Mechanically Anchored C4 Pad Groove Patterning
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Solution Overview
Problem
The existing flip chip technology faces issues with delamination and separation of bonding pads from semiconductor wafers and TSVs due to thermal expansion differences and mechanical stresses, leading to reliability problems in electrical connections.
Innovation Solution
A method for fabricating a mechanically anchored controlled collapse chip connection (C4) pad using a self-assembling block copolymer layer to create a pattern of grooves, which serves as a mask for patterning the dielectric and semiconductor substrates, allowing for direct electrical contact and anchoring of the C4 pad with the via, thereby reducing delamination risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flat interface is formed between the semiconductor wafer/TSV and the bonding pad, then a continuous electrical connection is provided, but delamination and separation occur during thermal fluctuations
Solution Approach 1:
The invention replaces the conventional flat interface between the bonding pad and semiconductor substrate with a curved surface. The bonding pad is formed with a domed or convex upper surface that contacts the solder bump, and the lower surface of the bonding pad follows the curvature of the TSV, creating a curved interface that increases contact area and mechanical anchoring, thereby preventing delamination during thermal cycling while maintaining electrical continuity.
Solution Approach 2:
The invention transitions from a two-dimensional flat interface to a three-dimensional curved interface by forming the bonding pad surface to conform to the curvature of the TSV. This dimensional change allows the bonding pad to wrap around the TSV, creating multiple contact points and increasing the effective bonding area, which enhances both mechanical attachment and electrical connection reliability under thermal stress.
2Reliability
If the bonding pad is formed by depositing conductive material over the back side of the semiconductor wafer, then electrical connection is established, but the bonding pad separates from the semiconductor wafer and TSV due to thermal expansion differences
Solution Approach 1:
The invention changes the geometric parameters of the bonding pad structure by forming it with a curved surface that matches the TSV curvature, rather than a flat surface. This parameter change increases the contact area and distribution of mechanical stress, allowing the bonding pad to better accommodate thermal expansion differences between materials while maintaining strong attachment and continuous electrical connection.
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
The mechanically anchored C4 pad effectively inhibits delamination during thermal fluctuations, maintaining reliable electrical contact and improving the structural integrity of flip chip connections.
Implementation Method 1
forming a self-assembling block copolymer (BCP) layer on the dielectric layer and the surface of the via, the self-assembling BCP layer having a pattern of grooves therein
Implementation Method 2
forming a controlled collapse chip connection (C4) pad by depositing a conductive material on the patterned dielectric layer and within the grooves of the patterned dielectric layer
Data Source
AI summary
The present disclosure relates generally to flip chip technology and more particularly, to a method for fabricating a mechanically anchored controlled collapse chip connection (C4) pad on a semiconductor structure and a structure formed thereby. In an embodiment, a method is disclosed that includes forming a C4 pad on a patterned dielectric layer having grooves therein, the grooves providing an interfacial surface area between the patterned dielectric layer and the C4 pad sufficient to inhibit the C4 pad from delaminating during thermal expansion or contraction.