Coaxial Reticle Alignment Device for Lithography
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing reticle alignment systems in lithography machines face challenges with accuracy due to reticle thickness tolerance, leading to increased structural complexity and potential detector damage from high exposure light sources, especially in packaging lithography machines.
Innovation Solution
A coaxial reticle alignment device with dedicated illumination modules and a shared image detection and processing module under the reticle, using a reference mark on the workpiece stage to derive relative positional information between reticle alignment marks and the reference mark, allowing for efficient alignment without relying on the exposure light source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reticle mark alignment system is disposed above the reticle with a glass plate, then the alignment system can image and detect reticle marks, but the structural complexity increases due to the need for depth of focus mechanisms to account for reticle thickness tolerance
Solution Approach 1:
The patent inverts the conventional alignment system configuration by moving the alignment system from above the reticle to below the reticle. This inversion eliminates the need for depth of focus mechanisms and vertical focusing systems, thereby reducing structural complexity while maintaining alignment accuracy through direct imaging of reticle marks without interference from glass plates or thickness variations
2Device complexity
If the reticle mark alignment system is arranged under the reticle to directly image marks, then structural complexity is reduced, but the reticle stage must be made larger to accommodate the alignment system
Solution Approach 1:
The patent merges the alignment system with the workpiece stage by integrating the alignment light source and detection components into the workpiece stage structure. This merging allows the alignment system to share the stage area, eliminating the need for additional space that would otherwise be required for a separate alignment system, thereby maintaining compact dimensions while reducing structural complexity
3Productivity
If the exposure light source is used for reticle alignment in packaging lithography machines, then alignment can be accomplished, but detector damage and lowered measurement accuracy occur due to high exposure dosage
Solution Approach 1:
The patent segments the lighting system into separate functional components: a dedicated low-intensity alignment light source for reticle alignment and a high-intensity exposure light source for pattern transfer. This segmentation allows the alignment function to be performed with minimal light intensity, preventing detector damage while maintaining alignment efficiency, and clearly separates the alignment and exposure functions
4Measurement precision
If two sets of imaging lenses and detectors are used in the workpiece stage for imaging and detection of reticle marks, then alignment can be performed, but the structure becomes complicated and expensive
Solution Approach 1:
The patent implements multi-functionality by designing the imaging lenses and detectors in the workpiece stage to serve dual purposes: they are used both for the main exposure function and for reticle alignment detection. This universal use of components eliminates the need for separate dedicated alignment imaging systems, thereby reducing structural complexity and cost while maintaining alignment measurement accuracy through the same optical path
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 minimizes errors from reticle thickness tolerance, reduces structural complexity, and enhances alignment efficiency by simultaneous imaging of reticle and reference marks, while avoiding detector damage from high exposure light.
Implementation Method 1
an illumination module, configured to irradiate an alignment light beam onto a reticle alignment mark on the reticle
Implementation Method 2
a projection objective, disposed under the reticle and configured to image the reticle alignment mark
Data Source
AI summary
A coaxial reticle alignment device, a lithography apparatus and alignment methods are disclosed. The coaxial reticle alignment device includes: illumination modules (A, B), each configured to provide an alignment light beam; a projection objective (8) under a reticle (5); a reference plate (9) on a workpiece stage (12), configured to carry a reference mark (10); and an image detection and processing module (11) under the reference plate (9). The reference mark (10) is located within a FOV of the image detection and processing module (11), and during movement of the workpiece stage (12), the image detection and processing module (11) receives the alignment light beam having passed sequentially through the reticle alignment mark (6, 7), the projection objective (8) and the reference mark (10), it captures images of the reticle alignment mark (6, 7) and the reference mark (10) which are processed to derive relative positional information between the reticle alignment mark (6, 7) and the reference mark (10) that enables the alignment of the reticle (5) with the workpiece stage (12). The coaxial reticle alignment device adopts dedicated separate illumination means, has a simple structure, allows easy operation and improves alignment efficiency.