Dome-Shaped Bump Terminal Structure for Semiconductor Miniaturization
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Solution Overview
Problem
Conventional bump shapes in semiconductor devices limit bump pitch reduction due to their mushroom shape, causing shorting and inadequate filling around the bumps, which restricts miniaturization efforts.
Innovation Solution
A terminal structure with a dome-shaped bump where the maximum diameter is located lower than the under-bump metal layer's height, using a tin-based bump with a nickel under-bump metal layer to prevent diffusion and ensure proper filling and electrical insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional mushroom-shaped bumps are used, then the bump formation process is simple, but the bump pitch cannot be reduced sufficiently due to shorting between adjacent bumps
Solution Approach 1:
The patent inverts the conventional bump shape logic: instead of having the maximum diameter at the top (mushroom shape), the bump is designed with the maximum diameter at the bottom, forming a dome shape. This inversion prevents adjacent bumps from contacting each other at their widest points, enabling reduced bump pitch while maintaining electrical isolation.
Solution Approach 2:
The patent changes the geometric parameters of the bump by controlling the solidification process to achieve a dome shape where the maximum diameter occurs at the bottom rather than the top. This parameter change in shape geometry directly enables closer bump spacing without shorting.
2Device complexity
If conventional mushroom-shaped bumps are used, then the bump structure is simple, but fillings cannot be sufficiently wrapped around the bump base portion
Solution Approach 1:
By inverting the bump shape to have the maximum diameter at the bottom, the patent creates a geometry that naturally facilitates wrapping of fillings around the bump base. The dome shape with narrower top provides better mechanical interlocking and coverage for the filling materials during the mounting process.
3Productivity
If bump pitch is reduced, then device miniaturization is achieved, but adjacent bumps may short to each other
Solution Approach 1:
The inverted dome shape with maximum diameter at the bottom ensures that the widest part of each bump is positioned lower, creating natural spacing between adjacent bumps at their upper portions. This geometric configuration maintains electrical insulation even when bumps are placed closer together, enabling device miniaturization without shorting.
4Ease of manufacture
If tin-based bump material is used, then dome shape formation is facilitated, but metal diffusion into the electrode may occur
Solution Approach 1:
The patent introduces a multi-layer under-bump metal structure consisting of a first under-bump metal layer (in contact with the electrode) and a second under-bump metal layer (in contact with the tin-based bump). This intermediary structure acts as a diffusion barrier, preventing tin atoms from migrating into the electrode while maintaining the ease of dome shape formation.
Solution Approach 2:
The patent employs composite material structure with multiple metal layers having different properties. The first under-bump metal layer provides good adhesion to the electrode, while the second under-bump metal layer provides compatibility with the tin-based bump and prevents diffusion, creating a functionally composite structure.
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 configuration allows for reduced bump pitch without shorting and enables effective filling with resins and fillers, supporting the miniaturization of semiconductor devices.
Implementation Method 1
the under-bump metal layer preferably contains nickel (Ni) as a main component. This makes it possible to suitably suppress the metal contained in the bump from diffusing into the external electrode
Implementation Method 2
the bump preferably contains tin (Sn) as a main component. This causes the bump to have a suitable dome shape, leading to that the height at which the bump has a maximum diameter can be easily located lower than the maximum height of the under-bump metal layer
Data Source
AI summary
The present invention relates to a terminal structure comprising: a base material 10; an external electrode 20 formed on the base material; an insulating coating layer 30 formed on the base material and on the electrode and having an opening exposing at least part of the electrode; an under-bump metal layer 70 filling the opening and covering part of the insulating coating layer; and a dome-shaped bump 85 covering the under-bump metal layer, wherein in a cross section along a lamination direction, a height Hbm at which the bump has a maximum diameter (Lbm) is lower than a maximum height Hu of the under-bump metal layer.