Contact Barrier Structure for Copper Diffusion Control
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Solution Overview
Problem
In modern integrated circuits, the increasing aspect ratio of contact plugs leads to discontinuous contact barriers, allowing copper to diffuse into semiconductor devices, causing leakage currents and potential device failure due to tungsten's low conductivity being replaced by copper, which has a higher diffusion rate.
Innovation Solution
A semiconductor structure with a contact barrier layer comprising different materials encircling the contact, where a metal layer forms a silicide region and remains unreacted to act as a diffusion barrier, preventing copper diffusion into source/drain regions and gate electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used to replace tungsten for forming contacts, then contact conductivity is improved, but copper diffusion into source/drain regions and gate electrode increases
Solution Approach 1:
A contact barrier layer is introduced as an intermediary between the copper contact and the underlying source/drain regions and gate electrode. This barrier layer physically separates the copper from the semiconductor structures, preventing copper diffusion while allowing the high conductivity benefit of copper contacts to be realized.
Solution Approach 2:
The contact structure uses a composite material approach by combining copper (for high conductivity) with a contact barrier layer material (for diffusion prevention). This composite structure leverages the strengths of each material while mitigating their weaknesses, achieving both low resistance and diffusion protection.
2Productivity
If contact plug width is reduced to achieve down-scaling, then device density is improved, but aspect ratio of contacts increases
Solution Approach 1:
The contact barrier layer is selectively applied to specific regions where copper diffusion is most problematic, such as the bottom and sidewalls of the contact opening. This localized approach provides effective diffusion protection without requiring uniform thick barriers throughout the entire contact structure, enabling better control of high aspect ratio contacts.
3Ease of manufacture
If contact barrier thickness is reduced to accommodate high aspect ratio contacts, then manufacturing is simplified, but contact barrier continuity is compromised
Solution Approach 1:
The contact barrier structure transitions from a purely vertical dimension to include lateral extension, forming a mesh-like or interconnected structure that provides continuous diffusion protection. This dimensional change allows the barrier to maintain continuity and effectiveness even with reduced thickness, accommodating high aspect ratio contacts while preventing copper diffusion.
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 reduces copper diffusion into semiconductor devices, improving contact conductivity and preventing device failure by maintaining a sufficient thickness of the metal layer to act as a barrier, even in high aspect ratio contacts.
Implementation Method 1
reacting the metal layer with the silicon-containing component to form a silicide region
Data Source
AI summary
A semiconductor structure includes a semiconductor substrate; a gate dielectric over the semiconductor substrate; a gate electrode over the gate dielectric; a source/drain region adjacent the gate dielectric; a silicide region on the source/drain region; a metal layer on top of, and physical contacting, the silicide region; an inter-layer dielectric (ILD) over the metal layer; and a contact opening in the ILD. The metal layer is exposed through the contact opening. The metal layer further extends under the ILD. The semiconductor structure further includes a contact in the contact opening.