Interconnect Structure With Metal Cap for Electromigration Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing interconnect structures in semiconductor integrated circuits (ICs) face issues with electromigration, leading to voids, hillocks, via bond defects, time-dependent dielectric breakdown, and resistive-conductive delay due to metal migration between metal lines and contact vias, especially with the introduction of smaller technology nodes and multi-gate devices.
Innovation Solution
A method for selectively depositing a metal cap layer over contact vias to space them apart from metal lines, using a selective deposition process that forms a metal feature with a convex top surface, thereby reducing metal migration and contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metal lines are placed close to contact vias to increase functional density, then productivity is improved, but electromigration causes metal migration leading to voids, hillocks, and via bond defects worsening reliability
Solution Approach 1:
A barrier layer is introduced as an intermediary substance between the metal line and contact via. This barrier layer prevents direct contact and metal migration while allowing electrical connection to be maintained, thus resolving the contradiction between high functional density and reliability by enabling close placement without electromigration damage
Solution Approach 2:
The contact structure is segmented into multiple layers: the contact via, the barrier layer, and the metal line. This segmentation separates the metal migration pathways, confining potential electromigration effects within the barrier layer and protecting the via from damage while maintaining the compact interconnect structure
2Reliability
If barrier layer thickness is increased to prevent metal migration, then reliability is improved, but manufacturing precision becomes more difficult due to tighter process control requirements
Solution Approach 1:
The barrier layer thickness is optimized to specific parameter ranges that provide sufficient migration prevention while remaining within manufacturable tolerances. By establishing precise thickness parameters and control windows, the invention balances reliability improvement with manufacturing feasibility
3Productivity
If geometry size is decreased to scale down circuits, then productivity is improved through increased functional density, but electromigration effects are intensified worsening reliability
Solution Approach 1:
The barrier layer serves as a protective intermediary that becomes increasingly critical as geometry scales down. At smaller dimensions where electromigration effects are amplified, the barrier layer provides enhanced protection by blocking migration pathways, enabling continued scaling while maintaining reliability
4Productivity
If contact via size is reduced to increase functional density, then productivity is improved, but contact resistance increases worsening device performance
Solution Approach 1:
The barrier layer is applied selectively at the critical interface between the contact via and metal line, providing localized protection where electromigration and contact resistance issues occur. This local application maintains via size for low resistance while preventing migration at the interface
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 metal cap layer effectively reduces electromigration, minimizing voids and hillocks, and decreases contact resistance, enhancing device performance and reliability by blocking electron transport paths and reducing interdiffusion.
Implementation Method 1
A self-aligned interconnect structure includes a contact via extending through a dielectric layer, a metal cap selectively formed over the contact via and spaced apart from the contact via by the dielectric layer, and a metal line over the metal cap
Implementation Method 2
A method for selectively depositing a metal cap layer over contact vias to space them apart from metal lines, using a selective deposition process that forms a metal feature with a convex top surface
Data Source
AI summary
A semiconductor structure includes a transistor, a conductive via extending through a dielectric layer and electrically connected to the transistor, a metal cap disposed on a first surface of the conductive via and a first portion of a second surface of the dielectric layer, and a metal line disposed around the metal cap. The metal line includes a barrier layer and a metal fill layer embedded in the barrier layer. The metal cap is embedded in the metal line. The barrier layer extends along a second portion of the second surface of the dielectric layer and is spaced apart from the conductive via.