Circular Overlay Mark for Wafer Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional overlay marks fail to accurately measure overlay errors in wafers undergoing hole-opening processes due to uneven conductive material filling, leading to faults and cracks, especially in thicker wafers, making it impossible to design rectangular openings for alignment.
Innovation Solution
The introduction of a circular overlay mark with sub-marks on the first layer and a center-symmetrical linear graphic overlay mark on the second layer, allowing for accurate measurement of overlay errors during the hole-opening process by preventing conductive material faults and extending the measurement capability to wafers with thicknesses greater than 10 μm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rectangular alignment mark is used for overlay measurement, then the measurement capability is sufficient for conventional processes, but the conductive material filling becomes uneven in hole-opening processes leading to faults and cracks
Solution Approach 1:
The patent changes the alignment mark shape from rectangular to circular. The circular shape eliminates corners where conductive material tends to accumulate or fail to fill properly. The curved geometry ensures uniform material distribution during the hole-opening process, preventing faults and cracks while maintaining measurement capability.
2Strength
If the wafer thickness is increased beyond 10 μm to meet certain requirements, then the structural integrity is improved, but the overlay error measurement accuracy deteriorates due to conventional alignment mark limitations
Solution Approach 1:
The circular alignment mark design works effectively with thicker wafers (>10 μm) because the curved geometry maintains consistent optical reflection and imaging properties regardless of wafer thickness. The circular shape provides stable measurement references that are not affected by the increased thickness, unlike rectangular marks which suffer from corner-related measurement errors.
3Adaptability or versatility
If a normal pattern is designed for overlay measurement, then the measurement process is straightforward, but it becomes impossible to measure overlay error in layers requiring hole-opening processes
Solution Approach 1:
The circular alignment mark serves as a universal measurement structure that works across different process types including hole-opening processes. The design integrates the measurement function with the hole-opening structure itself, making the alignment mark applicable to both conventional and specialized processes without requiring separate measurement structures.
Data Source
AI summary
The present disclosure provides an overlay mark, an overlay error measurement method for a wafer, and a wafer stacking method. The overlay mark includes a first overlay mark disposed on a first layer, and a second overlay mark disposed on a second layer. The first layer and the second layer are stacked. The first overlay mark includes at least one first overlay sub-mark, and each of the at least one first overlay sub-mark is circular in shape. The second overlay mark includes a second overlay sub-mark, and the second overlay sub-mark is in a center-symmetrical shape including a plurality of linear graphics.