Semiconductor RDL Stack for High-Current Fine-Pitch Packaging
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Solution Overview
Problem
Existing semiconductor devices face challenges in handling large currents through redistribution wirings, leading to issues such as heat generation, electromigration, and disconnection, while also struggling with miniaturization due to pitch limitations and costly manufacturing processes for insulating films.
Innovation Solution
A semiconductor device structure featuring multiple layers of redistribution wirings and columnar electrodes, sealed with a non-photosensitive epoxy resin, allowing for large current flow and fine pitch arrangement, with manufacturing processes optimized to minimize cost and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the redistribution wiring is increased to handle large current (1-10 A), then the allowable current increases, but the pitch between wirings becomes narrower causing short-circuit faults during manufacturing
Solution Approach 1:
The patent transitions from a single-layer wiring structure to a multi-layer wiring structure. The first redistribution wiring is formed in a first opening, and a second redistribution wiring is formed in a second opening that overlaps with the first opening in the thickness direction. This vertical stacking allows current to be distributed across multiple layers, effectively increasing the total current capacity without requiring wider individual wirings or larger pitch between them in the planar direction.
Solution Approach 2:
The patent implements a nested structure where the second redistribution wiring is positioned within the projection area of the first redistribution wiring when viewed from the thickness direction. The openings are arranged such that the second opening overlaps with the first opening, creating a nested configuration that maximizes space utilization and allows fine pitch arrangement while maintaining adequate current carrying capacity through the multi-layer structure.
2Reliability
If the pitch between redistribution wirings is widened to increase allowable current, then heat generation and electromigration are reduced, but the region for forming necessary redistribution wirings becomes insufficient
Solution Approach 1:
By utilizing the thickness dimension to create multiple wiring layers, the patent allows current to be distributed vertically across layers. This enables the use of narrower pitch between wirings in the planar direction while still achieving adequate current capacity and heat dissipation through the multi-layer configuration, thus preserving the available area for forming necessary redistribution wirings.
Solution Approach 2:
The patent segments the current path into multiple parallel paths by creating multiple redistribution wirings in different layers. The first and second redistribution wirings are electrically connected to pad electrodes and form separate current-carrying paths that can be optimized independently, allowing better current distribution and heat management without requiring excessive pitch between individual wirings.
3Manufacturing precision
If photosensitive polyimide is used as insulating film for thick redistribution wiring, then a large step difference occurs on the surface, but it becomes difficult to completely cover the redistribution wiring layer
Solution Approach 1:
The patent forms insulating films and openings in a multi-layer structure where the second insulating film is formed over the first insulating film and the side surface of the first redistribution wiring. By creating overlapping openings in different layers, the structure accommodates the step differences caused by thick wirings while ensuring complete coverage and electrical isolation through the stacked insulating film configuration.
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 enables efficient large current handling, prevents heat and disconnection issues, facilitates miniaturization, and reduces manufacturing costs by using a non-photosensitive resin and simplified processing techniques.
Implementation Method 1
The redistribution wiring is made of a material mainly consisting of copper and is formed by, for example, the plating method in order to reduce the wiring resistance
Implementation Method 2
by an electroplating method, a columnar electrode is formed on the redistribution wiring
Data Source
AI summary
A semiconductor wafer has a first pad electrode and a plurality of second pad electrodes formed on an upper surface thereof. A first opening and a plurality of second openings are formed in an insulating film covering the first pad electrode and the plurality of second pad electrodes. The first pad electrode is electrically connected to a first redistribution wiring in the first opening, and the plurality of second pad electrodes are electrically connected to a second redistribution wiring in the plurality of second openings. The first redistribution wiring has a narrow region and a wide region, a first columnar electrode is formed on the wide region, and a second columnar electrode is formed on the first columnar electrode. A third redistribution wiring is formed on the second redistribution wiring, and a plurality of third columnar electrodes are formed on the third redistribution wiring.