Aluminum Intermediate Layer for Copper Etching Control
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Solution Overview
Problem
The challenge in semiconductor manufacturing lies in the complexity of integrating copper into uppermost metallization levels due to its inability to be etched using plasma etching techniques, resulting in issues like uneven etching rates, lateral undercuts, and rough sidewalls, which complicates the formation of thick copper lines required for high current density applications.
Innovation Solution
Incorporating an intermediate layer comprising aluminum between the copper power metal and the barrier layer enables selective wet chemical etching, improving etch profile control and achieving uniform copper line profiles by acting as a selective etch stop and adhesion promoter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If plasma etching is used to etch copper power metal, then etching can be performed, but uneven etching rates, lateral undercuts, and rough sidewalls occur
Solution Approach 1:
An intermediate layer comprising aluminum is introduced between the copper power metal and the barrier layer. This intermediate layer acts as a mediator that enables selective wet chemical etching, improving etch profile control and achieving uniform copper line profiles while preventing direct interaction between copper and the barrier layer that causes etching defects.
2Reliability
If thick copper lines are formed for high current density applications, then current carrying capacity is improved, but etching complexity and profile control difficulty increase
Solution Approach 1:
The aluminum intermediate layer serves as a selective etch stop layer that simplifies the etching process for thick copper lines. By providing a distinct etching target with different etch selectivity, it enables controlled removal of copper material while maintaining profile uniformity, thereby reducing etching process complexity despite the increased copper thickness.
Solution Approach 2:
The intermediate layer is strategically positioned only where needed - between the copper power metal and the barrier layer. This localized intervention provides etching control exactly where required without affecting other aspects of the structure, enabling simplified processing of thick copper regions while maintaining overall device integrity.
3Manufacturing precision
If an intermediate layer is added between copper and barrier layer, then etch profile control is improved, but layer structure complexity increases
Solution Approach 1:
The aluminum intermediate layer performs multiple functions simultaneously: it acts as a selective etch stop layer for profile control, provides adhesion promotion between copper and barrier layer, and serves as a diffusion barrier. By consolidating these functions into a single layer, the overall structural complexity is minimized while achieving multiple objectives.
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 allows for homogeneous etching of copper power metals, reducing line roughness and variations in thickness, thereby facilitating the fabrication of thick copper lines with improved uniformity and adhesion, overcoming the limitations of conventional etching methods.
Implementation Method 1
Using wet chemical etching, a metal line is formed by etching the metal layer, the intermediate layer, and the diffusion barrier liner
Implementation Method 2
The intermediate layer has a different etch selectivity from the power metal layer. The wet chemical etching is selective between the intermediate layer and the power metal layer
Implementation Method 3
The diffusion barrier layer is a diffusion barrier to copper atoms from the power metal layer
Implementation Method 4
Incorporating an intermediate layer comprising aluminum between the copper power metal and the barrier layer enables selective wet chemical etching, improving etch profile control and achieving uniform copper line profiles by acting as a selective etch stop and adhesion promoter
Data Source
AI summary
A method of forming a metallization layer over a semiconductor substrate includes depositing a blanket layer of a diffusion barrier liner over an inter level dielectric layer, and depositing a blanket layer of an intermediate layer over the diffusion barrier liner. A blanket layer of a power metal layer including copper is deposited over the intermediate layer. The intermediate layer includes a solid solution of a majority element and copper. The intermediate layer has a different etch selectivity from the power metal layer. After depositing the power metal layer, structuring the power metal layer, the intermediate layer, and the diffusion barrier liner.