UBM-Free Metal Skeleton Frame With Support Studs for IC Packaging
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Solution Overview
Problem
Conventional substrate-less integrated circuit (IC) packages require separate fabrication steps for under-bump metallization (UBM) structures, increasing device fabrication time, effort, and cost.
Innovation Solution
An IC package design that utilizes a UBM-free metal skeleton structure with support studs, where package bumps are directly connected to redistribution layer (RDL) traces without intervening UBM, and a metallization-first process that eliminates multiple fabrication steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional UBM structure is formed over the RDL to provide robust mechanical and electrical connection, then the connection reliability is improved, but the fabrication time and process complexity increase due to requiring separate fabrication steps
Solution Approach 1:
The patent merges the UBM formation step with the RDL formation step into a single fabrication process. The metal skeleton structure is formed concurrently with the RDL trace, eliminating the need for separate UBM fabrication steps while maintaining the robust mechanical and electrical connection between the package bump and the RDL
2Object-affected harmful factors
If a conventional UBM structure is formed over the RDL to mitigate unwanted diffusion, then the diffusion protection is improved, but the manufacturing complexity increases due to additional process steps
Solution Approach 1:
The patent combines the diffusion barrier function with the RDL trace itself. The metal skeleton structure serves dual purposes: as the electrical connection path and as the diffusion barrier, eliminating the need for separate UBM layers while still protecting against unwanted diffusion between the package bump and the RDL
Solution Approach 2:
The metal skeleton structure performs multiple functions simultaneously: it provides mechanical support, electrical connection, and diffusion protection. This multi-functional design eliminates the need for dedicated UBM structures while maintaining all necessary protective and connective functions
3Strength
If separate fabrication steps are used for UBM formation, then the connection robustness is improved, but the manufacturing cost increases
Solution Approach 1:
The patent combines multiple fabrication operations into a single process step. The metal skeleton structure is formed in the same fabrication step as the RDL trace, using a single photo-resist pattern and metal deposition process, thereby reducing manufacturing cost while maintaining connection robustness
4Productivity
If a UBM-free metal skeleton structure is used to reduce fabrication steps, then the fabrication time and cost are reduced, but the mechanical support stability may be compromised
Solution Approach 1:
The patent incorporates support studs that extend from the RDL trace to the device substrate before the package bump is attached. This preliminary structural support is built into the metal skeleton structure during the same fabrication step as the RDL, ensuring mechanical stability is established in advance to prevent sagging or deformation during subsequent bump attachment processes
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
Reduces fabrication time and cost by eliminating the need for UBM formation, while maintaining robust mechanical and electrical connections through a single-step sputtering, electroplating, photo-resist stripping, and re-passivation process.
Implementation Method 1
a single-step sputtering, electroplating, photo-resist stripping, and re-passivation process
Implementation Method 2
a single-step sputtering, electroplating, photo-resist stripping, and re-passivation process
Implementation Method 3
a single-step sputtering, electroplating, photo-resist stripping, and re-passivation process
Data Source
AI summary
An IC package includes one or more microelectronic devices, a plurality of package bumps disposed at a first side, and a metal structure electrically connecting at least a first device contact pad of a first microelectronic device and at least a first package bump of the plurality of package bumps. The metal structure includes an RDL trace extending between a first region aligned with the first device contact pad and a second region aligned with the first package bump, wherein the first package bump is mechanically and electrically connected directly to the second region of the RDL trace. The metal structure further includes a first via extending between the first region of the RDL trace and the first device contact pad and further includes a set of one or more support studs extending from the second region to a support surface facing the first side.