Electrical Interconnection Structure to Prevent Seed-Layer Undercut
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Solution Overview
Problem
In 3D IC chip stacking technologies, the etching of the seed layer during silicon interposer fabrication often results in an undercut structure, leading to adhesive residual issues that compromise the bonding between conductive pads and conductive bumps, reducing the electrical interconnection quality and reliability of semiconductor packages.
Innovation Solution
A substrate with a specific electrical interconnection structure is developed, featuring a first metal layer embedded within passivation layers and a second metal layer protruding from them, where the first metal layer is not protruded from the passivation layers to prevent undercut formation during etching, and a seed layer is used between the metal layers and conductive pads to facilitate etching without eroding the metal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the seed layer is etched during silicon interposer fabrication, then the metal portions can be electrically connected to the conductive pads, but an undercut structure is formed that causes adhesive residual issues and reduces bonding quality
Solution Approach 1:
The patent applies preliminary action by forming the metal layer with a protruding portion that extends beyond the passivation layer before the etching process. This protruding structure is intentionally created in advance to serve as a protective barrier during subsequent etching operations, preventing the formation of undercut structures that would compromise bonding quality.
Solution Approach 2:
The patent implements preliminary anti-action by designing the metal layer protruding portion to counteract the harmful effect of etching. The protruding metal structure acts as a protective barrier that prevents the etchant from creating undercut formations, thereby eliminating the root cause of adhesive residual issues and bonding defects.
2Manufacturing precision
If the metal layer is formed to protrude from the passivation layer, then bonding quality is improved, but the device complexity increases
Solution Approach 1:
The patent applies local quality by creating a metal layer with non-uniform geometry - specifically, a protruding portion that extends beyond the passivation layer only in the regions where enhanced bonding is required. This localized structural modification provides improved bonding quality at critical interfaces while maintaining a relatively simple overall device architecture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach prevents undercut structures from forming, ensuring better bonding between conductive pads and bumps, enhancing the electrical interconnection quality and reliability of semiconductor packages by eliminating adhesive residuals and improving product yield.
Implementation Method 1
a seed layer is used between the metal layers and conductive pads to facilitate etching without eroding the metal layers
Data Source
AI summary
A method for fabricating a substrate having an electrical interconnection structure is provided, which includes the steps of: providing a substrate body having a plurality of conductive pads and first and second passivation layers sequentially formed on the substrate body and exposing the conductive pads; forming a seed layer on the second passivation layer and the conductive pads; forming a first metal layer on each of the conductive pads, wherein the first metal layer is embedded in the first and second passivation layers without being protruded from the second passivation layer; and forming on the first metal layer a second metal layer protruded from the second passivation layer. As such, when the seed layer on the second passivation layer is removed by etching using an etchant, the etchant will not erode the first metal layer, thereby preventing an undercut structure from being formed underneath the second metal layer.