IC Overlay Mark Using X-Y Dipole Exposure Segmentation
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Solution Overview
Problem
Conventional overlay marks in IC fabrication are sensitive to alignment factors, leading to inaccurate alignment checks, and require multiple marks for each exposure step, resulting in wasted wafer area and increased complexity.
Innovation Solution
A method to form an overlay mark using two exposure steps, specifically X-dipole and Y-dipole exposure steps, allowing all areas of the mark to be utilized for alignment checks, reducing the number of required overlay marks by 50% and enabling accurate alignment verification between layers defined by different exposure steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional overlay marks are used for alignment checks, then alignment accuracy can be verified, but the marks are too sensitive to certain factors other than alignment leading to inaccurate measurement
Solution Approach 1:
The overlay mark is divided into multiple distinct regions (first region with first linear patterns, second region with second linear patterns, third region with third linear patterns, fourth region with fourth linear patterns) where each region is defined by different exposure steps. This segmentation allows independent verification of alignment for each exposure step while reducing mutual interference and sensitivity to external factors.
2Measurement precision
If multiple overlay marks are formed for each exposure step, then alignment accuracy for each step can be checked, but the number of overlay marks increases and wafer area is wasted
Solution Approach 1:
Multiple overlay mark regions corresponding to different exposure steps are merged into a single integrated overlay mark structure. The first, second, third, and fourth linear pattern regions are all formed within one continuous mark structure, allowing alignment verification for multiple exposure steps simultaneously without requiring separate marks for each step.
Solution Approach 2:
The single overlay mark structure serves multiple functions by incorporating regions that can verify alignment for different exposure steps (first exposure step, second exposure step, and subsequent exposure steps). This multi-functional design eliminates the need for separate specialized marks for each exposure step.
3Measurement precision
If conventional overlay marks are used, then alignment can be checked, but the process complexity increases and wafer area is consumed
Solution Approach 1:
The overlay mark is segmented into distinct functional regions (first, second, third, fourth regions with different linear patterns) that correspond to different exposure steps. This segmentation allows each region to be optimized for its specific exposure step while maintaining overall structural integration, reducing the complexity that would arise from using multiple separate marks.
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 allows for precise alignment accuracy between layers defined by different exposure steps using a single overlay mark, optimizing wafer area utilization and simplifying the IC fabrication process.
Implementation Method 1
a first part and a second part of linear patterns of a mark are formed from a portion of a material layer and are respectively defined by two exposure steps that either belong to two lithography processes respectively or constitute a double-exposure process
Data Source
AI summary
A method of forming a mark in an IC fabricating process is described. Two parts of the mark each including a plurality of linear patterns are respectively defined by two exposure steps that either belong to two lithography processes respectively or constitute a double-exposure process including X-dipole and Y-dipole exposure steps.