FinFET Dummy Gate Spacing for Short Channel Effect Reduction
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Solution Overview
Problem
Current semiconductor devices, such as FinFETs, face challenges in optimizing the spacing between dummy and normal gates to enhance current driving capability and reduce short channel effects, while maintaining effective gate structures.
Innovation Solution
The semiconductor device incorporates a unique arrangement of active fins with dummy and normal gates, where the spacing between dummy gates is smaller than between normal gates, and the use of mandrel spacers to form gate patterns through an etching process, allowing for efficient fabrication and improved transistor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the spacing between dummy gates is reduced to improve fabrication efficiency and reduce short channel effects, then manufacturing precision and device performance improve, but it becomes difficult to maintain adequate spacing for gate formation processes
Solution Approach 1:
The gate structure is segmented into normal gates (for active fins) and dummy gates (for inactive regions), with different spacing requirements. This segmentation allows optimized spacing for each type: tighter spacing for dummy gates to reduce short channel effects while maintaining adequate spacing for normal gates to ensure proper gate formation and electrical isolation.
Solution Approach 2:
Different spacing configurations are applied locally to different regions: dummy gates have smaller spacing between them (first spacing) compared to the spacing between normal gates (second spacing). This local differentiation optimizes each region's performance - tighter spacing in dummy gate regions reduces short channel effects, while larger spacing in normal gate regions ensures proper electrical isolation and gate formation.
2Reliability
If FinFETs are used to reduce short channel effects and increase current driving capability, then device performance improves, but the gate length cannot be increased to further enhance current driving capability
Solution Approach 1:
The invention transitions from planar gate structures to three-dimensional FinFET structures, where the gate wraps around the fin in a U-shape configuration. This dimensional change allows the gate to control the channel from multiple directions (top and sidewalls), effectively reducing short channel effects without increasing the linear gate length. The gate length remains constrained while achieving better electrostatic control through the vertical fin structure.
3Reliability
If dummy gates are added to cover end portions of active fins, then short channel effects are reduced, but the device structure and fabrication process become more complex
Solution Approach 1:
The dummy gates serve multiple functions: they cover the end portions of active fins to reduce short channel effects, they provide a template for forming mandrel spacers that define normal gate positions, and they maintain structural symmetry in the fabrication process. By making dummy gates multi-functional, the added structural complexity is justified by multiple performance and process benefits.
Solution Approach 2:
Dummy gates are formed in advance during the gate patterning process before normal gates are defined. They serve as preliminary structures that guide subsequent fabrication steps, particularly in forming mandrel spacers that will define the positions of normal gates. This preliminary action simplifies the overall fabrication sequence by establishing reference structures early in the process.
Data Source
AI summary
A semiconductor device is provided. A substrate includes first and second active fins disposed in a row along a first direction. The first and second active fins are spaced apart from each other. A first dummy gate and a second dummy gate are disposed on the substrate and are extended in a second direction intersecting the first direction. The first dummy gate covers an end portion of the first active fin. The second dummy gate covers an end portion of the second active fin facing the end portion of the first active fin. A first dummy spacer is disposed on a sidewall of the first dummy gate. A second dummy spacer is disposed on a sidewall of the second dummy gate. The sidewall of the second dummy gate faces the sidewall of the first dummy gate. The first dummy spacer is in contact with the second dummy spacer.