BEOL Line Fuse With Localized Grain Refinement
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Solution Overview
Problem
Conventional BEOL eFUSE structures require high programming currents due to the larger cross-sectional area of line fuses, making them less efficient and more complex compared to via fuses, and the introduction of high-k metal gate materials in advanced semiconductor technologies has exacerbated these challenges.
Innovation Solution
A BEOL line fuse structure is formed with a region of conductive crystalline material having a smaller average grain size than the nominal grain size of the remaining portion, allowing for preferential electromigration at lower programming currents by creating a defined region with increased grain boundaries, which reduces electrical resistance and facilitates controlled fuse programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If line fuses are used in BEOL eFUSE structures, then wiring connectivity is improved, but programming current requirement increases
Solution Approach 1:
The patent applies local quality by creating a region with smaller grain size within the line fuse structure. This localized region has increased grain boundaries that facilitate electromigration at lower currents, while the rest of the line maintains larger grain size for optimal conductivity. The selective modification of grain size in a specific region allows the line fuse to be programmed at lower currents than conventional uniform line fuses.
2Reliability
If higher programming currents are applied to blow line fuses, then fuse programming is achieved, but device reliability deteriorates
Solution Approach 1:
The patent changes the physical parameter of grain size in a specific region of the line fuse. By reducing the grain size in the programmed region, the density of grain boundaries increases, which provides more pathways for electromigration. This parameter change enables the fuse to be blown at lower programming currents, thereby improving device reliability by reducing stress on the structure during programming.
3Device complexity
If conventional line fuse structures are used, then wiring simplicity is maintained, but programming efficiency decreases
Solution Approach 1:
The patent segments the line fuse structure into regions with different grain sizes. The majority of the line maintains larger grain size for low resistance, while a specific region has smaller grain size to facilitate programming. This segmentation allows the structure to exhibit both low overall resistance and localized programming capability, improving programming efficiency without compromising wiring simplicity.
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 BEOL line fuse structure can be programmed at significantly lower currents than conventional line fuses, enhancing reliability and simplifying eFUSE cell design while maintaining high electrical conductivity in the majority of the wiring, thus addressing the inefficiencies and complexities of traditional BEOL processing.
Implementation Method 1
allowing for preferential electromigration at lower programming currents by creating a defined region with increased grain boundaries
Implementation Method 2
annealing the exposed top surface of the conductive crystalline material in the line using a programmable energy source
Implementation Method 3
annealing the exposed top surface of the conductive crystalline material in the line using a programmable energy source
Data Source
AI summary
In one embodiment, the invention provides a back-end-of-line (BEOL) line fuse structure. The BEOL line fuse structure includes: a line including a plurality of grains of conductive crystalline material; wherein the plurality of grains in a region between the first end and a second end include an average grain size that is smaller than a nominal grain size of the plurality of grains in a remaining portion of the line.