Copper Electroplating on Cobalt Liners via Two-Bath Sequence
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional electroplating methods face challenges in scaling interconnect metallization to narrower geometries, resulting in defects like protrusion, overhang, and sidewall voiding when copper is deposited on cobalt liners, leading to electrical shorts and reliability issues.
Innovation Solution
A two-bath electroplating sequence is employed, where a first alkaline copper-complexed bath is used for copper nucleation and a second acidic copper bath for filling features, minimizing sidewall voiding and seam defects by preventing cobalt dissolution and ensuring uniform deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If physical vapor deposition (PVD) of copper on cobalt liner is used, then copper deposition is achieved, but protrusion and overhang defects occur at feature opening
Solution Approach 1:
The patent changes the chemical parameters of the plating bath by using an alkaline copper-complexed bath instead of conventional acidic baths. This parameter change prevents cobalt dissolution and eliminates protrusion/overhang defects while achieving uniform copper deposition on cobalt liners in submicron features.
Solution Approach 2:
The patent employs a composite plating solution containing copper complexes in an alkaline environment with specific additives. This composite chemical system enables selective copper deposition on cobalt surfaces without the harmful side effects of conventional single-component plating baths.
2Manufacturing precision
If conventional electroplating with additives is used for submicron features, then void-free plating is achieved, but sidewall voiding occurs after plating
Solution Approach 1:
The patent changes the pH parameter to alkaline conditions and uses copper-complexed chemistry, which fundamentally alters the deposition mechanism. This prevents sidewall voiding while maintaining void-free filling of submicron features, improving both manufacturing precision and reliability.
3Productivity
If scaling to narrower geometries is attempted, then interconnect density is improved, but process difficulty increases
Solution Approach 1:
The patent uses alkaline copper-complexed plating bath parameters that enable reliable copper deposition on cobalt liners even at sub-50 nm node dimensions. This parameter change simplifies the overall metallization process by eliminating the need for complex seed layer structures and multiple plating steps.
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 direct copper deposition on cobalt liners without seams or voids in vias and trenches, enhancing the reliability and performance of advanced microprocessors by maintaining uniformity and preventing defects.
Implementation Method 1
a first copper layer is deposited on a wafer in a first electroplating bath using a first electroplating chemistry
Implementation Method 2
conventional acid baths can result in cobalt dissolution
Data Source
AI summary
In one example, an electroplating system comprises a first bath reservoir, a second bath reservoir, a clamp, a first anode in the first bath reservoir, a second anode in the second bath reservoir, and a direct current power supply. The first bath reservoir contains a first electrolyte solution that includes an alkaline copper-complexed solution. The second bath reservoir contains a second electrolyte solution that includes an acidic copper plating solution. The direct current power supply generates a first direct current between the clamp and the first anode to electroplate a first copper layer on the cobalt layer of the wafer submerged in the first electrolyte solution. The direct current power supply then generates a second direct current between the clamp and the second anode to electroplate a second copper layer on the first copper layer of the wafer submerged in the second electrolyte solution.