Composite Contact Plug with Cobalt Liner for Low Resistance
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Solution Overview
Problem
As semiconductor devices scale to smaller sub-micron sizes, it becomes challenging to reduce contact plug resistance while decreasing contact hole size, requiring improved structures and manufacturing methods for effective interconnects.
Innovation Solution
A composite contact plug structure featuring a bilayer structure with a cobalt or ruthenium conductive liner and a tungsten, cobalt, or ruthenium conductive core, along with a diffusion barrier layer of tantalum or tantalum nitride, which maintains low resistivity, good adhesion, high activation energy, and electro-migration resistance, and allows for fine-tuning of stress characteristics through controlled layer thicknesses and angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If contact hole size is decreased to scale to smaller sub-micron sizes, then device integration density is improved, but contact plug resistance increases
Solution Approach 1:
The patent applies composite materials by creating a multi-layer contact plug structure consisting of a conductive liner layer (cobalt or ruthenium) and a conductive core layer (tungsten, cobalt, or ruthenium). This composite structure allows the contact plug to maintain low resistance even as contact hole dimensions are reduced, resolving the contradiction between scaling down contact hole size and maintaining acceptable contact resistance.
Solution Approach 2:
The patent implements local quality by assigning different materials with specific properties to different regions of the contact plug. The conductive liner layer provides adhesion and electro-migration resistance at the interface with the substrate, while the conductive core layer provides bulk conductivity. This localized optimization of material properties enables the contact plug to perform multiple functions simultaneously, maintaining reliability despite reduced overall size.
2Length of moving object
If contact plug dimensions are reduced, then device scaling is achieved, but adhesion properties deteriorate
Solution Approach 1:
The conductive liner layer made of cobalt or ruthenium serves as an adhesion-promoting interface layer between the substrate and the conductive core layer. This composite structure ensures that even as overall contact plug dimensions are reduced, the adhesion properties are maintained through the specialized functionality of the liner layer, which is optimized for bonding at the interface.
3Length of moving object
If contact plug dimensions are reduced, then device scaling is achieved, but electro-migration resistance deteriorates
Solution Approach 1:
The conductive liner layer (cobalt or ruthenium) acts as a diffusion barrier that prevents electro-migration of atoms from the conductive core layer to the surrounding dielectric material. This composite structure maintains electro-migration resistance even as contact plug dimensions are reduced, because the liner layer provides a protective interface that blocks atomic diffusion paths.
4Device complexity
If single-layer contact plug structure is used, then manufacturing simplicity is maintained, but performance at advanced nodes is insufficient
Solution Approach 1:
The contact plug is segmented into two distinct functional layers: a conductive liner layer and a conductive core layer. This segmentation allows each layer to be optimized for its specific function (adhesion/electro-migration resistance for the liner, bulk conductivity for the core), improving overall performance at advanced technology nodes while maintaining a relatively simple two-step manufacturing process.
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 composite contact plug structure enables scalable, low-resistance, high-performance interconnects with improved adhesion and electro-migration resistance, suitable for advanced node applications by effectively managing stress and resistance characteristics.
Implementation Method 1
Another advantageous feature of some embodiments is that the bilayer plug exhibits high activation energy and melting point, which provides for good electro-migration (EM) resistance and electrical performance
Implementation Method 2
A typical contact plug may include tungsten (W) due to its low resistivity (about 5.4 μΩ·cm) and high reliability
Data Source
AI summary
An embodiment contact plug includes a bilayer structure and a diffusion barrier layer on a sidewall and a bottom surface of the bilayer structure. The bilayer structure includes a conductive core and a conductive liner on a sidewall and a bottom surface of the conductive core. In the embodiment contact plug, the conductive liner comprises cobalt or ruthenium.