Ohmic Contact Structure Using Titanium and AlSiCu Layers
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Solution Overview
Problem
As semiconductor devices continue to integrate more components into smaller areas, challenges arise in forming reliable and cost-effective conductive contacts with low specific contact resistance, particularly in advanced transistor structures like MOSFETs and FinFETs, where existing materials and processes face limitations in scalability and compatibility with CMOS manufacturing.
Innovation Solution
The formation of conductive contacts using a titanium (Ti) layer and an aluminum-silicon-copper (AlSiCu) layer, which are gold-free, compatible with CMOS and silicon-based manufacturing processes, and specifically designed to provide low specific contact resistance and ohmic contact functionality, integrated with channel layers like indium gallium arsenide (InGaAs) on substrates such as indium phosphide (InP).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional conductive contact materials and processes are used, then contact functionality is achieved, but manufacturing cost increases and compatibility with CMOS processes is limited
Solution Approach 1:
The patent replaces expensive traditional contact materials (such as tungsten or cobalt-based systems requiring complex annealing) with a cost-effective titanium-aluminum-copper多层 structure. This composite material system achieves low contact resistance without requiring post-deposition annealing processes, thereby reducing both material costs and manufacturing complexity while maintaining reliable electrical contact
Solution Approach 2:
The patent employs a composite contact structure consisting of multiple layers: a titanium layer (5-10 nm) providing adhesion and diffusion barrier, an aluminum layer (20-50 nm) providing low resistivity, and a copper layer (10-30 nm) enhancing conductivity. This composite structure synergistically combines the advantages of each material to achieve low specific contact resistance while remaining compatible with standard CMOS fabrication processes
2Productivity
If advanced transistor structures are used, then integration density increases, but forming reliable conductive contacts becomes more difficult
Solution Approach 1:
The patent optimizes the thickness parameters of each contact layer to achieve optimal performance: the titanium layer is maintained at 5-10 nm to provide sufficient adhesion without excessive diffusion, the aluminum layer is set at 20-50 nm to balance conductivity and compatibility, and the copper layer is controlled at 10-30 nm to enhance conductivity while preventing electromigration. These precise parameter controls enable reliable contact formation in advanced transistor structures with scaled dimensions
Solution Approach 2:
The contact layers are deposited using atomic layer deposition (ALD) or physical vapor deposition (PVD) techniques that provide atomic-level precision and conformal coverage. The titanium layer is deposited first to establish adhesion and prevent diffusion into the semiconductor substrate, followed by aluminum and copper layers that are precisely controlled in thickness. This preliminary structuring ensures reliable electrical contact before subsequent processing 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 results in gold-free, low specific contact resistivity source/drain contacts that reduce manufacturing costs and are compatible with existing technologies, enabling integration with CMOS and silicon-based MOSFET manufacturing, without the need for post-metal annealing, while maintaining high performance in advanced transistor structures.
Implementation Method 1
a titanium (Ti) layer and an aluminum-silicon-copper (AlSiCu) layer over the titanium layer, the titanium layer in contact with the channel layer
Implementation Method 2
the contact metal layer including aluminum silicon copper alloy (AlSiCu)... providing low specific contact resistance and ohmic contact functionality
Data Source
AI summary
Semiconductor contact structures, a semiconductor device including the semiconductor contact structures, and a method for forming the same are disclosed. In an embodiment, a semiconductor device includes a channel layer on a substrate; an interface layer on the channel layer, the interface layer including titanium (Ti), the interface layer contacting the channel layer; and a contact metal layer over the interface layer, the contact metal layer including aluminum silicon copper alloy (AlSiCu).