Hybrid Self-Aligned Via Interconnect for TDDB-Resistant Chips
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Solution Overview
Problem
As the size of components within integrated chips decreases, the distance between neighboring metal lines and/or vias also decreases, increasing the likelihood of time-dependent dielectric breakdown (TDDB) and leakage currents between adjacent metal lines and/or vias, which can lead to short circuits and reduced reliability of the integrated chip.
Innovation Solution
The integrated chip employs a hybrid interconnect structure that includes a first plurality of metal lines made of a first conductive material, with a second conductive material having a greater resistance to diffusion directly over the first conductive material. This structure is vertically coupled with via layers made of the second conductive material, which reduces the diffusion of metal atoms into the dielectric layers and decreases the likelihood of TDDB.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the distance between neighboring metal lines and/or vias is decreased to increase component density, then the component density is improved, but the likelihood of time-dependent dielectric breakdown and leakage currents increases
Solution Approach 1:
The patent applies local quality by using different conductive materials in different locations within the same interconnect structure. Specifically, a first conductive material (e.g., copper) is used for metal lines where low resistance is critical, while a second conductive material (e.g., cobalt or tungsten) with higher diffusion resistance is used for vias and regions closer to dielectric layers where diffusion prevention is critical. This spatial differentiation of material properties allows the structure to simultaneously achieve high density and high reliability.
Solution Approach 2:
The patent employs composite materials by combining multiple conductive materials within a single interconnect structure. The hybrid interconnect structure integrates a first conductive material for low-resistance connections and a second conductive material with superior diffusion resistance. This composite approach allows different regions of the interconnect to exhibit optimized properties: the first material provides electrical performance while the second material provides diffusion barrier functionality, resolving the contradiction between density and reliability.
2Reliability
If a barrier layer is added to prevent diffusion of metal atoms into dielectric layers, then the reliability is improved, but the resistance of via layers increases
Solution Approach 1:
The patent applies parameter changes by selecting conductive materials with fundamentally different diffusion characteristics rather than adding a separate barrier layer. The second conductive material (e.g., cobalt or tungsten) is chosen specifically for its inherently low diffusion coefficient into dielectric materials. By changing the material parameter (diffusion resistance) rather than adding a structural layer, the patent achieves diffusion prevention without introducing additional resistance that would occur with a barrier layer approach.
Solution Approach 2:
The patent extracts the barrier function from a separate barrier layer and integrates it directly into the conductive material itself. Instead of having a distinct barrier layer between the via and dielectric, the via is made of a conductive material that inherently resists diffusion. This extraction of the barrier function from a separate component and integration into the functional material eliminates the need for additional layers while maintaining both low resistance and diffusion prevention.
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 hybrid interconnect structure effectively mitigates TDDB and leakage currents, enhancing the reliability of the integrated chip without the need to increase the distance between neighboring metal lines and/or vias, and also reduces the resistance of the via layers by eliminating the need for barrier layers.
Implementation Method 1
the second conductive material and the third conductive material have lower diffusion coefficients than the first conductive material
Data Source
AI summary
An interconnect structure is provided. The interconnect structure includes a first metal line. The first metal line includes a first conductive material disposed within a first dielectric layer over a substrate and a second conductive material disposed within the first dielectric layer and directly over a top of the first conductive material. The second conductive material is different from the first conductive material. A second dielectric layer is disposed over the first dielectric layer. A first via comprising a third conductive material is disposed within the second dielectric layer and on a top of the second conductive material. The second conductive material and the third conductive material have lower diffusion coefficients than the first conductive material.