Metal Rings in Semiconductor Device Dies
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Solution Overview
Problem
The packaging process of semiconductor chips faces challenges in maintaining mechanical strength and preventing delamination and moisture penetration during the sawing of wafers into device dies, especially with the increasing complexity of Package-on-Package technology.
Innovation Solution
The formation of metal rings around the edges of device dies, which are electrically coupled to metal pillars and passivation layers, enhances mechanical strength and resistance to moisture penetration by providing additional structural support and insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the wafer structure is simplified without metal rings, then the manufacturing process is easier and device complexity is reduced, but the mechanical strength decreases and delamination and moisture penetration occur during sawing
Solution Approach 1:
Metal rings are formed around the periphery of the wafer before the sawing process. This preliminary structural reinforcement prevents delamination and moisture penetration during subsequent processing steps, resolving the contradiction by providing mechanical strength in advance without complicating the core device structure.
Solution Approach 2:
The wafer structure is segmented into functional regions: a central active area containing device components and a peripheral region containing metal rings. This segmentation allows the metal rings to provide mechanical support without interfering with the device functionality, thus maintaining simplicity while enhancing strength.
2Reliability
If metal rings are added around device die edges, then resistance to moisture penetration and delamination is improved, but manufacturing complexity and process steps increase
Solution Approach 1:
The metal rings are formed using the same semiconductor fabrication processes already employed for creating interconnect structures, such as sputtering or electroplating. By merging the metal ring formation into existing manufacturing workflows, the process adds reliability without significantly increasing manufacturing complexity.
Solution Approach 2:
The metal rings serve multiple functions: providing mechanical strength during sawing, preventing delamination, and blocking moisture penetration. This multi-functionality justifies the additional process step by delivering multiple reliability benefits from a single structural addition.
Data Source
AI summary
A die includes a metal pad, a passivation layer over the metal pad, and a polymer layer over the passivation layer. A metal pillar is over and electrically coupled to the metal pad. A metal ring is coplanar with the metal pillar. The polymer layer includes a portion coplanar with the metal pillar and the metal ring.