Semiconductor Pad Structure with Ring Metal Film
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Solution Overview
Problem
Existing semiconductor device pad structures face issues such as increased chip size due to thick topmost layer metal films, difficulty in reducing metal film wiring width, and larger parasitic resistance, which can lead to disconnection and increased chip size.
Innovation Solution
A semiconductor device with a pad structure featuring a metal film with a rectangular donut shape protruding into the pad opening, an insulating film, a topmost layer metal film, and a protective film with a via for electrical connection, where the metal film is absent under the beveled corner of the capillary, increasing the effective thickness of the insulating film and reducing parasitic resistance without enlarging the pad structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick topmost layer metal film is formed to increase strength against bonding, then crack resistance is improved, but the wiring width cannot be sufficiently reduced and chip size increases
Solution Approach 1:
The invention applies different metal film thicknesses to different locations: a thick topmost layer metal film is formed only in the pad opening area where bonding occurs to provide crack resistance, while the metal film wiring areas maintain a thinner profile to enable sufficient width reduction. This local differentiation resolves the contradiction by concentrating strength where needed without sacrificing wiring compactness elsewhere.
2Reliability
If the distance from pad opening edge to metal film edge is increased to reduce parasitic resistance, then electrical characteristics are improved, but pad structure size increases
Solution Approach 1:
The invention creates a local expansion of the metal film area within the pad opening boundaries, forming a rectangular donut shape that extends toward the center. This local area increase provides additional conduction paths and reduces parasitic resistance without expanding the overall pad structure footprint, thus maintaining compact chip size while improving electrical characteristics.
3Reliability
If a thick insulating film is formed under the pad opening to absorb bonding damage, then crack development is inhibited, but manufacturing complexity increases
Solution Approach 1:
The invention segments the insulating film structure into multiple layers with different functions: a first insulating film layer provides the primary thick cushioning layer under the pad opening to absorb bonding damage, while a second insulating film layer provides additional insulation and structural support. This segmentation allows the thick insulating film to be integrated into the existing multi-layer fabrication process without requiring entirely new manufacturing steps.
Data Source
AI summary
In order to inhibit forming cracks under a pad opening during ball bonding without increasing a chip size, a protective film includes a pad opening that exposes a part of a topmost layer metal film of the chip. A second metal film provided under the pad opening has a ring shape that defines a rectangular opening under the pad opening. The opening edge of the opening in the second metal film extends inwardly beyond the edge of the overlying pad opening. Vias connect the second metal film and the topmost layer metal film, and all of these vias are located outside the pad opening in plan view.