Contact Pad Protrusions for Low-Resistance 3D Interconnects
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Solution Overview
Problem
Conventional methods for forming 3D metal interconnects in electronic devices face challenges in achieving high-quality, low-resistance contacts between interconnects and contact pads, especially as the aspect ratio of vias increases, making effective etching and metallization steps more difficult.
Innovation Solution
A method involving forming a front-side via in a substrate, depositing a contact pad material to fill the via, and then etching from the back side to expose protrusions, followed by depositing interconnect material that coats the back side and contacts the protrusions, facilitating low-resistance electrical coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the aspect ratio of vias increases to achieve higher I/O density and smaller package footprint, then device integration and functionality are improved, but the difficulty of etching and metallization steps increases
Solution Approach 1:
The contact pad protrusions are formed in advance before the interconnect vias are etched. This preliminary formation of protrusions ensures that when the vias are etched to high aspect ratios, the protrusions are already in position to receive the interconnect material, simplifying the metallization process despite the challenging via geometry
Solution Approach 2:
The contact pad protrusions act as an intermediary element between the substrate and the interconnects. These protrusions extend into the high aspect ratio vias and provide a surface for interconnect material deposition, mediating the connection between layers that would otherwise be difficult to form directly
2Device complexity
If conventional via-last approaches are used with deep via etching, then 3D integration is achieved, but low-resistance contact formation becomes more challenging
Solution Approach 1:
Instead of forming contacts after etching deep vias, the contact pad protrusions are formed beforehand. This preliminary action ensures that the protrusions are ready to receive interconnect material, guaranteeing low-resistance contact formation even when deep via etching is required for 3D integration
Solution Approach 2:
The conventional via-last approach is inverted to a via-first approach where contact pad protrusions are formed before the interconnect vias are etched. This inversion changes the sequence of operations to ensure reliable contact formation is established before the challenging deep via etching step
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 enables the formation of high-quality, low-resistance contacts between interconnects and contact pads, improving signal communication and reducing signal propagation delay, power consumption, and package footprint in 3D electronic devices.
Implementation Method 1
forming a contact pad comprising a protrusion, by depositing a contact pad material on the front side such that the contact pad material fills the front-side via
Implementation Method 2
forming an interconnect in contact with the contact pad by depositing an interconnect material which coats the back side surrounding the interconnect via, extends through a cross-section of the interconnect via, and contacts the frontside protrusion
Implementation Method 3
forming an interconnect via by etching the substrate from the back side until exposing the protrusion in the interconnect via
Data Source
AI summary
An electronic device includes a substrate including a front side, a back side, a thickness between the front side and back side, one or more front-side vias extending from the front side into a part of the thickness, and an interconnect via extending from the back side toward the front side; a contact pad on the front side and including one or more protrusions extending through corresponding front-side vias and into the interconnect via; and an interconnect extending through the interconnect via and into contact with the protrusion(s).