Interfacial Dopant Caps for Electromigration Resistance in Damascene Interconnects
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Solution Overview
Problem
As integrated circuit (IC) devices miniaturize, electromigration failures increase due to high current densities causing metal atom migration and void formation in interconnects, particularly at the 45 nm technology node and beyond, where copper interconnects face significant reliability issues despite having better electromigration resistance than aluminum.
Innovation Solution
The formation of thin protective caps at the interface between metal lines and dielectric diffusion barrier layers using dopant elements like boron, aluminum, titanium, etc., which diffuse into the metal to form solid solutions, alloys, or compounds, reducing metal atom migration without significantly increasing interconnect resistance. These caps are created by depositing a dopant source layer, modifying it to form a passivated layer, and allowing the dopant to react with the metal, controlling the cap thickness and diffusion process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If interconnect dimensions are decreased during miniaturization, then device integration density is improved, but electromigration failure probability increases due to higher current densities
Solution Approach 1:
The patent applies local quality by creating a protective cap layer at the specific location where electromigration is most severe (the metal/dielectric interface). This cap layer has different properties than the bulk metal, providing localized protection against atom migration without affecting the overall interconnect dimensions or current carrying capacity.
Solution Approach 2:
The protective cap layer acts as an intermediary between the metal interconnect and the dielectric material. This intermediate layer prevents direct interaction that leads to electromigration, serving as a buffer that reduces metal atom migration while allowing the interconnect to maintain its electrical function.
2Reliability
If protective cap layers are formed at the metal/dielectric interface, then electromigration resistance is improved, but interconnect resistance increases
Solution Approach 1:
The patent applies partial action by forming a thin protective cap layer that provides sufficient electromigration protection without excessive thickness. This partial protection approach ensures that the cap layer is thick enough to prevent metal atom migration but thin enough to minimize its impact on electrical resistance and energy loss.
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 method improves electromigration performance and adhesion at the metal/dielectric interface, maintaining low interconnect resistance while enhancing the reliability of IC devices by effectively reducing metal atom migration and void formation.
Implementation Method 1
dopant elements like boron, aluminum, titanium, etc., which diffuse into the metal to form solid solutions, alloys, or compounds
Implementation Method 2
allowing the dopant to react with the metal, controlling the cap thickness and diffusion process
Data Source
AI summary
Protective caps residing at an interface between metal lines and dielectric diffusion barrier (or etch stop) layers are used to improve electromigration performance of interconnects. Protective caps are formed by depositing a source layer of dopant-generating material (e.g., material generating B, Al, Ti, etc.) over an exposed copper line, converting the upper portion of the source layer to a passivated layer (e.g., nitride or oxide) while allowing an unmodified portion of a dopant-generating source layer to remain in contact with copper, and, subsequently, allowing the dopant from the unmodified portion of source layer to controllably diffuse into and/or react with copper, thereby forming a thin protective cap within copper line. The cap may contain a solid solution or an alloy of copper with the dopant.