Narrow Trace Redistribution Layer with Segmented Passivation
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Solution Overview
Problem
Conventional semiconductor package design faces challenges in creating fine pitch redistribution layers due to complex patterning and time-consuming processes, particularly in small areas, which complicates the design and increases the risk of electric shorts and reduces design freedom.
Innovation Solution
A semiconductor device with fine pitch redistribution layers is designed, featuring a redistribution layer (RDL) with a uniform width, an under bump metal (UBM) with a larger area than the connection region, and a passivation layer configuration that simplifies the manufacturing process by eliminating the need for a pad connection between the RDL and UBM, allowing for easier design and reduced risk of electric shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the RDL width is reduced to achieve fine pitch, then the area occupied by the RDL is reduced, but the patterning complexity and manufacturing difficulty increase significantly
Solution Approach 1:
The passivation layer is segmented into multiple regions with different opening sizes: a first opening for the bond pad and a second opening for the RDL connection region. This segmentation allows the RDL to be formed with a narrow width while the passivation layer opening remains larger, reducing patterning complexity for the RDL itself while maintaining proper electrical connections.
2Adaptability or versatility
If the RDL width is reduced to increase design freedom, then more space is available for other components, but the risk of electric shorts increases
Solution Approach 1:
The passivation layer is designed with different opening sizes at different locations: a larger first opening for the bond pad area and a second opening for the RDL connection region. This local quality differentiation ensures that the RDL connection region has sufficient opening area for reliable electrical connection while the RDL trace itself maintains a narrow width for design freedom, thereby reducing short circuit risk through proper spatial differentiation of functions.
3Productivity
If the RDL width is reduced to simplify the manufacturing process, then fewer patterning steps are needed, but the connection reliability between RDL and UBM deteriorates
Solution Approach 1:
The solution addresses the connection reliability issue by expanding in the vertical dimension through the passivation layer opening rather than increasing the RDL horizontal width. The second opening in the passivation layer provides a larger vertical access area for the RDL to connect to the UBM, allowing the RDL trace width to remain narrow while maintaining reliable electrical connection through the enlarged opening dimension.
Data Source
AI summary
A semiconductor device with fine pitch redistribution layers is disclosed and may include a semiconductor die with a bond pad and a first passivation layer comprising an opening above the bond pad. A redistribution layer (RDL) may be formed on the passivation layer with one end of the RDL electrically coupled to the bond pad and a second end comprising a connection region. A second passivation layer may be formed on the RDL with an opening for the connection region of the RDL. An under bump metal (UBM) may be formed on the connection region of the RDL and a portion of the second passivation layer. A bump contact may be formed on the UBM, wherein a width of the RDL is less than a width of the opening in the second passivation layer and may be constant from the bond pad through at least a portion of the opening.