Redistribution Line Stitching for Fine and Coarse Lithography
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Solution Overview
Problem
The integration of more functions in integrated circuit packages leads to larger interposers, causing challenges in the formation of efficient redistribution lines due to the difficulty in forming fine and coarse lines with existing lithography processes.
Innovation Solution
A method involving two photolithography masks is used to form redistribution lines, where a first mask forms coarse lines and a second mask forms fine lines, with a stitching process to connect them, reducing the need for multiple exposure processes and masks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single photolithography mask is used to form redistribution lines, then the process is simple, but it is impossible to form both fine and coarse lines with different widths
Solution Approach 1:
The patent divides the redistribution line formation into two separate photolithography processes: one for forming fine lines and another for forming coarse lines. This segmentation allows each mask to be optimized for its specific line width requirements, achieving precise control over different line widths while maintaining process simplicity through modular fabrication steps.
2Manufacturing precision
If multiple photolithography masks are used to form fine and coarse lines separately, then both line types can be formed, but the process complexity and number of steps increase
Solution Approach 1:
The patent employs preliminary action by forming fine redistribution lines first, then using them as a reference guide for subsequent coarse line formation. The fine lines are established in advance to define the routing paths, and the coarse lines are later added along the same paths. This preliminary establishment of fine lines simplifies the overall process by providing a template for coarse line placement, reducing the need for complex alignment procedures and multiple iterative steps.
3Adaptability or versatility
If the interposer size is increased to integrate more functions, then more routing is needed, but existing lithography processes cannot efficiently form both fine and coarse lines
Solution Approach 1:
The patent applies local quality by using different line widths (fine and coarse) in different regions of the interposer based on local routing requirements. Fine lines are used in regions requiring high density and precision, while coarse lines are used in regions requiring higher current carrying capacity or easier manufacturability. This localized optimization allows the interposer to accommodate diverse routing needs across different functional areas without requiring a single complex lithography process.
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 simplifies the formation of redistribution lines by using two masks, allowing for both fine and coarse lines to be efficiently created, meeting routing requirements while reducing the complexity of the process.
Implementation Method 1
forming a photoresist, and light-exposing the photoresist through a first light-exposure process and a second light-exposure process
Data Source
AI summary
A method includes forming a photoresist on a base structure, and performing a first light-exposure process on the photoresist using a first lithography mask. In the first light-exposure process, an inner portion of the photoresist is blocked from being exposed, and a peripheral portion of the photoresist is exposed. The peripheral portion encircles the inner portion. A second light-exposure process is performed on the photoresist using a second lithography mask. In the second light-exposure process, the inner portion of the photoresist is exposed, and the peripheral portion of the photoresist is blocked from being exposed. The photoresist is then developed.