Chamfered Seal Ring Design for IC Packaging

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Solution Overview

Problem

Conventional seal ring designs in integrated circuits (ICs) lead to defects during packaging due to resist bubbles forming at corners, causing under-bump issues due to poor seed layer coverage.

Innovation Solution

An improved seal ring design featuring an inner moisture oxygen barrier (MOB) ring and an outer crack stop (CS) ring with chamfered corners, both devoid of acute angles, integrated into the back-end-of-line (BEOL) dielectric structure to minimize moisture absorption and crack propagation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional seal ring designs with acute angle corners are used, then the seal ring provides basic moisture and crack protection, but resist bubbles form at corners causing packaging defects

Engineering Contradiction:

Improvepackaging reliabilityVSAvoidresist bubbles at corners

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies curvature by replacing acute angle corners with chamfered corners (45-degree angled corners) in the seal ring structure. This geometric modification eliminates the sharp corners that trap resist material during photolithography, preventing resist bubble formation while maintaining the seal ring's protective function against moisture and cracks.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Ease of manufacture

If conventional seal ring designs are used, then the structure is simple to manufacture, but poor seed layer coverage occurs due to resist bubbles

Engineering Contradiction:

Improveseal ring fabricationVSAvoidseed layer coverage

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The chamfered corner design maintains manufacturing simplicity while significantly improving seed layer coverage. The 45-degree chamfer geometry is easily implemented in standard photolithography and etching processes, eliminating resist bubbles that would otherwise prevent proper seed layer deposition and subsequent metal filling.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Device complexity

If acute angle corners are used in seal ring, then the design is straightforward, but cracks can propagate into the IC during dicing

Engineering Contradiction:

Improveseal ring designVSAvoidcrack resistance

Core Design Contradiction:

Device complexityVSStrength

Solution Approach 1:

The chamfered corner design adds minimal geometric complexity while dramatically improving crack resistance. The angled corners act as stress distributors that prevent crack initiation and propagation during the dicing process, protecting the IC from saw-induced cracks without requiring complex multi-layer or curved structures.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentUS10121755B1Robust chamfer design for seal ring

Publication Date: 2018.11.06 GLOBALFOUNDRIES SINGAPORE PTE LTD

AI summary

A seal ring structure is disclosed for integrated circuit (IC) packaging. The seal ring includes an inner moisture barrier ring and an outer crack stop ring. Line structures of both the inner and outer rings include chamfered corners. The chamfers of a chamfered corner are devoid of acute angles. No metal line structure for the inner ring is provided at the pad level. The seal ring as described improves the reliability and strength of the structure and hence the seal ring can sustain high stress at the corners of the die during dicing.