Flip Chip UBM Guard Ring Contact for Uniform Bump Size
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Solution Overview
Problem
Conventional methods for forming conductive bumps in flip chip packages result in size differences due to thickness variations in the under bump metallurgy (UBM) layer, leading to increased resistance and poor electrical joint reliability.
Innovation Solution
The UBM layer is directly contacted with the guard ring, ensuring a uniform current flow regardless of thickness differences, allowing for the formation of conductive bumps with consistent sizes through an electroplating process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UBM layer is formed on the insulating layer pattern with a trench, then the guard ring can be formed to prevent sudden current flow, but the UBM layer thickness becomes non-uniform causing conductive bump size variation
Solution Approach 1:
The patent applies local quality by forming the UBM layer with different thicknesses in different regions: a first thickness in the first region and a second thickness in the second region. This localized thickness variation allows the UBM layer to compensate for the trench structure, ensuring uniform conductive bump formation across the substrate while maintaining the guard ring's current protection function.
Solution Approach 2:
The patent implements preliminary action by pre-forming the UBM layer with compensated thickness distribution before the electroplating process. The UBM layer is designed with greater thickness in regions adjacent to trenches where current density would naturally be lower, ensuring that when electroplating occurs, uniform conductive bumps are formed despite the underlying topography variations.
2Reliability
If the UBM layer has varying thickness due to trench structure, then the guard ring function is maintained, but current flow becomes non-uniform increasing resistance
Solution Approach 1:
The UBM layer is designed with locally optimized thickness: thicker regions are positioned where the trench structure would cause current concentration, while thinner regions are positioned where current flow is already sufficient. This local quality adjustment ensures uniform current density distribution across the entire UBM layer, reducing overall resistance while preserving the guard ring's protective function.
3Productivity
If the conductive bumps have different sizes, then the electroplating process completes, but contact area varies reducing electrical joint reliability
Solution Approach 1:
The patent changes the physical parameter of the UBM layer thickness to compensate for trench-induced current distribution issues. By adjusting the UBM layer thickness profile (first thickness in first region, second thickness in second region), the effective plating surface is modified to produce uniform conductive bump sizes despite variations in underlying current density, ensuring consistent contact areas and reliable electrical joints.
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 ensures conductive bumps of uniform size, enhancing the electrical joint reliability of flip chip packages by maintaining consistent contact areas.
Implementation Method 1
An electroplating process can be performed on the UBM layer to form the conductive bumps on the UBM layer.
Data Source
AI summary
A semiconductor device can include a semiconductor chip, a protective layer pattern, an under bump metallurgy (UBM) layer, and conductive bumps. The semiconductor chip can include a pad and a guard ring. The protective layer pattern can be formed on the semiconductor chip to expose the pad and the guard ring. The UBM layer can be formed on the protective layer and can directly make contact with the pad and the guard ring. The conductive bumps can be formed on a portion of the UBM layer on the pad. Thus, the UBM layer and the guard ring can directly make contact with each other, so that a uniform current can be provided to the UBM layer on the pad regardless of a thick difference of different portions of the UBM layer.