Selective Cap Deposition on Graphene Interconnects for Electromigration
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Solution Overview
Problem
The challenge of increased resistance and electromigration in metal lines with narrow widths in integrated circuits (ICs) due to tighter pitches in advanced fabrication processes, leading to performance issues and failure.
Innovation Solution
Implementing a layer of graphene over metal lines, optionally with a conductive cap such as cobalt, to reduce resistance and enhance electromigration reliability by selectively depositing a conductive cap over graphene-capped metal lines or growing graphene over cobalt-capped metal lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If metal line width is reduced to achieve tighter pitches, then device density increases, but resistance increases and electromigration performance deteriorates
Solution Approach 1:
The patent applies composite materials by combining graphene and cobalt to form a hybrid conductive cap structure. The graphene layer provides low resistance due to its high electron mobility, while the cobalt layer suppresses electromigration by providing structural stability. This composite approach allows narrow metal lines to maintain both low resistance and high electromigration resistance simultaneously, resolving the contradiction between device density and reliability.
2Area of moving object
If metal line width is reduced to achieve tighter pitches, then device density increases, but resistance increases
Solution Approach 1:
The graphene-cobalt composite cap structure addresses resistance issues by leveraging graphene's exceptional electrical conductivity. The graphene layer forms a low-resistance pathway for current flow, compensating for the increased resistance that would normally occur in narrower metal lines. This enables tighter pitches and higher device density without sacrificing electrical performance.
3Reliability
If conductive cap is deposited over graphene-capped metal lines, then electromigration reliability improves, but manufacturing complexity increases
Solution Approach 1:
The patent employs preliminary action by first depositing the graphene layer on the metal line before depositing the cobalt layer. The graphene layer is formed as a preliminary step that prepares the surface for subsequent cobalt deposition. This sequential approach, where each layer is deposited in a predetermined sequence, simplifies the manufacturing process compared to attempting to form the composite structure simultaneously, while still achieving the desired electromigration resistance.
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 combination of graphene and a conductive cap reduces resistance and improves electromigration performance in IC structures, enhancing the reliability and functionality of narrow metal lines.
Implementation Method 1
a layer of graphene over a metal line may reduce resistance
Implementation Method 2
selectively depositing a conductive cap over graphene-capped metal lines
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
Disclosed herein are integrated circuit (IC) structures fabricated with selective cap deposition techniques on graphene-capped conductive lines and IC structures and devices with graphene on capped conductive lines. In one example, an IC structure includes an interconnect layer with a conductive line, a conductive cap layer over the conductive line, and a layer of graphene between the conductive line and the conductive cap or a layer of graphene over the conductive cap. In one such example, the layer of graphene may enable lower resistance in the conductive line and the conductive cap may improve electromigration reliability.