Platelike Workpiece Alignment Mark with Directional Indicators
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Solution Overview
Problem
The detection of alignment marks in semiconductor wafer processing is hindered by significant transfer errors, causing the marks to fall outside the visual field of imaging means, leading to increased operation time and cost due to the need for multiple cameras with different magnifications.
Innovation Solution
A platelike workpiece with alignment marks surrounded by direction indicating marks, ensuring at least two of these marks fall within the visual field, allowing for quick and accurate alignment even with single high-magnification imaging, eliminating the need for multiple cameras.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single high-magnification imaging means is used for alignment mark detection, then measurement precision is improved, but the visual field becomes too narrow to accommodate alignment marks when transfer errors occur
Solution Approach 1:
The alignment mark is segmented into multiple directional indicating marks (first, second, third, fourth marks) arranged in different directions around the central alignment mark. This segmentation allows the imaging means to detect at least one directional indicating mark even when the central alignment mark falls outside the visual field due to transfer errors, while maintaining high magnification for precise detection.
2Area of stationary object
If multiple infrared cameras with different magnifications are used for alignment, then both wide visual field and high precision detection are achieved, but device complexity and cost increase
Solution Approach 1:
A single imaging means is designed to perform multiple functions: it can detect both the central alignment mark for high-precision alignment and the directional indicating marks for locating the alignment mark within the visual field. This eliminates the need for multiple cameras with different magnifications while maintaining both wide effective coverage and high detection precision.
3Reliability
If alignment marks are placed outside the visual field due to transfer errors, then alignment cannot be performed, but operator intervention to relocate marks increases operation time
Solution Approach 1:
Directional indicating marks are pre-positioned around the central alignment mark in four different directions at predetermined intervals. These marks are placed in advance to cover the maximum expected transfer error range, so that regardless of how much the stage is displaced, at least one directional indicating mark remains within the visual field to guide the operator back to the alignment mark.
Data Source
AI summary
A platelike workpiece having an alignment mark formed on the front side thereof and adapted to be recognized by an imaging unit included in an alignment apparatus for performing alignment. The platelike workpiece includes a plurality of direction indicating marks formed at given intervals so as to surround the alignment mark. Each of the direction indicating marks is pointed toward the alignment mark. The space of the direction indicating marks is set so that at least two of the plural direction indicating marks fall in the visual field of the imaging unit in viewing the platelike workpiece from the imaging unit.