Alpha-Phase Ta Barrier Layer Contact Resistance Reduction
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving low resistance and reliability in interconnect structures due to the high contact resistivity of tantalum (Ta) barrier layers, which limit the performance of integrated circuits as they become more complex, and the β-phase Ta barrier layer's unsatisfactory properties in contact resistance.
Innovation Solution
An α-phase inducing metal layer is introduced on a first Ta barrier layer of β phase to induce the subsequent deposition of Ta into an α-phase Ta barrier layer, reducing contact resistance by forming a predominantly α-phase Ta barrier layer with lower resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Ta barrier layer is used to block copper diffusion, then the blocking performance is improved, but the contact resistivity increases significantly
Solution Approach 1:
The Ta barrier layer is segmented into two distinct layers with different crystal phases: a bottom layer with β-phase structure providing superior blocking performance, and a top layer with α-phase structure providing lower contact resistivity. This segmentation allows each layer to optimize its function independently, resolving the contradiction between blocking performance and contact resistivity.
Solution Approach 2:
Different regions of the Ta barrier layer are assigned different crystal phases with different properties. The bottom layer (near the copper interface) uses β-phase for maximum diffusion blocking, while the top layer (near the ILD interface) uses α-phase for minimum contact resistance. This local differentiation of material properties resolves the contradiction by optimizing each region for its specific function.
2Ease of manufacture
If conventional deposition techniques are used for Ta barrier layer, then the process is simple, but the contact resistivity remains high
Solution Approach 1:
The crystal phase parameter of the Ta barrier layer is changed from单一的β-phase to a two-phase structure (β-phase at bottom, α-phase at top). This parameter change in crystal structure fundamentally alters the electrical properties at the contact interface, reducing contact resistivity while maintaining the deposition process simplicity through sequential deposition of two layers.
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
The α-phase Ta barrier layer achieves a nearly 20% lower contact resistance compared to conventional β-phase Ta barrier layers, enhancing the performance and reliability of interconnect structures in semiconductor devices.
Implementation Method 1
an α-phase inducing metal layer is introduced on a first Ta barrier layer of β phase to induce the subsequent deposition of Ta into an α-phase Ta barrier layer
Data Source
AI summary
An improved interconnect structure and a method for forming the interconnect structure is disclosed that allows the interconnect structure to achieve a lower Rc. To lower the Rc of the interconnect structure, an α-phase inducing metal layer is introduced on a first Ta barrier layer of β phase to induce the subsequent deposition of Ta thereon into the formation of an α-phase Ta barrier layer. The subsequently deposited Ta barrier layer with a primary crystallographic structure of α phase has a lower Rc than that of the β-phase Ta barrier layer.