Necked Interconnect Fuse Structure for IC Programming
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Solution Overview
Problem
Existing metal interconnect fuse architectures in integrated circuits face challenges with increasing fuse resistance and program current requirements as MOS transistor dimensions scale down, making it difficult to create an open fuse circuit efficiently.
Innovation Solution
The development of a necked interconnect fuse structure with a nominal and necked fuse segment, where the necked segment has a narrower lateral width than the nominal segment, allowing for a lower programming voltage to drive sufficient current and create an open circuit, utilizing a spacer-based double-patterning technique for fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If interconnect metal line fuse elements are used in advanced MOS ICs, then the fuse can provide overcurrent protection and programming capability, but the fuse resistance increases with technology scaling, requiring higher program voltages and reducing effectiveness
Solution Approach 1:
The fuse structure is divided into two distinct segments: a first fuse segment with wider lateral dimensions and a second fuse segment with narrower lateral dimensions. This segmentation allows the circuit to benefit from the lower resistance of the wider segment while the narrower segment provides the necessary current confinement and melting characteristics for effective programming at reduced voltages.
Solution Approach 2:
Different lateral dimensions are applied to different segments of the fuse structure. The first fuse segment has larger lateral dimensions to reduce overall resistance, while the second fuse segment has smaller lateral dimensions to concentrate current and facilitate melting. This local variation in geometry optimizes both electrical performance and programming effectiveness.
2Use of energy by moving object
If the fuse cross-section is reduced to achieve low program current, then the programming current requirement decreases, but the fuse resistance increases, making it difficult to create an open circuit
Solution Approach 1:
The fuse is segmented into a first portion with larger cross-section for low resistance and a second portion with smaller cross-section for low program current. This segmentation resolves the contradiction by distributing different functional requirements to different spatial regions of the same fuse structure.
Solution Approach 2:
The fuse structure employs local quality variation through different lateral dimensions in different segments. The wider first segment reduces overall resistance while the narrower second segment confines current to achieve low program current requirements, simultaneously addressing both contradictory requirements.
3Use of energy by moving object
If electromigration-based fuse architecture is used, then low program current can be achieved, but the design is incompatible with efforts to mitigate electromigration for improved device reliability
Solution Approach 1:
The invention changes the physical parameters of the fuse structure by introducing a dual-segment geometry with different lateral dimensions. This parameter change allows the fuse to achieve low program current through geometric confinement rather than relying on electromigration effects, thereby maintaining device reliability while achieving programming capability.
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 reduces the total resistance of the fuse circuit, enabling a low programming voltage (<1.8V) to open the necked fuse segment effectively, while maintaining dimensional control and ensuring the fuse circuit is compact and reliable.
Implementation Method 1
interconnect metal line resistance has trended up over recent IC technology generations. An increase in fuse resistance reduces current through a fuse element at a given supply voltage, making it more difficult to create an open fuse circuit
Implementation Method 2
utilizing a spacer-based double-patterning technique for fabrication
Data Source
Figure 1A~1B
Figure 2~4A
Figure 4B~5
AI summary
Interconnect fuse structures including a fuse with a necked line segment, as well as methods of fabricating such structures. A current driven by an applied fuse programming voltage may open necked fuse segments to affect operation of an IC. In embodiments, the fuse structure includes a pair of neighboring interconnect lines equidistant from a center interconnect line. In further embodiments, the center interconnect line, and at least one of the neighboring interconnect lines, include line segments of lateral widths that differ by a same, and complementary amount. In further embodiments, the center interconnect line is interconnected at opposite ends of a necked line segment. In further embodiments, the necked line segment is fabricated with pitch-reducing spacer-based patterning process.