First Metal Layer Local Interconnect for Reduced Cell Height
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Solution Overview
Problem
Existing semiconductor technologies face challenges in reducing the height of standard cells while maintaining effective local interconnects, often requiring additional photolithography masks that increase process risk and fabrication costs, especially when using extreme ultraviolet photolithography.
Innovation Solution
A method is introduced to form metal lines in the first metal layer over front-end-of-line structures, where the second metal line serves as both a metal line and a local interconnect by extending a branch portion perpendicular to the main direction, electrically connecting the gate and source/drain contact vias without the need for additional photolithography masks below the first metal layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional photolithography masks are used to form local interconnect below the first metal layer, then local interconnect can be formed, but process risk and fabrication cost increase
Solution Approach 1:
The patent merges the local interconnect formation with the first metal layer by forming both the metal line and local interconnect in the same layer simultaneously. This is achieved by patterning the first metal layer to create metal lines with discontinuities, and filling those discontinuities with conductive material to form local interconnects, eliminating the need for separate mask processes below the first metal layer.
Solution Approach 2:
The first metal layer serves dual functions: it provides both the metal interconnect lines and the local interconnect structures. By designing the metal lines with intentional discontinuities and filling those gaps, the same layer performs both routing and local connection functions, reducing overall process complexity.
2Length of stationary object
If the number of metal lines is reduced to lower cell height, then cell height is reduced, but forming local interconnect becomes more difficult
Solution Approach 1:
The patent transitions from vertical stacking of multiple metal layers to horizontal integration within the first metal layer. By forming local interconnects in the same layer as the metal lines through discontinuity and filling, the solution adds functional complexity in the planar dimension rather than requiring additional vertical layers, thus maintaining low cell height.
Solution Approach 2:
The metal lines are intentionally designed with segments or discontinuities rather than continuous traces. These segmented metal lines create openings that are subsequently filled to form local interconnects, allowing the first metal layer to provide both routing and connection functions without requiring additional metal layers.
3Reliability
If additional photolithography masks are used, then local interconnect can be formed, but fabrication cost increases
Solution Approach 1:
The patent combines multiple functions into a single process step. The first metal layer formation process simultaneously creates both the metal interconnect lines and the local interconnect structures, eliminating the need for additional photolithography masks and reducing fabrication costs.
Solution Approach 2:
The first metal layer structure is designed to be self-sufficient by incorporating both metal lines and local interconnects within the same layer. The discontinuities in the metal lines automatically define the locations for local interconnect formation, eliminating the need for external guidance from additional masks.
Data Source
AI summary
Semiconductor structures and methods are provided. A semiconductor structure according to the present disclosure includes a first metal line extending along a first direction, a second metal line lengthwise aligned with and spaced apart from the first metal line, and a third metal line extending along the first direction. The third metal line includes a branch extending along a second direction perpendicular to the first direction and the branch partially extends between the first metal line and the second metal line.