Specimen Alignment Using 2D Multi-Channel Image Rotation
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Solution Overview
Problem
Current methods for aligning specimens with inspection tools suffer from false alignment issues, low accuracy, and slow speed due to limitations in one-dimensional projection and two-dimensional optical image alignment techniques, leading to errors in defect detection and process control.
Innovation Solution
A system and method utilizing a computer-implemented approach that acquires two-dimensional images from a detector, determines offsets and angles, and adjusts the specimen's orientation using multi-channel images, allowing for precise alignment by rotating the specimen until the desired angle is achieved, thereby improving alignment accuracy and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If 1D projection-based alignment method is used, then alignment process is simplified, but false alignment issues occur and measurement precision deteriorates
Solution Approach 1:
The patent transitions from 1D projection-based alignment to 2D image-based alignment. By utilizing two-dimensional images instead of one-dimensional projections, the system captures more spatial information about the specimen features, enabling more accurate alignment calculations while avoiding false alignment issues that occur with 1D projections.
Solution Approach 2:
The patent changes the fundamental parameter used for alignment from 1D projection data to 2D image data. This parameter change allows the system to compute alignment based on richer spatial information, improving measurement precision while maintaining computational feasibility through efficient image processing algorithms.
2Measurement precision
If 2D optical image alignment method is used, then alignment accuracy improves, but alignment speed deteriorates
Solution Approach 1:
The patent performs preliminary actions by acquiring multiple images at different focal depths before final alignment computation. By pre-acquiring defocused images and computing their differences, the system prepares alignment data in advance, which speeds up the final alignment determination while maintaining high measurement precision.
Solution Approach 2:
The patent skips intermediate steps by directly computing alignment from 2D image differences without requiring separate focus metrics acquisition for each die. This approach rushes through the alignment process by using pre-acquired multi-focus images, significantly improving alignment speed while maintaining accuracy.
3Device complexity
If single channel image is used for alignment, then device complexity is reduced, but alignment reliability deteriorates due to inability to image both horizontal and vertical patterns
Solution Approach 1:
The patent makes the imaging system universal by using multiple channels (e.g., P-channel and N-channel) that can each image different pattern orientations. This multi-functionality allows the system to reliably align specimens with various pattern types (horizontal, vertical, diagonal) without requiring separate imaging systems, improving alignment reliability while maintaining reasonable device complexity.
Solution Approach 2:
The patent merges information from multiple channels by combining images from P-channel and N-channel detectors. This combination allows the system to capture both horizontal and vertical patterns in a unified alignment process, improving reliability by ensuring all pattern types are accounted for while avoiding the need for separate alignment procedures.
4Measurement precision
If 2D optical image alignment is performed by moving to the same spot in every die, then measurement precision improves, but productivity deteriorates due to slow acquisition speed
Solution Approach 1:
The patent implements periodic action by acquiring images at multiple fixed focal depths in a systematic sequence. This periodic imaging approach ensures consistent sampling of the specimen at different focus levels, improving measurement precision through structured data collection while maintaining productivity by using a regular, efficient acquisition pattern.
Solution Approach 2:
The patent maintains continuity of useful action by acquiring multiple images in rapid succession at different focal depths without moving the stage between acquisitions. This continuous imaging process captures all necessary alignment data in one location, improving precision through multi-focus information while maintaining high throughput by eliminating mechanical movements.
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 alignment accuracy and speed, reducing errors in defect detection and improving the reliability of inspection results by using multi-channel images and precise angle determination, leading to better process control and higher inspection tool effectiveness.
Implementation Method 1
a detector configured to detect energy from the specimen and to generate output responsive to the detected energy
Data Source
AI summary
Methods and systems for setting up alignment of a specimen are provided. One system includes computer subsystem(s) configured for acquiring two-dimensional (2D) images generated from output of a detector of an output acquisition subsystem at template locations in corresponding areas of printed instances on a specimen. The computer subsystem(s) determine offsets in x and y directions between the template locations using the 2D images and determine an angle of the specimen with respect to the output acquisition subsystem based on the offsets. If the angle is greater than a predetermined value, the computer subsystem(s) rotate the specimen and repeat the steps described above. If the angle is less than the predetermined value, the computer subsystem(s) store one of the 2D images for alignment of the specimen in a process performed on a specimen. The 2D images may include multi-mode images, which may be fused prior to determining the offsets.