Nitridation Process for Semiconductor Contact Plug Barrier
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Solution Overview
Problem
The heat treatment process used to form metal silicide layers in semiconductor devices deteriorates the characteristics of the barrier layer, leading to increased resistance and defects in the contact plug, particularly due to the thin thickness and poor barrier characteristics of the metal nitride layer.
Innovation Solution
A method involving a nitridation process is employed to enhance the barrier characteristics of the metal nitride layer by increasing its nitrogen concentration and reducing oxygen, resulting in a contact plug with lower resistance and improved compactness, where the nitrogen concentration of the first metal pattern decreases from the outer sidewall to zero, and the metal nitride pattern has a thickness equal to or less than 3 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment is performed to form metal silicide layer, then resistance between source/drain region and contact plug is reduced, but characteristics of barrier layer are deteriorated
Solution Approach 1:
A nitrogen concentration gradient layer is formed in the barrier layer before heat treatment to prevent nitrogen loss during subsequent thermal processing. This preliminary nitrogen enrichment ensures that even after heat treatment, the barrier layer maintains adequate nitrogen concentration for low resistance while preserving other barrier characteristics.
Solution Approach 2:
The barrier layer is engineered with a nitrogen concentration gradient, where nitrogen concentration varies through the thickness of the layer. The region adjacent to the metal silicide layer has higher nitrogen concentration to maintain low resistance, while other regions maintain appropriate barrier characteristics, creating spatially differentiated properties within a single layer.
2Volume of moving object
If metal nitride layer thickness is reduced to achieve compactness, then contact plug size is reduced, but barrier characteristics deteriorate
Solution Approach 1:
The barrier layer incorporates a nitrogen concentration gradient where nitrogen concentration is higher near the metal silicide interface and lower toward the top surface. This localized nitrogen enrichment at the critical interface region provides effective barrier characteristics even when the overall layer thickness is reduced, enabling compact contact plugs with maintained reliability.
Solution Approach 2:
Instead of uniformly increasing layer thickness to improve barrier characteristics, the invention changes the nitrogen concentration parameter through the layer thickness. This parameter modification allows thin layers to achieve adequate barrier properties through non-uniform composition rather than relying on thickness 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
The nitridation process enhances the barrier characteristics of the metal nitride layer, reducing resistance and preventing defects such as voids or seams, while maintaining low resistance and good adhesion, thus improving the overall performance of the contact plug.
Implementation Method 1
a nitrogen concentration of the first metal pattern may gradually decrease according to a distance from the outer sidewall of the metal nitride pattern
Data Source
AI summary
A semiconductor device includes an active fin partially protruding from an isolation pattern on a substrate, a gate structure on the active fin, a source/drain layer on a portion of the active fin adjacent to the gate structure, a source/drain layer on a portion of the active fin adjacent to the gate structure, a metal silicide pattern on the source/drain layer, and a plug on the metal silicide pattern. The plug includes a second metal pattern, a metal nitride pattern contacting an upper surface of the metal silicide pattern and covering a bottom and a sidewall of the second metal pattern, and a first metal pattern on the metal silicide pattern, the first metal pattern covering an outer sidewall of the metal nitride pattern. A nitrogen concentration of the first metal pattern gradually decreases according to a distance from the outer sidewall of the metal nitride pattern.