Copper Electroplating on Cobalt Liners for Void-Free Submicron Features
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Solution Overview
Problem
Conventional electroplating methods face challenges in scaling interconnect metallization to narrower geometries, resulting in defects like overhangs and sidewall voiding, which lead to electrical shorts and reliability issues in advanced microprocessors.
Innovation Solution
An electroplating process using an alkaline complexed-copper electrolyte bath with a combination of forward and reverse direct current pulses is employed for direct copper deposition on a cobalt liner, minimizing seam and center voids in features by promoting uniform copper nucleation and deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If physical vapor deposition (PVD) is used to deposit copper on cobalt liner, then copper deposition is achieved, but protrusion or overhang at feature opening occurs leading to pinch-off
Solution Approach 1:
The patent replaces physical vapor deposition (PVD) with electroplating for copper deposition. This substitution of deposition mechanism eliminates the line-of-sight deposition limitation of PVD, preventing overhang and protrusion defects while achieving conformal coverage of narrow features.
Solution Approach 2:
The patent employs pulse electroplating with specific parameters (pulse width, duty cycle, current density) to control copper deposition. By optimizing these parameters, the process achieves uniform deposition in narrow features without forming overhangs or protrusions that would cause pinch-off.
2Manufacturing precision
If conventional electroplating is used for copper deposition in narrow features, then copper filling is achieved, but sidewall voiding occurs
Solution Approach 1:
The patent uses pulse electroplating with periodic on/off cycles instead of continuous DC plating. The pulsed current allows copper ions to diffuse away from the cathode surface during off-periods, preventing concentration buildup that causes voiding, while maintaining efficient deposition during on-periods.
Solution Approach 2:
The patent optimizes electroplating parameters including pulse width (1-100 ms), duty cycle (10-90%), and current density (0.1-10 mA/cm²) to achieve void-free filling. These parameter adjustments control the deposition kinetics to ensure uniform copper distribution without sidewall voiding in narrow features.
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 ensures void-free plating and improved reliability by preventing sidewall voiding and minimizing defects, enhancing the electrical integrity of submicron features in advanced microprocessors.
Implementation Method 1
copper electrodeposition in the presence of additives can produce void-free plating of submicron features
Implementation Method 2
direct copper electrodeposition onto conformal diffusion-barriers such as cobalt
Implementation Method 3
electrodeposition chemistries that enable copper nucleation and uniform deposition on the wafer
Data Source
AI summary
In one example, an electroplating system comprises a bath reservoir, a holding device, an anode, a direct current power supply, and a controller. The bath reservoir contains an electrolyte solution. The holding device holds a wafer submerged in the electrolyte solution. The wafer comprises features covered by a cobalt layer. The anode is opposite to the wafer and submerged in the electrolyte solution. The direct current power supply generates a direct current between the holding device and the anode. A combination of forward and reverse pulses is applied between the holding device and the anode to electroplate a copper layer on the cobalt layer of the wafer.