Mechanically Anchored C4 Pad for Flip Chip Reliability
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Solution Overview
Problem
Conventional controlled collapse chip connection (C4) pads in flip chip technology are prone to delamination and separation due to thermal expansion differences and mechanical stresses, leading to reliability issues in electrical connections.
Innovation Solution
A method and structure that involves forming a through substrate via (TSV) with a mechanically anchored bonding pad, where a diffusion barrier is used to prevent material diffusion and an anchor region is created to securely engage the bonding pad with the semiconductor substrate, ensuring direct electrical contact and preventing physical separation from the TSV.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional C4 pads are used without mechanical anchoring, then the fabrication process is simpler, but the bonding pad delaminates and separates due to thermal expansion differences and mechanical stresses
Solution Approach 1:
The patent applies preliminary action by forming the anchor trench and depositing the diffusion barrier material before forming the bonding pad. This preparatory anchoring structure is created in advance to prevent delamination and separation that would occur during subsequent thermal cycling and mechanical stress, thereby improving reliability without adding complex post-processing steps
Solution Approach 2:
The bonding pad structure is segmented into distinct functional regions: the anchor region with the anchor trench for mechanical attachment, the diffusion barrier layer for material containment, and the bonding pad region for electrical connection. This segmentation allows each component to perform its specific function optimally, preventing delamination while maintaining fabrication feasibility
2Reliability
If no diffusion barrier is used, then the fabrication process is simpler and faster, but the conductive material diffuses into the semiconductor substrate causing electrical failures
Solution Approach 1:
The diffusion barrier layer acts as an intermediary between the bonding pad conductive material and the semiconductor substrate. This intermediate layer prevents direct diffusion of conductive material into the substrate while maintaining electrical connectivity through the anchor region, thereby ensuring electrical connection stability without significantly complicating the fabrication process
Solution Approach 2:
The diffusion barrier is applied locally within the anchor trench and at the bonding pad-substrate interface where diffusion risk exists. This localized application provides protection exactly where needed without requiring blanket coverage, maintaining fabrication simplicity while ensuring electrical connection reliability
3Reliability
If the bonding pad is not mechanically anchored, then the fabrication process requires fewer steps, but the bonding pad separates from the TSV during temperature fluctuations
Solution Approach 1:
The anchor trench structure嵌套 (nests) the bonding pad attachment region within the semiconductor substrate. The diffusion barrier is nested within the anchor trench, and the conductive material is nested within the diffusion barrier structure. This nested configuration provides mechanical anchoring that prevents separation during thermal cycling without adding significant structural complexity
Solution Approach 2:
The patent transitions from a two-dimensional bonding pad surface to a three-dimensional anchored structure by creating the anchor trench that extends vertically into the substrate. This dimensional change provides mechanical interlocking that prevents delamination while maintaining a compact overall structure that does not significantly increase device complexity
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 solution provides a durable and robust connection that reduces delamination and separation of the bonding pad from the semiconductor wafer and TSV during temperature fluctuations, enhancing the reliability and stability of electrical connections.
Implementation Method 1
forming a diffusion barrier on the back side of the semiconductor substrate and within the anchor trench
Implementation Method 2
depositing a conductive material on the diffusion barrier and within the anchor trench to form a bonding pad comprising an anchor region, so that the conductive material is in direct electrical contact with the bottom surface of the TSV
Data Source
AI summary
The present invention relates generally to flip chip technology and more particularly, to a method and structure for fabricating a mechanically anchored controlled collapse chip connection (C4) pad on a semiconductor structure. In an embodiment, a method is disclosed that may include forming a bonding pad having one or more anchor regions that extend into a semiconductor structure and may inhibit the bonding pad from physically separating from the TSV during temperature fluctuations.