Copper-Alloy Adhesion Layer for Void-Free Fine-Pitch Interconnect Fill
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Solution Overview
Problem
Copper fill in narrow spaces within semiconductor devices is challenging due to incomplete coverage and void formation, especially in fine-pitch copper interconnect structures, leading to electrical opens and reduced chip yield, primarily because of the low mobility of copper on adhesion layers and insufficient thermal stability of these layers during reflow processes.
Innovation Solution
A thermally stable copper-alloy adhesion layer is formed using a metallic nitride liner and an alloy of copper with non-copper transition metals, such as Co, Ru, Ta, and Mo, which enhances adhesion and remains conformal during anneal processes, preventing void formation by intermixing copper with transition metals to create a continuous copper fill without defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If copper is deposited to form fine-pitch copper interconnect structures, then copper interconnect structures are formed, but copper tends to agglomerate on the adhesion layer due to low mobility, causing voids and electrical opens
Solution Approach 1:
The patent modifies the adhesion layer composition by incorporating specific transition metals (Co, Ru, Ta, Mo) at controlled concentrations (0.1-10 atomic percent) to change the surface properties and copper mobility characteristics, enabling continuous copper fill without agglomeration
Solution Approach 2:
The patent creates a composite adhesion layer system combining traditional adhesion materials (TiN, TaN) with copper-alloy layers containing transition metals, where each layer performs specific functions: the nitride liner provides adhesion to the dielectric, while the copper-alloy layer provides thermal stability and controlled copper mobility
2Reliability
If a conventional adhesion layer is used, then copper deposition is facilitated, but insufficient thermal stability causes holes to form within the adhesion layer during copper reflow process
Solution Approach 1:
The patent changes the thermal stability parameter by selecting transition metals with high melting points and forming them into alloy structures with copper, where the transition metal content (0.1-10 atomic percent) is optimized to prevent hole formation during reflow while maintaining adhesion properties
Solution Approach 2:
The patent forms a composite copper-alloy adhesion layer where transition metals (Co, Ru, Ta, Mo) are integrated into the copper matrix, creating a material that combines the adhesion properties of copper with the thermal stability of transition metals, preventing structural degradation during high-temperature reflow
3Length of moving object
If copper fill is performed in narrow spaces, then fine-pitch interconnect structures are achieved, but incomplete coverage of underlying surfaces occurs, leading to voids
Solution Approach 1:
The patent modifies the copper deposition parameters by controlling the adhesion layer composition to achieve optimal copper mobility, enabling complete coverage of narrow spaces at fine pitch dimensions without void formation
Solution Approach 2:
The patent applies different compositions within the adhesion layer structure, with transition metals strategically positioned to locally enhance copper mobility and adhesion where needed, ensuring complete coverage in narrow interconnect spaces while maintaining overall structural integrity
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 ensures continuous copper coverage and fill without voids, even at small dimensions, thereby increasing the yield and reliability of semiconductor devices by suppressing copper agglomeration and maintaining structural integrity during thermal processing.
Implementation Method 1
enhances adhesion and remains conformal during anneal processes, preventing void formation by intermixing copper with transition metals
Data Source
AI summary
An opening is formed through a dielectric material layer to physically expose a top surface of a conductive material portion in, or over, a substrate. A metallic nitride liner is formed on a sidewall of the opening and on the top surface of the conductive material portion. A metallic adhesion layer including an alloy of copper and at least one transition metal that is not copper is formed on an inner sidewall of the metallic nitride liner. A copper fill material portion may be formed on an inner sidewall of the metallic adhesion layer. The metallic adhesion layer is thermally stable, and remains free of holes during subsequent thermal processes, which may include reflow of the copper fill material portion. An additional copper fill material portion may be optionally deposited after a reflow process.