Cobalt Metal Plug Via Structure for IC Interconnect Precision
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Solution Overview
Problem
As semiconductor devices become smaller and more complex, the BEOL metallization process faces challenges in maintaining precise dimensions of vias, especially at the point of contact with metal lines, due to increasing complexity and the need for smaller metallization structures.
Innovation Solution
The process involves forming a metal plug of cobalt or its alloy within a via opening, with an aspect ratio greater than 0.3, which is directly in contact with the underlying metal routing path, and filling the remaining opening with metal material to define a second metal routing path, ensuring precise dimensions and contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If via dimensions are reduced to meet smaller device requirements, then device scaling is achieved, but manufacturing precision of via dimensions deteriorates
Solution Approach 1:
The via structure is segmented into two distinct parts: a metal plug at the bottom and a metal fill material above it. The metal plug is formed first with controlled dimensions, then the remaining via opening is filled with metal material. This segmentation allows independent optimization of each part's formation process, enabling precise control of the overall via dimension even as via size decreases.
Solution Approach 2:
The metal plug is formed in advance before filling the remaining via opening with metal material. By preliminarily forming the metal plug with controlled dimensions and properties, the foundation for precise via dimension control is established early in the process, allowing subsequent steps to build upon this precise foundation.
2Reliability
If via contact with metal line is optimized, then electrical connection reliability is improved, but process complexity increases
Solution Approach 1:
Different materials are used for different parts of the via structure: cobalt or cobalt-containing alloy for the metal plug at the bottom, and copper or other conductive material for the upper fill. This local differentiation optimizes the contact region with cobalt's superior adhesion and electrical properties, while using cost-effective materials for the upper portion, achieving reliable contact without uniformly complicating the entire process.
Solution Approach 2:
The via structure employs composite materials with cobalt or cobalt-containing alloy combined with other conductive materials. This composite approach leverages the advantageous properties of each material: cobalt provides excellent adhesion and electrical contact at the critical interface with the underlying metal line, while the fill material completes the conductive path, achieving reliable electrical connection through material composition rather than process 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
This approach allows for accurate control of via dimensions and maintains the desired contact with metal lines, enhancing the reliability and performance of interconnect structures in integrated circuits.
Implementation Method 1
depositing a metal plug at a bottom of the via opening in direct contact with the first metal routing path
Implementation Method 2
depositing a metal plug at a bottom of the via opening in direct contact with the first metal routing path
Data Source
AI summary
An integrated circuit includes first and second metallization levels. The first metallization level includes a first metal routing path. The second metallization level includes a dielectric layer having a via opening formed therein extending vertically through the dielectric layer to reach a top surface of the first metal routing path. A metal plug is deposited at a bottom of the via opening in direct contact with the first metal routing path. A remaining open area of the via opening is filled with a metal material to define a second metal routing path. The metal plug is formed of cobalt or an alloy including cobalt, and has an aspect ratio of greater than 0.3.