Metal-Capped Interconnect Vias for Chalcogen Barrier Doping
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Solution Overview
Problem
As integrated circuits scale downward in size, reducing the thickness of interconnect structures while maintaining barrier performance becomes challenging, as thinner tantalum nitride barrier layers are ineffective and reactive gases like sulfur or selenium can cause copper extrusion and structural damage.
Innovation Solution
Implementing a capping layer of less reactive metals such as ruthenium, tungsten, or molybdenum over copper vias to protect against reactive gases, and doping tantalum-based barriers with sulfur or selenium to enhance barrier properties, allowing for thinner layers without copper extrusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the thickness of tantalum nitride barrier layers is reduced to enable further scaling, then interconnect structure dimensions can be reduced, but barrier performance deteriorates and metal atom diffusion increases
Solution Approach 1:
The patent employs a composite barrier structure consisting of multiple layers with different materials and functions. The barrier layer includes a first portion (e.g., tantalum nitride) and a second portion (e.g., tungsten or molybdenum) with distinct properties. This composite approach allows each layer to contribute its strengths: the first portion provides baseline barrier performance while the second portion enhances resistance to metal atom diffusion, enabling thinner overall structures without sacrificing reliability.
Solution Approach 2:
The barrier layer is designed with spatially varying composition and thickness. The first portion and second portion are positioned at different locations within the barrier structure, with the second portion strategically placed to address specific diffusion pathways. This local differentiation allows optimized barrier performance at critical interfaces while maintaining overall structural integrity and enabling reduced total thickness.
2Reliability
If sulfur or selenium are introduced to dope the barrier layer to enhance barrier properties, then barrier performance improves, but copper extrusion and structural damage occur
Solution Approach 1:
The patent introduces a capping layer as an intermediary between the copper interconnect and the sulfur- or selenium-doped barrier layer. This capping layer acts as a protective mediator that prevents direct contact between the reactive dopants and copper atoms. The capping layer allows the doped barrier to provide enhanced barrier performance while blocking the harmful interaction that would otherwise cause copper extrusion and structural damage.
Solution Approach 2:
The patent converts the potentially harmful effect of sulfur or selenium (which cause copper extrusion when in direct contact with copper) into a beneficial barrier enhancement. By using the capping layer to control the interaction, the dopants are confined to enhancing the barrier properties of the tantalum nitride without reaching the copper. The harmful reactivity is thus transformed into useful barrier strengthening through controlled spatial separation.
3Ease of manufacture
If standard barrier layers are used in thinner dimensions, then manufacturing cost is reduced, but adequate barrier performance cannot be achieved
Solution Approach 1:
The patent implements a multi-layer composite barrier structure where each layer is optimized for specific functions. The combination of different materials (tantalum nitride, tungsten, molybdenum) in a composite arrangement provides superior barrier performance compared to a single thick layer, while the overall thickness remains reduced. This composite approach achieves adequate barrier performance at thinner dimensions, reducing manufacturing complexity and cost.
Solution Approach 2:
The patent optimizes multiple parameters of the barrier structure simultaneously: material composition, layer thickness distribution, and dopant concentration. By carefully adjusting these parameters, the barrier achieves maximum performance at minimum thickness. The first and second portions have different thicknesses and compositions optimized for their respective functions, enabling cost-effective manufacturing with adequate performance.
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 prevents copper extrusion and maintains conductivity by using less reactive metals as capping layers and strengthening tantalum-based barriers with sulfur or selenium, enabling thinner interconnect structures with improved barrier performance.
Implementation Method 1
Implementing a capping layer of less reactive metals such as ruthenium, tungsten, or molybdenum over copper vias to protect against reactive gases
Implementation Method 2
doping tantalum-based barriers with sulfur or selenium to enhance barrier properties, allowing for thinner layers without copper extrusion
Data Source
AI summary
Techniques are provided herein for forming interconnect structures, such as conductive vias or contacts, that are protected from subsequent processing that includes reactive gas or plasma. A conductive via or contact within an interconnect layer may be formed with a capping layer having a different material to protect the underlying metal material from reacting with certain reactive gas or plasma elements. In some examples, a ruthenium capping layer is formed over a copper via to protect the copper. Other capping layer materials may include tungsten, cobalt, or molybdenum. In some embodiments, the entire conductive via may be formed using one of ruthenium, tungsten, cobalt, or molybdenum, to avoid the use of more reactive metals, such as copper. The capping layer (or less reactive metals) are used to protect the via during a barrier layer doping process that uses a gas or plasma including a chalcogen element (e.g., sulfur and/or selenium).