Knife-Edge Probe Bumps for Fine-Pitch Temporary Wafer Bonding
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Solution Overview
Problem
Existing probe testing technologies are limited to chips with large interconnect pitches (≥50 µm) and lack a microfabrication process for fine-alignment and rework capability at room temperature, especially for IC wafers and chips with very fine-pitch interconnect pads (≤10 µm), which is crucial for known-good-die testing and integration processes.
Innovation Solution
The development of Small Pitch Integrated Knife Edge (SPIKE) probe bumps with shaped tips allows for temporary electrical connections at room temperature, enabling fine-pitch probing and temporary attachments, facilitating known-good-chiplet testing and integration by using microfabrication techniques to form weak metallurgical bonds that can be easily disengaged for rework.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional probe testing technology is used, then testing can be performed on chips with large interconnect pitches (≥50 µm), but it cannot achieve fine-pitch probing (≤10 µm) required for modern IC wafers and chips
Solution Approach 1:
The patent changes the physical parameters of the probe structure by transitioning from conventional rounded or flat probe tips to knife-edge shaped tips with significantly reduced radius of curvature. This parameter change enables the probe to achieve fine-pitch contacts (≤10 µm) by concentrating force at the sharp edge, allowing penetration through oxide layers and reliable electrical contact at much smaller pitch dimensions than conventional probes can achieve
Solution Approach 2:
The patent utilizes extreme curvature by implementing knife-edge tips with very small radius of curvature. The sharp, highly curved edge of the probe tip enables it to concentrate mechanical force into a tiny contact area, facilitating penetration through bond pad oxide layers and achieving reliable electrical contact at fine-pitch dimensions that would be impossible with conventional low-curvature probe tips
2Manufacturing precision
If temporary bonded alignment is implemented for fine-alignment capability, then room temperature operation with inspection and rework capability is achieved, but the bonding mechanism is not established in prior art
Solution Approach 1:
The patent applies preliminary action by performing temporary bonding at room temperature before final processing steps. This allows alignment verification, electrical testing, and potential rework to be completed before committing to permanent high-temperature bonding, thereby preventing waste of processing efforts on misaligned or defective devices
Solution Approach 2:
The patent implements dynamics by creating a temporary, reversible bonding state that can be easily formed and just as easily released. The bonding mechanism allows for dynamic adjustment and verification during the assembly process, enabling inspection and rework capabilities that static permanent bonding processes cannot provide
3Ease of manufacture
If standard microfabrication processes are used for probe formation, then integration with CMOS or other device technology is achieved, but fine-alignment capability at room temperature with rework capability is lacking
Solution Approach 1:
The patent achieves universality by demonstrating that standard microfabrication processes already capable of producing CMOS and other device technology can also produce the knife-edge probe structures. The same lithography, deposition, and etching tools used for device fabrication can manufacture the probes, eliminating the need for specialized equipment while achieving fine-pitch precision
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
Enables cost-effective known-good-chiplet testing and integration with a >100x cost reduction for large multi-chip modules, providing uniform low contact resistance across large arrays of bumps, and supporting >20,000 contacts with <1 ohm resistance, suitable for 2D and 3D integration applications.
Implementation Method 1
novel knife-edge microstructure contacts are disclosed that enable high local pressures to be applied that form weak temporary bonds to be established at room temperatures
Data Source
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AI summary
A temporary bond method and apparatus for allowing wafers, chips or chiplets. To be tested, the temporary bond method and apparatus comprising: a temporary connection apparatus having one of more knife-edged microstructures, wherein the temporary connection apparatus serves, in use, as a probe device for probing the chiplets, each chiplet including a die having one or more flat contact pads which mate with the one of more knife-edged microstructures of the temporary connection apparatus; a press apparatus for applying pressure between the one or more flat contact pads on the chiplet with the one of more knife-edged microstructures of the temporary connection apparatus thereby forming a temporary bond between the temporary connection pad with the knife-edged microstructure in contact with the one or more flat wafer pads; the press being able to apply a pressure to maintain the temporary bond connection during or prior to testing of the chiplet.