Dual Silicide Structure for Integrated Circuit Reliability
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Solution Overview
Problem
Existing siliciding processes in semiconductor devices face issues such as gate-to-source/drain junction short-circuits, particularly due to the diffusion of nickel silicide, which degrades the performance of integrated circuits.
Innovation Solution
A dual silicide structure is formed by depositing cobalt as a bottom silicide metal with a thickness under 10 Å and nickel as a top silicide metal with a thickness of 80 Å to 100 Å, preventing nickel silicide diffusion and forming a cobalt silicide layer that blocks diffusion, thereby addressing short-circuit issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nickel silicide is used to reduce electrical resistance, then electrical performance is improved, but gate-to-source/drain junction short-circuits occur due to nickel silicide diffusion
Solution Approach 1:
A cobalt silicide layer is introduced as an intermediary barrier between the nickel silicide and the source/drain junctions. This cobalt silicide layer prevents nickel silicide from diffusing to the junctions while allowing the nickel silicide to maintain low electrical resistance in the contact regions, thus resolving the contradiction between electrical performance and short-circuit prevention.
Solution Approach 2:
The silicide structure is segmented into multiple functional layers: a bottom cobalt silicide layer that acts as a diffusion barrier, a middle nickel silicide layer that provides low resistance, and controlled thicknesses of each layer to achieve both electrical performance and junction protection. This segmentation allows each layer to perform its specific function without interfering negatively with others.
2Device complexity
If a single silicide layer is used to simplify the structure, then device complexity is reduced, but diffusion control and short-circuit prevention are insufficient
Solution Approach 1:
The silicide structure is divided into distinct layers with specific thicknesses and compositions. The cobalt silicide layer (5-15 nm) serves as a diffusion barrier, while the nickel silicide layer (20-50 nm) provides low resistance. This segmentation enables independent optimization of each layer's function, achieving both structural manageability and effective diffusion control.
Solution Approach 2:
The patent employs a composite silicide structure combining cobalt silicide and nickel silicide layers. Each material contributes its advantageous properties: cobalt silicide provides excellent diffusion barrier characteristics, while nickel silicide offers superior electrical conductivity. The composite structure achieves performance that neither material could provide alone.
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 prevents gate-to-source/drain junction short-circuits by blocking nickel silicide diffusion, enhancing the electrical performance and reliability of integrated circuits.
Implementation Method 1
forming a cobalt silicide layer that blocks diffusion
Implementation Method 2
A bottom silicide metal is deposited on the source/drain junction and then a top silicide metal is deposited on the bottom silicide metal
Data Source
AI summary
An integrated circuit is provided. A gate dielectric is formed on a semiconductor substrate, and a gate is formed over the gate dielectric. A sidewall spacer is formed around the gate and a source/drain junction is formed in the semiconductor substrate using the sidewall spacer. A bottom silicide metal is deposited on the source/drain junction and then a top silicide metal is deposited on the bottom silicide metal. The bottom and top silicide metals are formed into their silicides. A dielectric layer is deposited above the semiconductor substrate and a contact is formed in the dielectric layer to the top silicide.