Superfilled Cobalt Contact Vias via Seed Layer Deposition
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Solution Overview
Problem
Current semiconductor technologies face challenges in filling contact vias with metal, leading to seams and voids that increase electrical resistance and degrade device performance, especially with the increasing miniaturization of contact vias, where it is difficult to control the deposition of copper and tungsten effectively.
Innovation Solution
A method involving the deposition of a seed layer of iridium, osmium, palladium, platinum, or ruthenium followed by electroplating cobalt into the contact via, which allows for complete filling without forming seams or voids, using a superfilling process that inhibits cobalt deposition on the walls, ensuring electrical conductivity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used to fill contact vias, then electrical conductivity is improved, but control of deposition process becomes difficult and copper migrates into dielectric materials
Solution Approach 1:
A barrier layer comprising titanium nitride and tungsten is introduced as an intermediary between copper and dielectric materials. The titanium nitride layer prevents copper diffusion into silicon and dielectric materials, while the tungsten layer provides additional barrier functionality. This mediator structure enables copper to be used in contact vias without the harmful migration effects.
2Manufacturing precision
If tungsten is used to fill contact vias, then deposition control is improved and migration into dielectric materials is reduced, but electrical conductivity deteriorates due to higher resistivity
Solution Approach 1:
The contact via structure uses a composite material approach, combining copper (high conductivity) with titanium nitride and tungsten (barrier properties). This composite structure achieves both low electrical resistance and prevention of metal migration, overcoming the limitations of using pure tungsten or pure copper.
3Productivity
If contact via size is reduced for miniaturization, then transistor density is improved, but formation of seams and voids during metal filling becomes more difficult to control
Solution Approach 1:
The dual-layer barrier structure of titanium nitride and tungsten serves as a mediator that enables reliable copper filling in miniaturized contact vias. This intermediary layer system provides the necessary control for seam-free and void-free metal filling even as contact via dimensions decrease, supporting continued transistor density improvement.
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 enables the formation of conductive vias with improved electrical conductivity and reliability by preventing the formation of seams and voids, even in high aspect ratio openings, thereby enhancing the performance of semiconductor devices.
Implementation Method 1
A seed layer can be deposited onto a surface of a dielectric layer overlying a semiconductor region of a wafer. The seed layer can also be deposited onto an interior surface of a hole in the dielectric layer.
Implementation Method 2
A CVD process deposits a layer of tungsten 10 conformally over the bottom surface 14 and over the wall 16 of a hole 12 in the dielectric layer.
Implementation Method 3
a layer consisting essentially of cobalt can be plated onto the seed layer to form a conductive via within the hole
Data Source
AI summary
In accordance with one aspect of the invention, a method is provided for fabricating a semiconductor element having a contact via. In such method, a hole can be formed in a dielectric layer to at least partially expose a region including at least one of semiconductor or conductive material. A seed layer can be deposited over a major surface of the dielectric layer and over a surface within the hole. In one embodiment, the seed layer can include a metal selected from the group consisting of iridium, osmium, palladium, platinum, rhodium, and ruthenium. A layer consisting essentially of cobalt can be electroplated over the seed layer within the hole to form a contact via in electrically conductive communication with the region.