Cobalt-AlN Stack for Copper Interconnect Electromigration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The increasing circuit density and current density in semiconductor devices lead to decreased resilience of interconnect structures to electromigration, causing delamination and a drop in electrical properties due to poor adhesion between copper and low dielectric constant materials.
Innovation Solution
A semiconductor device is manufactured with a copper interconnect structure that includes a cobalt layer and an aluminum nitride (AlN) layer, deposited using selective chemical vapor deposition processes, to enhance adhesion and prevent electromigration by forming a stack of cobalt and AlN on the copper layer, which improves the adhesion between the copper and the etch stop layer and prevents delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If copper interconnect structure is used with low dielectric constant materials, then circuit density and current density increase, but adhesion between copper and etch stop layer deteriorates causing delamination
Solution Approach 1:
A cobalt layer is introduced as an intermediary between the copper interconnect structure and the etch stop layer. This cobalt layer serves as a mediator that improves adhesion between the copper and etch stop layer, preventing delamination while allowing the copper interconnect structure to function at high circuit density. The cobalt layer acts as a bonding interface that resolves the adhesion problem without compromising the high-density circuit design.
Solution Approach 2:
The patent creates a composite structure consisting of copper interconnect, cobalt adhesion layer, and etch stop layer. This composite material approach combines the high conductivity of copper with the adhesion properties of cobalt and the protective properties of the etch stop layer, achieving both high circuit density and reliable adhesion through material composition rather than relying on direct copper-to-etch-stop-layer bonding.
2Productivity
If copper interconnect structure is used with increasing current density, then circuit performance improves, but electromigration resistance decreases causing delamination
Solution Approach 1:
The cobalt layer serves as a protective intermediary that reduces electromigration effects. By placing the cobalt layer between the copper interconnect and the etch stop layer, it acts as a barrier that prevents copper atoms from migrating under high current density conditions, thereby maintaining electromigration resistance while allowing high current density operation.
Solution Approach 2:
The cobalt layer is deposited beforehand to provide a protective cushion against electromigration damage. This pre-deposited layer creates a buffer zone that absorbs and mitigates the harmful effects of electromigration before they can cause delamination between the copper interconnect and etch stop layer, enabling reliable high-current operation.
3Reliability
If cobalt layer is deposited using selective chemical vapor deposition, then adhesion and electromigration resistance improve, but manufacturing process complexity increases
Solution Approach 1:
The selective chemical vapor deposition process deposits cobalt only in specific locations where it is needed - on the copper interconnect surfaces that require adhesion enhancement and electromigration protection. This localized deposition approach improves reliability where necessary without requiring complex processing for the entire device, thereby managing manufacturing complexity through spatially selective processing.
Solution Approach 2:
The patent utilizes specific deposition parameters (temperature, pressure, precursor selection) to achieve selective cobalt deposition. By controlling these parameters, the process achieves high adhesion and electromigration resistance through precise parameter optimization rather than through complex multi-step procedures, simplifying the overall manufacturing process while maintaining high reliability.
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 solution effectively reduces electromigration and improves the adhesion between the copper layer and the etch stop layer, significantly enhancing the reliability and electrical properties of the semiconductor device by preventing interlayer delamination.
Implementation Method 1
The cobalt layer is formed using a selective chemical vapor deposition process
Implementation Method 2
submitting the aluminum layer to a nitrogen-containing plasma gas treatment to convert the aluminum layer to an aluminum nitride layer
Data Source
AI summary
A method of manufacturing a semiconductor device includes providing a semiconductor substrate, sequentially forming an etch stop layer and an interlayer dielectric layer on the semiconductor substrate, forming a copper metal interconnect structure in the interlayer dielectric layer, forming a copper layer in the copper metal interconnect structure, forming a cobalt layer on the copper layer, and forming an aluminum nitride layer on the cobalt layer. The stack of cobalt layer and copper layer effectively suppresses electromigration caused by diffusion of the copper layer into the interlayer dielectric layer, improves the adhesion between the copper layer and the etch stop layer, and prevents delamination.