Hybrid Micro-Bump RDL Structure for Lower Parasitic Capacitance
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Solution Overview
Problem
High-density integrated circuits face increased parasitic capacitance and RC delay due to densely packed metal lines, which limits conduction speed and is not effectively addressed by existing low-k dielectric materials in Inter-Layer and Inter-Metal Dielectric layers.
Innovation Solution
A hybrid bump integration scheme is introduced, allowing for the mixing of different conductive bumps (C4 bumps and micro-bumps) in the same region, along with the formation of dummy bumps over conductive lines, which eliminates the need for dummy conductive pads and enables more flexible design by using a dielectric layer to facilitate seed layer formation for bumps, improving manufacturing yield and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If low-k dielectric materials are employed in Inter-Layer and Inter-Metal Dielectric layers, then parasitic capacitance is reduced, but conduction speed is not sufficiently enhanced
Solution Approach 1:
The patent segments the bump structure into multiple functional layers (conductive bump, dielectric layer, seed layer, solder layer) to optimize different aspects of performance separately. The dielectric layer is specifically introduced between the conductive bump and substrate to address parasitic capacitance, while the segmented structure allows independent optimization of conduction pathways.
Solution Approach 2:
The dielectric layer acts as an intermediary element between the conductive bump and the substrate. This intermediary reduces the direct parasitic capacitance coupling while maintaining electrical connection through the seed layer, thereby reducing harmful capacitive effects without compromising conduction speed.
2Reliability
If dummy conductive pads are formed to accommodate bump placement, then manufacturing yield is improved, but device complexity increases
Solution Approach 1:
The patent uses dummy bumps as simplified copies or placeholders that replicate the structural form of functional bumps without requiring complex underlying conductive pad structures. These dummy bumps can be formed using the same bump formation process, simplifying manufacturing while maintaining yield.
Solution Approach 2:
The dielectric layer serves multiple functions: it reduces parasitic capacitance for functional bumps, provides a uniform formation surface for both dummy and functional bumps, and enables the same bump formation process to be used universally across the substrate regardless of whether underlying conductive pads are present.
3Adaptability or versatility
If hybrid bump integration is implemented, then design flexibility is improved, but manufacturing precision requirements increase
Solution Approach 1:
The dielectric layer with specific material properties (low-k dielectric constant) changes the electrical parameters of the bump structure, enabling different bump configurations (functional vs. dummy) to be formed with the same process parameters while achieving different electrical characteristics. This allows design flexibility without increasing precision requirements.
Data Source
AI summary
A semiconductor device includes a substrate; an interconnect structure over the substrate; a first passivation layer over the interconnect structure; a first conductive pad, a second conductive pad, and a conductive line disposed over the first passivation layer and electrically coupled to conductive features of the interconnect structure; a conformal second passivation layer over and extending along upper surfaces and sidewalls of the first conductive pad, the second conductive pad, and the conductive line; a first conductive bump and a second conductive bump over the first conductive pad and the second conductive pad, respectively, where the first conductive bump and the second conductive bump extend through the conformal second passivation layer and are electrically coupled to the first conductive pad and the second conductive pad, respectively; and a dummy bump over the conductive line, where the dummy bump is separated from the conductive line by the conformal second passivation layer.