Carbon Interface Liner for Low-Resistance Copper Contacts
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Solution Overview
Problem
Copper used in electronic devices' metallization layers and vias experiences high diffusion rates, leading to increased resistivity and semiconductor device failures, while barrier layers intended to prevent diffusion also increase contact resistance, and asymmetrical metal deposition at interfaces results in higher contact resistance due to heat transfer issues.
Innovation Solution
A layer of graphite or graphene is introduced at metal interfaces instead of barrier layers, reducing contact resistance and preventing heat transfer during metal deposition, thereby ensuring more symmetric deposition and improved electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If barrier layers are used to prevent copper diffusion, then copper diffusion is reduced, but contact resistance increases
Solution Approach 1:
The patent introduces a carbon-based intermediary layer (graphite or graphene) at the metal interface that acts as a mediator between the copper interconnect and the underlying metal. This carbon layer prevents copper diffusion into the underlying metal while maintaining low contact resistance, resolving the contradiction by providing a material that neither blocks electrons nor allows copper migration.
Solution Approach 2:
The patent uses composite material structures combining copper interconnects with carbon-based liner layers (graphite or graphene). This composite approach leverages the high electrical conductivity of copper while the carbon layer provides diffusion barrier properties, achieving both low contact resistance and copper diffusion prevention simultaneously.
2Reliability
If conventional barrier layers are deposited, then diffusion is prevented, but asymmetrical deposition occurs due to heat transfer, increasing contact resistance
Solution Approach 1:
The carbon-based layer serves as a thermal intermediary that moderates heat transfer during the deposition process. By positioning the carbon layer between the deposition source and the underlying metal, it creates more uniform thermal conditions that promote symmetrical deposition of the barrier layer, eliminating the asymmetry caused by direct heat transfer to the metal.
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 use of graphite or graphene layers significantly reduces contact resistance, enhances electrical performance, and prevents semiconductor device failures by minimizing copper diffusion and heat transfer asymmetries.
Implementation Method 1
preventing heat transfer during metal deposition
Implementation Method 2
reduces contact resistance
Implementation Method 3
minimizing copper diffusion
Data Source
AI summary
A layer of carbon (e.g., graphite or graphene) at a metal interface (e.g., between an MEOL interconnect and a gate contact or a source or drain region contact, between an MEOL contact plug and a BEOL metallization layer, and/or between BEOL conductive structures) is used to reduce contact resistance at the metal interface, which increases electrical performance of an electronic device. Additionally, in some implementations, the layer of carbon may help prevent heat transfer from a second metal to a first metal when the second metal is deposited over the first metal. This results in more symmetric deposition of the second metal, which reduces surface roughness and contact resistance at the metal interface. As an alternative, in some implementations, the layer of carbon is etched before deposition of the second metal in order to reduce contact resistance at the metal interface.