Remote Plasma Oxide Reduction for Copper Interconnect Capping
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Solution Overview
Problem
The increasing current density of copper interconnects due to scaling down leads to enhanced electromigration issues, and conventional methods for depositing metal capping layers fail to adequately reduce the native oxide layer, resulting in high contact sheet resistance between the copper interconnects and the capping layer.
Innovation Solution
A method involving a remote plasma reducing step using a reducing gas containing hydrogen to remove native oxide layers from copper interconnects, followed by the deposition of a cobalt metal capping layer using selective chemical vapor deposition, within a specially designed processing platform that includes a degassing chamber, remote plasma reducing chamber, and deposition chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional degassing methods (argon or hydrogen) are used to remove native oxide layers, then the processing is simple, but the contact sheet resistance remains high and adhesion strength is insufficient
Solution Approach 1:
The processing platform is segmented into three distinct chambers (degassing chamber, remote plasma reducing chamber, and deposition chamber) to perform separate functions sequentially. This segmentation allows each chamber to be optimized for its specific purpose, enabling effective oxide removal and low-resistance contacts while maintaining overall system manageability through modular design.
Solution Approach 2:
A remote plasma reducing chamber is introduced as an intermediary step between degassing and deposition. This intermediate chamber uses plasma treatment to effectively reduce native oxide layers before capping layer deposition, serving as a mediator that bridges the gap between simple degassing and high-quality adhesion, thereby reducing contact resistance without requiring complex direct coupling of degassing and deposition processes.
2Length of moving object
If copper interconnect dimension is scaled down to increase current density, then interconnect size is reduced, but electromigration resistance deteriorates
Solution Approach 1:
The native oxide layer on copper interconnects is removed through preliminary degassing and remote plasma treatment before the capping layer is deposited. This preliminary action of oxide removal creates a fresh, clean copper surface that enables strong adhesion of the capping layer, which subsequently provides effective protection against electromigration in scaled-down interconnects.
Solution Approach 2:
The processing is conducted in an inert atmosphere environment within vacuum chambers to prevent re-oxidation of the copper interconnect surface after oxide removal. This inert environment maintains the reduced copper surface until the capping layer is deposited, ensuring the adhesion quality and electromigration resistance are preserved.
3Strength
If native oxide layer is not effectively removed, then processing is simple, but adhesion strength and contact quality deteriorate
Solution Approach 1:
The processing platform enables continuous operation through sequential chambers, where wafers progress from degassing to remote plasma reduction to deposition without breaking vacuum. This continuous useful action effectively removes oxide layers and deposits high-adhesion capping layers while maintaining processing efficiency through uninterrupted workflow and automated wafer transfer.
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
This approach effectively reduces the native oxide layer, enhancing the adhesion strength and quality of the metal capping layer, significantly decreasing contact resistance and improving the reliability of copper interconnects, as evidenced by nearly complete reduction of copper oxide and extended chip performance without failures for at least 600 hours.
Implementation Method 1
A native oxide layer on a copper interconnect in a damascene structure on a substrate is reduced by a remote plasma generated by a reducing gas containing hydrogen
Implementation Method 2
A cobalt layer is formed on the copper interconnect to be a metal capping layer
Data Source
AI summary
Before depositing a metal capping layer on a metal interconnect in a damascene structure, a remote plasma is used to reduce native oxide formed on the metal interconnect. Accordingly, a remote plasma reducing chamber is integrated in a processing platform for depositing a metal capping layer.