Flared Pillar Ends for Current Crowding in Microelectronic Interconnects
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Solution Overview
Problem
Microelectronic devices with pillars connected to bump bonds experience current crowding, leading to hot spots and voids, which reduce the reliability of the pillars during operation.
Innovation Solution
The microelectronic device design includes a die with a conductor and a pillar that has a die-side flared end and a head-side flared end, where the flare extensions are greater than specific dimensions, reducing current density at both ends of the pillar, thereby enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pillar with uniform cross-section is used, then the manufacturing process is simple, but current crowding occurs leading to hot spots and voids
Solution Approach 1:
The pillar structure is designed with different cross-sectional areas at different locations: a first cross-sectional area at the first end, a second cross-sectional area at the second end, and a third cross-sectional area in the middle portion. This local variation in geometry allows current density to be distributed more evenly throughout the pillar, preventing current crowding at the ends while maintaining manufacturing feasibility through standard semiconductor fabrication processes.
2Reliability
If current flows through a uniform pillar, then electrical connection is established, but current crowding generates hot spots that reduce reliability
Solution Approach 1:
By varying the cross-sectional area of the pillar along its length, the current density is redistributed to achieve more uniform heating throughout the pillar structure. This prevents localized hot spots that would otherwise form at the ends of uniform pillars, thereby improving operational stability and reliability.
3Reliability
If current flows through the pillar, then electrical function is performed, but voids form due to current crowding
Solution Approach 1:
The non-uniform cross-sectional areas at different portions of the pillar create a more uniform current density distribution, which prevents the concentration of current that leads to void formation. This structural variation ensures reliable electrical connection by eliminating the harmful effect of current-induced voids.
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 flared ends effectively reduce current density, improving the reliability of the pillars by minimizing the formation of voids and hot spots, thus enhancing the operational stability of the microelectronic devices.
Implementation Method 1
The pillar has a die-side flared end at the die end of the pillar, wherein the die-side flared end extends outward by a distance that is greater than a lesser of half a thickness of the die conductor and half a lateral width of the pillar midway between a die end and a head end. The pillar has a head-side flared end at the head end of the pillar, wherein the head-side flared end extends outward by a distance that is greater than a lesser of half a thickness of the head and half the lateral width of the pillar.
Data Source
AI summary
A microelectronic device has a die with a die conductor at a connection surface. The microelectronic device includes a pillar electrically coupled to the die conductor, and a head electrically coupled to the pillar. The pillar has a die-side flared end at a die end of the pillar; the pillar widens progressively along the die-side flared end, and extends outward by more than a lesser of half a thickness of the die conductor and half a lateral width of the pillar midway between a die end and a head end. The pillar has a head-side flared end at a head end of the pillar; the pillar widens progressively along the die-side flared end, and extends outward by a distance that is greater than a lesser of half a thickness of the head and half the lateral width of the pillar. Methods of forming the microelectronic device are disclosed.