Redistribution Layer Fabrication Using Inverted Sacrificial Mask
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Solution Overview
Problem
Conventional methods for forming redistribution layers (RDL) in semiconductor packaging face challenges such as undercutting and incomplete etching, leading to electrical leakage and difficulty in achieving uniform critical dimensions due to small pitch requirements and limitations in lithography resolution.
Innovation Solution
A manufacturing method involving a patterned sacrificial layer with an actuate angle between its side wall and carrier, allowing for the formation of a conductive layer with specific portions on the carrier and sacrificial layer, which is then removed to avoid undercutting and enable fine pitch RDL formation without additional etching, ensuring improved uniformity of critical dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photolithography and etching processes are used to form RDL, then the process is simple and well-established, but undercutting occurs and critical dimension uniformity deteriorates
Solution Approach 1:
The patent applies preliminary action by forming a sacrificial layer with a specific inverted trapezoid profile before depositing the conductive layer. The actuate angle (80-88 degrees) is pre-designed to prevent the conductive material from conformally coating the side walls, thereby preventing undercut formation before the etching process even begins. This preliminary structural design resolves the undercutting issue inherent in conventional approaches.
Solution Approach 2:
The patent inverts the traditional approach by using a sacrificial layer with an inverted trapezoid cross-section where the top width is greater than the bottom width. This inverted geometry creates the actuate angle that actively prevents conductive material from adhering to side walls during deposition, thereby preventing undercutting rather than trying to correct it after formation.
2Length of moving object
If smaller pitch RDL is formed to meet finer interconnection requirements, then the interconnection density improves, but the critical dimension becomes too small to etch completely, causing electrical leakage
Solution Approach 1:
The sacrificial layer is pre-formed with an inverted trapezoid profile and actuate angle designed to prevent conductive material from coating the side walls. This preliminary geometric design ensures that even at 4-10 μm pitch, the conductive layer forms only on the carrier surface, creating natural gaps that prevent electrical leakage while maintaining fine pitch dimensions.
Solution Approach 2:
The sacrificial layer acts as an intermediary structure that defines the final RDL pattern. By removing the sacrificial layer after conductive layer formation, the patent creates precisely controlled gaps between conductive features without requiring direct etching of the conductive material itself, thereby preventing leakage at fine pitches.
3Manufacturing precision
If additional etching processes are performed to achieve precise RDL profiles, then the manufacturing precision improves, but the process complexity and cost increase
Solution Approach 1:
The inverted trapezoid sacrificial layer with actuate angle is pre-formed to actively prevent conductive material from coating side walls during deposition. This preliminary geometric design eliminates the need for subsequent etching processes to achieve precise RDL profiles, as the desired profile is self-formed during the deposition step itself, thereby reducing process complexity while maintaining precision.
Solution Approach 2:
The sacrificial layer structure self-services by its own geometry (inverted trapezoid with actuate angle) to prevent unwanted conductive material deposition on side walls. This self-limiting geometric design eliminates the need for additional etching processes to correct profile errors, as the correct profile is achieved automatically during deposition without requiring further process steps.
Data Source
AI summary
A manufacturing method of a redistribution layer is provided. The method includes the following steps. A patterned sacrificial layer is formed on a carrier. An actuate angle is formed between a side wall of the patterned sacrificial layer and the carrier. A first conductive layer is formed. The first conductive layer includes a plurality of first portions formed on the carrier and a plurality of second portions formed on the patterned sacrificial layer. The patterned sacrificial layer and the second portions of the first conductive layer are removed from the carrier. Another manufacturing method of a redistribution layer is also provided.