Compact Alignment Sensor Using Coherent Self-Imaging
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Solution Overview
Problem
Current alignment sensors in lithographic apparatuses are unable to measure intra-field distortions and support finer alignment grating pitches, and they typically measure only one alignment mark at a time, leading to inefficiencies in alignment precision and throughput.
Innovation Solution
A system that uses spatially coherent radiation to create self-images of alignment marks, which are then manipulated and combined to provide information on the position and intra-mark distortion, utilizing multimode interference devices and optical fibers to enable simultaneous measurement of multiple alignment marks and finer grating pitches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional alignment sensors are used to measure alignment marks, then the system can achieve basic alignment functionality, but it cannot measure intra-field distortions or support finer alignment grating pitches
Solution Approach 1:
The patent changes the illumination parameters by using spatially coherent radiation at specific angles (including oblique angles) to illuminate the alignment marks. This parameter change enables the creation of self-images that reveal intra-field distortions and allows measurement of finer grating pitches that conventional sensors cannot detect
Solution Approach 2:
The patent introduces a new dimension to alignment measurement by creating self-images through coherent illumination. This dimensional approach allows simultaneous measurement of position and distortion by analyzing the self-image characteristics, rather than relying on direct conventional sensing methods
2Productivity
If conventional alignment sensors measure one alignment mark at a time, then the system maintains simplicity, but it results in inefficiencies in alignment precision and throughput
Solution Approach 1:
The patent merges multiple measurement functions into a single sensor system. By using coherent illumination to create self-images, the system simultaneously measures the position and intra-field distortions of multiple alignment marks, combining what were previously separate measurement tasks into one integrated process
Solution Approach 2:
The alignment sensor is designed with multi-functionality to perform various measurement tasks simultaneously. The same sensor system can measure alignment mark positions, detect intra-field distortions, and support different grating pitches, making it a universal measurement tool that improves both throughput and precision
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 solution allows for compact, high-precision alignment with the ability to measure multiple alignment marks simultaneously, improving overlay accuracy and reducing processing time, while supporting grating pitches smaller than 1 um and addressing intra-field distortion.
Implementation Method 1
a periodic alignment mark is illuminated with spatially coherent radiation to create self images of the alignment mark
Implementation Method 2
utilizing multimode interference devices and optical fibers to enable simultaneous measurement of multiple alignment marks
Data Source
AI summary
An apparatus and system for determining alignment of a substrate in which a periodic alignment mark is illuminated with spatially coherent radiation which is then provided to a compact integrated optical device to create self images of the alignment mark which may be manipulated (e.g., mirrored, polarized) and combined to obtain information on the position of the mark and distortions within the mark. Also disclosed is a system for determining alignment of a substrate in which a periodic alignment mark is illuminated with spatially coherent radiation which is then provided to an optical fiber arrangement to obtain information such as the position of the mark and distortions within the mark.