Cobalt Electrochemical Plating for Void-Free Sub-Micron Filling
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Solution Overview
Problem
As microelectronic device features shrink, traditional copper plating processes struggle to achieve void-free fill due to the increasing volume of low-conductivity barrier layers required to prevent copper diffusion, leading to unacceptable resistance in interconnects and other features.
Innovation Solution
The use of cobalt or nickel electrochemical deposition with specific pH-controlled plating solutions and subsequent annealing to minimize seed layer corrosion and seam line defects, allowing for conformal or super conformal filling without the need for a barrier layer, and improving film properties and reducing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper plating with barrier layer is used, then copper diffusion prevention is improved, but interconnect resistance increases due to low-conductivity barrier layer occupying larger volume in smaller features
Solution Approach 1:
The patent extracts and removes the barrier layer from the structure by using cobalt or nickel plating that does not require a barrier layer, thereby eliminating the source of high resistance while maintaining copper diffusion prevention through the inherent properties of the alternative金属材料
Solution Approach 2:
The patent changes the material parameter from copper to cobalt or nickel, which have different diffusion characteristics and do not require barrier layers, thereby resolving the contradiction between diffusion prevention and resistance
2Length of moving object
If feature size is reduced, then device scaling is improved, but void-free fill becomes more difficult with traditional copper plating processes
Solution Approach 1:
The patent changes the plating chemistry parameters by using alkaline or neutral pH plating solutions instead of traditional acid copper chemistries, which enables better control of deposition kinetics and achieves void-free fill in smaller features
Solution Approach 2:
The patent uses composite plating approaches combining electroless seed layers with electrochemical deposition, and employs multi-step plating processes to achieve complete void-free fill in sub-micron features
3Reliability
If barrier layer thickness is maintained at minimum to prevent copper diffusion, then diffusion prevention is improved, but the proportion of barrier layer volume increases in smaller features leading to higher resistance
Solution Approach 1:
The patent extracts and eliminates the barrier layer entirely by using cobalt or nickel plating materials that do not diffuse into silicon or dielectric, removing the problematic component while maintaining the protective function
Solution Approach 2:
Instead of using copper with a barrier layer to prevent diffusion, the patent inverts the approach by using cobalt or nickel that inherently prevents diffusion without requiring an additional barrier layer
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 method effectively fills sub-micron features with cobalt or nickel, reducing seed layer corrosion and seam line defects, and decreases line resistance, making it suitable for high-volume manufacturing and maintaining conductivity without the need for a barrier layer.
Implementation Method 1
a cobalt or nickel conformal or super conformal film is plated onto the seed layer
Implementation Method 2
subsequent annealing to minimize seed layer corrosion and seam line defects
Data Source
AI summary
An electrochemical process for applying a conductive film onto a substrate having a seed layer includes placing the substrate into contact with an electrochemical plating bath containing cobalt or nickel, with the plating bath having pH of 4.0 to 9.0. Electric current is conducted through the bath to the substrate. The cobalt or nickel ions in the bath deposit onto the seed layer. The plating bath may contain cobalt chloride and glycine. The electric current may range from 1-50 milli-ampere per square cm. After completion of the electrochemical process, the substrate may be removed from the plating bath, rinsed and dried, and then annealed at a temperature of 200 to 400 C to improve the material properties and reduce seam line defects. The plating and anneal process may be performed through multiple cycles.