FinFET SRAM Cell Fin Gate Layout for Density
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving high SRAM density and manufacturing reliability due to the degradation of device performance and increased leakage in traditional SRAM cell structures with smaller semiconductor geometries, which requires innovative approaches for fin structure control in FinFETs.
Innovation Solution
The proposed solution involves a specific configuration and layout of FinFET SRAM cells with carefully controlled fin and gate pitches, combined with spacer lithography techniques using multiple masks to ensure precise alignment and uniformity of fin active lines and gate features, allowing for dense and reliable SRAM cell formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional planar transistor SRAM cell structure is used, then manufacturing process is simpler, but device performance degrades and leakage increases at smaller geometries
Solution Approach 1:
The patent transitions from planar transistors to FinFETs by adding a vertical dimension through fin structures. The fins extend vertically from the substrate, creating a three-dimensional transistor architecture that improves gate control over the channel while maintaining compatibility with standard CMOS fabrication processes.
Solution Approach 2:
The SRAM cell is divided into multiple fins within each transistor, with each fin acting as an independent current path. This segmentation allows better control of short-channel effects while maintaining scalability, as each fin can be independently optimized for performance and density.
2Quantity of substance
If fin structures are made thinner to achieve optimal short channel control, then SRAM density increases, but critical dimension uniformity becomes harder to control
Solution Approach 1:
Mandrel structures are introduced as intermediary elements that define the fin patterns. The mandrels serve as templates around which spacers are formed, and their dimensions and spacing are carefully controlled to ensure uniform fin critical dimensions. This intermediary step decouples the fin thickness control from direct lithography, improving manufacturability.
Solution Approach 2:
The patent employs spacer thickness as a critical parameter to control fin dimensions. By adjusting the spacer deposition thickness and etch parameters, precise fin critical dimensions can be achieved regardless of mandrel variations. This parameter control approach enables better CD uniformity through process optimization rather than relying solely on lithographic precision.
Data Source
AI summary
A semiconductor device includes first and second SRAM cells in a region of the semiconductor device. The first and second SRAM cells include FinFET transistors comprising gate features engaging fin active lines. Each of the first and second SRAM cells includes at least one gate feature overlapping with three or more fin active lines. Each of the first and second SRAM cells includes at least one fin active line over a first P-well adjacent one side of an N-well, and at least one fin active line over a second P-well adjacent another side of the N-well. The first and second SRAM cells share all the fin active lines over the first and second P-wells.