Cobalt Capping Layer for Copper Hybrid Bonding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In hybrid bonding of semiconductor devices, copper migration during thermal expansion leads to void formation and diffusion issues, causing leakage and reducing the electromigration (EM) life of the bonded structure.
Innovation Solution
Incorporating a capping layer with a conductive material like cobalt at the bonding interface to prevent copper diffusion and void formation, which is selectively deposited at the upper end of the bonding contact, improving the bonding interface properties and simplifying the fabrication process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper bonding contacts are used in hybrid bonding, then electrical conductivity is improved, but copper migration during thermal expansion causes void formation and diffusion issues
Solution Approach 1:
A capping layer comprising cobalt is deposited on the copper bonding contact to serve as an intermediary barrier. This capping layer prevents copper atoms from migrating during thermal expansion while maintaining electrical conductivity, thereby resolving the contradiction between conductivity and copper migration resistance
Solution Approach 2:
The bonding contact structure is transformed from pure copper to a composite structure consisting of copper bonding contact with a cobalt capping layer. This composite structure combines the high electrical conductivity of copper with the migration-resistant properties of cobalt, simultaneously achieving both improved conductivity and reduced copper migration
2Reliability
If a capping layer is added to prevent copper diffusion, then reliability is improved, but device complexity increases
Solution Approach 1:
The capping layer is applied selectively only to the bonding contact regions where copper migration is a problem, rather than uniformly across the entire device. This localized approach improves reliability at the bonding interface while minimizing the increase in overall device complexity
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 capping layer effectively reduces copper diffusion, voids, and leakage, thereby enhancing the EM life and reliability of the bonded structure while maintaining a cost-effective and simplified fabrication process.
Implementation Method 1
Incorporating a capping layer with a conductive material like cobalt at the bonding interface to prevent copper diffusion
Implementation Method 2
copper migration during thermal expansion leads to void formation
Data Source
AI summary
Embodiments of bonded semiconductor structures and fabrication methods thereof are disclosed. In an example, a method for forming a semiconductor device is disclosed. A first device layer is formed on a first substrate. A first bonding layer including a first bonding contact is formed above the first device layer. A first capping layer is formed at an upper end of the first bonding contact. The first capping layer has a conductive material different from a remainder of the first bonding contact. A second device layer is formed on a second substrate. A second bonding layer including a second bonding contact is formed above the second device layer. The first substrate and the second substrate are bonded in a face-to-face manner, so that the first bonding contact is in contact with the second bonding contact by the first capping layer.