Lithography Mask Overlay Alignment Using SEM Coordinate Compensation
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Solution Overview
Problem
Lithography machines face challenges in accurately calibrating and compensating for the first layer of a mask without a front-layer mask, leading to potential defects and inability to perform automatic alignment due to the lack of alignment marks, which affects the overlaying effect between different layers.
Innovation Solution
A lithography measurement machine equipped with a rotating base, image simulation unit, and scanning electron microscope (SEM), where the processor compares simulated and scanned coordinate information to perform compensation operations, ensuring masks are aligned correctly, thereby improving the overlaying effect between layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a lithography machine etches the first layer of a mask without a front-layer mask for calibration, then the lithography process can proceed, but the alignment precision deteriorates leading to potential defects
Solution Approach 1:
The patent applies preliminary action by pre-defining alignment marks on the first layer mask before etching. These alignment marks are prepared in advance to enable subsequent automatic alignment operations, eliminating the need for front-layer mask calibration while maintaining precision.
Solution Approach 2:
The patent introduces alignment marks as an intermediary element between the lithography machine and the mask layers. These marks serve as mediators that enable the lithography machine to perform automatic alignment and compensation operations without requiring a front-layer mask.
2Device complexity
If the lithography machine lacks alignment marks for automatic compensation, then the device structure remains simple, but the measurement precision deteriorates affecting overlaying effect
Solution Approach 1:
The patent uses alignment marks that are copied or replicated across different mask layers. These marks create a consistent reference framework that enables precise measurement and alignment without complicating the overall device structure.
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 solution enables precise alignment and compensation of masks, enhancing the overlaying effect and increasing product yield by ensuring masks are accurately positioned, thus addressing the calibration and alignment issues in lithography machines.
Implementation Method 1
a scanning electron microscope (SEM) is configured to scan the exposure area to obtain the second coordinate information
Data Source
AI summary
An operating method includes: placing a first mask, a second mask, a third mask and a fourth mask on a rotating base, in which each of the first, second, third and fourth masks has a first exposure unit, a second exposure unit, a third exposure unit and a fourth exposure unit; overlaying the first, second, third and fourth masks such that the first exposure unit of the first mask, the second exposure unit of the second mask, the third exposure unit of the third mask and the fourth exposure unit of the fourth mask are arranged adjacently to form an exposure area; simulating a first coordinate information according to the exposure area by an image simulation unit; scanning the exposure area, by a scanning electron microscope (SEM), to obtain a second coordinate information; and comparing the first coordinate information with the second coordinate information.