Pillar on Pad Interconnects with Full Diameter Contact
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Solution Overview
Problem
Conventional pillar on pad interconnect structures for semiconductor dice face issues with adhesion and reliability during stress testing, as the small exposed surface area of bond pads and the soft nature of polymer repassivation material lead to connectivity problems and electrical failures due to intermetallic compound formation and solder wetting issues.
Innovation Solution
The solution involves forming conductive elements directly on bond pads without polymer repassivation material, using a photodefinable material to create a structure where the conductive elements, including copper, nickel, and solder, are in full contact with the bond pads, and a photodefinable material is applied over the active surface and conductive elements, with controlled exposure to radiant energy to ensure adequate thickness and support for reliable connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If polymer repassivation material is used to protect bond pads, then the bond pads are protected from environmental damage, but the exposed surface area of bond pads is reduced and structural support is insufficient leading to adhesion failure
Solution Approach 1:
The patent removes the polymer repassivation material from over the bond pad area, extracting the harmful element that was causing adhesion failure. By eliminating this material, full exposure of the bond pad surface is achieved, providing both environmental protection through alternative means and adequate structural support for reliable adhesion during stress testing.
Solution Approach 2:
The patent applies different material properties to different locations: the bond pad area remains exposed without polymer coverage to ensure full surface contact and structural support, while other areas of the semiconductor device may still have appropriate protective coatings. This localized differentiation resolves the contradiction between protection and adhesion reliability.
2Productivity
If small diameter pillars are used to provide reliable electrical connections, then connection density is improved, but adhesion between pillars and bond pads deteriorates due to limited contact area
Solution Approach 1:
The patent changes the geometric parameters of the interconnect structure by transitioning from small diameter pillars to larger conductive elements that provide full diameter contact with bond pads. This parameter change maintains high connection density through optimized layout while improving adhesion reliability through increased contact area and better stress distribution.
3Device complexity
If conductive elements are formed with limited bond pad exposure, then manufacturing complexity is reduced, but connectivity reliability deteriorates due to lift-off during stress testing
Solution Approach 1:
The patent segments the device structure into distinct functional zones: exposed bond pad areas for reliable electrical connection and conductive elements with full diameter contact, separated from covered areas by removed polymer material. This segmentation allows each zone to perform its function optimally without the complications of overlapping material layers, maintaining manufacturing simplicity while ensuring connectivity reliability.
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 enhances the structural support and reliability of interconnects, increasing the yield of functional semiconductor dice by over 10% during reliability stress testing, such as HAST and Temperature Cycle tests, by maintaining the integrity of the bond between the conductive elements and bond pads.
Implementation Method 1
exposing the at least a top surface of the at least one conductive element to a dose of radiant energy sufficient to penetrate the second thickness of photodefinable material
Data Source
AI summary
Methods of fabricating interconnect structures for semiconductor dice comprise forming conductive elements in contact with bond pads on an active surface over a full pillar diameter of the conductive elements, followed by application of a photodefinable material comprising a photoresist to the active surface and over the conductive elements. The polyimide material is selectively exposed and developed to remove photodefinable material covering at least tops of the conductive elements. Semiconductor dice and semiconductor die assemblies are also disclosed.