. The ptychography algorithm iteratively refines the phase information by comparing measured diffraction patterns with calculated patterns from trial wavefunctions, allowing the system to extract phase information without requiring additional phase-contrast imaging hardware or complex interferometric setups
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
Enables high-resolution, non-destructive imaging of semiconductor surfaces, detecting defects like scum defects and characterizing nanoscale electric fields, with improved accuracy and throughput, suitable for complex structures that traditional SEMs cannot effectively inspect.
Implementation Method 1
A LEED pattern can be generated from the interaction of a relatively localized coherent electron beam incident on the sample surface
Implementation Method 2
phase information can also be reconstructed from the diffraction patterns, which includes valuable information related to the height/depth profile of the sample surface
Data Source
Figure 1
Figure 2
Figure 3
AI summary
In low-energy-electron diffraction (LEED), electron diffraction patterns are measured, and no projection or imaging lenses are present to form an image of a sample surface. Instead, an image may be formed based on a series of electron diffraction patterns from electrons reflected and diffracted from the sample surface. A LEED diffraction pattern out of this series of diffraction patterns can be generated from the interaction of a relatively localized coherent electron beam incident on the sample surface. Phase information from the diffraction pattern can be used to determine (or reconstruct) structures on the sample surface. Advantageously, LEED is used in combination with ptychography (to generate a series of diffraction patterns which are each associated with a given particle beam position, where particle beams centered at neighboring positions are partially overlapping) to determine semiconductor wafer surface structures through lensless imaging for defect inspection and/or other purposes.