Focused Ion Beam Cross-Section Milling with Multi-Frame Scanning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current cross-section milling methods in semiconductor wafers face challenges with re-deposition issues, leading to inaccurate observations and increased processing time due to surface charging and material re-deposition artifacts.
Innovation Solution
A method involving coarse and fine scanning with distinct milling parameters, including varying beam spot sizes, pixel overlapping, and line-interlace mode, to reduce re-deposition and enhance accuracy and efficiency in cross-section milling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional single-frame milling is used, then processing time is reduced, but re-deposition artifacts increase and accuracy decreases
Solution Approach 1:
The milling process is divided into multiple frames (first frame, second frame, third frame) with different scanning patterns and parameters. Each frame performs a specific function: initial milling, re-deposition removal, and final precision milling. This segmentation allows optimization of each stage without compromising overall efficiency.
Solution Approach 2:
The method employs periodic scanning patterns across multiple frames, where each frame uses different scanning parameters (spot size, scanning speed, overlapping) to systematically remove re-deposited material while maintaining the underlying cross-section structure.
2Productivity
If larger beam spot size is used, then processing speed increases, but milling precision decreases
Solution Approach 1:
The beam spot size is dynamically adjusted across different frames and scanning lines. Larger spot sizes are used in earlier frames for rapid material removal, while smaller spot sizes are used in later frames for precision work and re-deposition removal, optimizing both speed and precision at different stages.
Solution Approach 2:
Multiple scanning parameters including beam spot size, scanning speed, and frame overlap are changed between frames to adapt to different milling stages. This parameter variation allows the system to achieve high productivity in initial stages while maintaining precision in final stages.
3Reliability
If pixel overlapping is increased, then surface coverage improves, but re-deposition artifacts increase
Solution Approach 1:
The scanning pattern uses periodic framing with controlled overlap between frames. The overlap is optimized to ensure complete surface coverage while allowing sufficient time for material removal and preventing excessive re-deposition by spacing frames appropriately.
Solution Approach 2:
The multiple-frame approach maintains continuous milling action across the entire cross-section area, ensuring no regions are missed while systematically removing re-deposited material through the sequence of frames with appropriate overlapping.
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 multi-frame scanning approach significantly reduces re-deposition artifacts, allowing for deeper and more accurate cross-section milling with reduced processing time, enabling better inspection and analysis of semiconductor wafers.
Implementation Method 1
Focused ion beam (FIB) system is one of the primary tools for examining, analyzing, and repairing processing layers while fabricating of integrated circuits. FIB systems facilitate analyzing defects on in-process wafers as well later diagnosing and correcting the process when a defect does occur.
Implementation Method 2
Current cross-section milling methods in semiconductor wafers face challenges with re-deposition issues, leading to inaccurate observations and increased processing time due to surface charging and material re-deposition artifacts.
Data Source
AI summary
A method of milling a cross section of a wafer and a milling device. The method includes a coarse scanning of at least two milling frames and a fine scanning of at least one milling frame. The milling device is adapted to cross-section milling of a wafer, said milling includes a coarse scanning of at least two milling frames and a fine scanning of at least one milling frame.