Honeycomb Photomask Layout for Polygonal Die Exposure Alignment
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Solution Overview
Problem
Conventional stepper exposure equipment experiences alignment errors between adjacent field areas on wafers with polygonal dies, leading to incomplete exposure and reduced utilization rates.
Innovation Solution
A wafer exposure layout method involving parallel linear exposure paths with partially overlapping rectangular field areas and a photomask with a honeycomb structure of regular hexagonal units, ensuring precise alignment and complete exposure through step-and-repeat movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a rectangular photomask is used to expose polygonal dies on a wafer, then the exposure process can be performed on multiple field areas, but alignment errors occur between adjacent field areas causing incomplete exposure
Solution Approach 1:
The photomask is divided into multiple completely regular hexagonal units arranged in a honeycomb structure, where each hexagonal unit corresponds to one polygonal die. This segmentation allows each unit to be precisely aligned with its corresponding die while maintaining overall photomask integrity, eliminating alignment errors between adjacent field areas.
Solution Approach 2:
The photomask transitions from a symmetric rectangular structure to an asymmetric honeycomb structure composed of regular hexagonal units. This asymmetric design matches the polygonal die geometry, enabling precise alignment between the photomask edges and die boundaries, thereby preventing exposure gaps and improving manufacturing precision.
2Productivity
If rectangular field areas are used for exposure, then the photomask can cover multiple dies, but exposure gaps occur between adjacent field areas reducing wafer utilization
Solution Approach 1:
The photomask is segmented into multiple completely regular hexagonal units that form a honeycomb structure. Each hexagonal unit precisely matches the geometry of a polygonal die, ensuring complete coverage without gaps. This segmentation allows the photomask to adapt to the specific geometry of each die while maintaining continuous exposure coverage across the wafer surface.
Solution Approach 2:
The photomask employs different geometric characteristics at different locations: each local hexagonal unit is optimized to match its corresponding polygonal die geometry, while the overall honeycomb structure provides global coverage. This local quality approach ensures that each die receives complete exposure while maximizing wafer utilization across the entire wafer surface.
Data Source
AI summary
A wafer exposure layout method includes planning a plurality of linear exposure paths for the wafer. Each linear exposure path includes a plurality of rectangular exposure field areas arranged side by side along a straight line, and any rectangular exposure field area partially overlaps another adjacent rectangular exposure field area. Then a photomask with a honeycomb structure composed of a plurality of completely regular hexagonal units is provided. The photomask moves one by one along the plurality of linear exposure paths, and when the photomask moves along any linear exposure path, the photomask is moved one by one along the plurality of rectangular exposure field areas. A side of the photomask that moves to a first exposure position in any rectangular exposure field area is partially embedded with an opposite side of the photomask that moves to a second exposure position in another adjacent rectangular exposure field area.