Graphene Etch-Stop Interconnects for Low-Resistance Wide Lines
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Solution Overview
Problem
Current semiconductor fabrication processes face challenges in forming reliable interconnects, particularly with copper, as the resistance increases significantly when trench widths are 12 nm or smaller, and the removal of conductors like cobalt from wide trenches is not controllable using existing etching methods.
Innovation Solution
The method involves forming a graphene layer as an etch stop and using it to selectively remove the first conductor from wide trenches, allowing for the deposition of a second conductor with reduced line resistance, while minimizing surface scattering of electrons through the interface with the graphene.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If copper is used in narrow trenches (12 nm or smaller), then interconnect density is improved, but resistance increases significantly
Solution Approach 1:
The patent applies different conductor materials to different trench width regions: cobalt is used in narrow trenches (12 nm or smaller) where it maintains low resistance, while copper is used in wider trenches where it provides lower resistance and cost benefits. This local differentiation resolves the contradiction by matching material properties to specific geometric constraints.
Solution Approach 2:
The patent segments the interconnect structure into narrow lines and wide lines, with narrow lines filled with cobalt and wide lines filled with copper. This segmentation allows each region to use the most appropriate material for its specific dimensions, thereby maintaining low resistance across all interconnect widths while achieving high density.
2Ease of manufacture
If existing etching methods are used to remove cobalt from wide trenches, then conductor removal is attempted, but the process is not controllable
Solution Approach 1:
The patent introduces a graphene layer as an intermediary etch-stop layer between the cobalt conductor and the underlying substrate. During etching, the graphene layer protects the substrate while allowing controlled removal of cobalt from wide trenches. This intermediary enables precise control over the etching process, preventing over-etching and damage to the substrate.
Solution Approach 2:
The graphene layer is deposited on the substrate before cobalt deposition, creating a pre-prepared etch-stop structure. This preliminary action ensures that when cobalt needs to be removed from wide trenches, the etching process can be precisely controlled by the pre-existing graphene barrier, eliminating the controllability issues of direct etching methods.
3Device complexity
If conventional interconnect structures are used, then fabrication is simpler, but surface scattering increases resistance
Solution Approach 1:
The patent creates a composite interconnect structure consisting of multiple layers: substrate, graphene layer, cobalt layer in narrow trenches, and copper layer in wide trenches. This composite structure combines the advantages of different materials (graphene's low scattering, cobalt's stability in narrow dimensions, copper's low resistance in wider dimensions) to achieve overall reduced resistance while maintaining manageable fabrication complexity through standardized deposition and etching processes.
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 reduced line resistance for wide lines by utilizing a low resistivity conductor and minimizing surface scattering, enhancing electron mobility and interconnect performance.
Implementation Method 1
The graphene layer acts as an etch stop for the etching process
Implementation Method 2
minimizing surface scattering of electrons through the interface with the graphene
Data Source
AI summary
A semiconductor fabrication method that uses a graphene etch stop is disclosed. The method comprises forming a first set of trenches and a second set of trenches in a substrate. The first set of trenches are narrower than the second set of trenches. The method further comprises forming a graphene layer in the first and second sets of trenches. The method further comprises depositing a first conductor in the first and second sets of trenches. The method further comprises removing the first conductor from the second set of trenches using an etching process. The graphene layer acts as an etch stop for the etching process. The method further comprises depositing a second conductor in the second set of trenches. The second conductor is different than the first conductor.