Redistribution Layer Overhang Removal via Etching
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Solution Overview
Problem
Conventional flip chip package technology results in poor coverage of redistribution layers over via holes, leading to void formation and pinhole failures in semiconductor devices due to overhang structures, which compromises the reliability and yield of the manufacturing process.
Innovation Solution
A method is introduced where an etching process is used to pattern the redistribution layer and remove the overhang structure, forming V-shaped or U-shaped cavities above the via holes, ensuring better coverage by the subsequent passivation layer and preventing void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the redistribution layer is deposited to cover the via hole, then the via hole is covered, but an overhang structure is formed above the via hole due to poor coverage
Solution Approach 1:
The patent applies preliminary action by forming a mandrel structure before depositing the redistribution layer. The mandrel is positioned within the via hole to provide a foundation that guides the redistribution layer deposition, ensuring the layer conforms to the via hole shape and prevents overhang formation from the start
2Reliability
If a passivation layer is deposited to cover the redistribution layer, then the redistribution layer is protected, but voids are formed in the passivation layer under the overhang structure
Solution Approach 1:
The mandrel structure is formed in advance to prevent the overhang problem before it occurs. By having the mandrel in place during redistribution layer deposition, the layer naturally follows the via hole contour, eliminating the overhang that would otherwise cause voids in the subsequent passivation layer
Solution Approach 2:
The mandrel acts as an intermediary structure between the via hole and the redistribution layer. It provides a physical guide that ensures the redistribution layer conforms to the desired shape, preventing both overhang formation and subsequent void creation in the passivation layer
3Ease of manufacture
If the redistribution layer has poor coverage, then deposition is simpler, but pinhole failures occur in the semiconductor device
Solution Approach 1:
The mandrel is formed before redistribution layer deposition to guide the layer into proper coverage of the via hole. This preliminary structure ensures complete coverage without requiring complex deposition techniques, maintaining ease of manufacture while preventing pinhole failures
Solution Approach 2:
The mandrel serves as a mediator that translates the simple deposition process into high-quality coverage. It allows the redistribution layer to be deposited uniformly while ensuring it conforms to the via hole shape, achieving both ease of manufacture and reliability
Data Source
AI summary
In a method for manufacturing a semiconductor device, a semiconductor substrate having a top surface is provided. A top metal layer is formed in the top surface. A first passivation layer is formed to cover the top metal layer and the top surface. The first passivation layer has a via hole exposing a portion of the top metal layer. A redistribution layer is formed to cover the first passivation layer, the portion of the top metal layer, and a side surface of the via hole. The redistribution layer includes an overhang structure over the via hole. An etching process is performed on the redistribution layer to remove the overhang structure and a portion of the redistribution layer to expose a portion of the first passivation layer. A second passivation layer is formed to cover the redistribution layer and the portion of the first passivation layer.