Cobalt Reflow Metallization for Interconnect RC Delay
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As integrated circuit dimensions shrink, conventional lithography faces challenges in creating smaller structures, leading to increased resistance-capacitance (RC) delay due to higher copper resistivity, which affects signal speed and overall circuit performance.
Innovation Solution
A method involving a multiple fill metallization process using a ruthenium and cobalt layer combination, where a cobalt layer is reflowed to fill features, reducing aspect ratios and improving metal fill properties, electromigration resistance, and reliability of interconnects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If copper interconnect dimensions are reduced to improve circuit integration density, then more circuit features can be packaged closer together, but copper resistivity increases causing increased RC delay
Solution Approach 1:
The patent uses a composite interconnect structure consisting of multiple materials: copper base layer, ruthenium layer, and cobalt layer. This composite structure combines the advantages of each material - copper provides high conductivity, while ruthenium and cobalt layers reduce resistivity and prevent copper migration, thereby maintaining low RC delay at reduced dimensions
Solution Approach 2:
The patent changes the material composition parameters of the interconnect structure by introducing ruthenium and cobalt layers. This parameter change modifies the electrical properties (resistivity) and structural properties (migration resistance) of the interconnect, enabling continued scaling without proportionate increase in RC delay
2Ease of manufacture
If conventional lithography is used to create smaller structures, then manufacturing process is simple, but manufacturing precision deteriorates as dimensions shrink below lithography capabilities
Solution Approach 1:
The patent segments the interconnect formation process into multiple distinct steps: copper deposition, ruthenium layer deposition, and cobalt layer deposition. Each step can be optimized independently with appropriate deposition techniques, allowing precise control of each layer's thickness and properties to achieve the required manufacturing precision for scaled features
3Productivity
If copper interconnects are used at reduced dimensions, then circuit packaging density improves, but electromigration resistance deteriorates due to higher current density
Solution Approach 1:
The ruthenium and cobalt layers act as intermediary protective layers between the copper conductors and the environment. These layers prevent copper surface migration and electromigration by providing a stable diffusion barrier, thereby maintaining electromigration resistance even as copper interconnect dimensions are reduced for higher packaging density
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 ruthenium/cobalt combination effectively reduces RC delays, enhances metal fill properties, and improves the reliability of interconnects by providing better lattice matching and reduced copper surface migration, thus improving the performance of aggressively scaled features.
Implementation Method 1
Using a physical vapor deposition process, a cobalt layer is deposited disposed over the ruthenium layer
Implementation Method 2
A thermal anneal reflows the cobalt layer to fill a second portion of the set of features
Data Source
AI summary
A method for constructing an advance conductor structure is described. A pattern is provided in a dielectric layer in which a set of features are patterned for a set of metal conductor structures. An adhesion promoting layer is created disposed over the patterned dielectric. A metal layer is deposited to fill a first portion of the set of features disposed the adhesion promoting layer. A ruthenium layer is deposited disposed over the metal layer. Using a physical vapor deposition process, a cobalt layer is deposited disposed over the ruthenium layer. A thermal anneal reflows the cobalt layer to fill a second portion of the set of features.