Three-Port SRAM Cell Layout for High-Density Memory Scaling
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Solution Overview
Problem
The semiconductor industry faces challenges in developing high-density, high-speed SRAM cells that can efficiently manage multiple ports for advanced memory applications, particularly in deep sub-micron technology, where traditional SRAM designs struggle with scaling and complexity.
Innovation Solution
The design of a three-port SRAM cell with a write port circuit and two read port circuits, utilizing fin-like field effect transistors (FinFETs) and gate-all-around field effect transistors (GAA FETs), with optimized metallization layers and interconnect structures to reduce RC delay and increase write margin, allowing for parallel operations and higher bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional SRAM designs are used, then manufacturing simplicity is maintained, but scaling to deep sub-micron technology becomes difficult and complexity increases
Solution Approach 1:
The SRAM cell is divided into distinct functional blocks including six transistors (two pull-up, two pass-gate, two pull-down) with clearly separated active structures. This segmentation allows each component to be optimized independently for deep sub-micron fabrication while maintaining overall cell functionality and reducing manufacturing complexity through modular design.
Solution Approach 2:
The patent employs multi-layer metallization structures with bit lines and word lines arranged in different metallization layers. This three-dimensional interconnect architecture reduces RC delay by minimizing wire lengths and optimizing signal paths, enabling better scaling performance without proportionally increasing processing complexity.
2Productivity
If more ports are added to SRAM for parallel operations, then bandwidth increases, but cell structure complexity increases
Solution Approach 1:
The SRAM cell is designed with three ports (one write port and two read ports) that share common transistors and interconnect structures. The pull-up and pull-down transistors serve multiple functions across different ports, allowing parallel read operations while reducing the total transistor count compared to fully independent port designs, thus achieving high bandwidth without proportional complexity increase.
Solution Approach 2:
Adjacent SRAM cells share common bit lines and word lines through optimized metallization layer routing. This merging of interconnect structures reduces the overall cell area and complexity while enabling parallel operations across multiple cells, achieving high productivity through资源共享 (resource sharing) rather than duplicating full cell structures for each port.
3Area of stationary object
If active structure regions are reduced for high density, then manufacturing precision challenges increase, but area efficiency improves
Solution Approach 1:
The patent implements asymmetric active structure widths where pull-up transistors have different active structure dimensions than pull-down transistors. This local quality optimization allows each transistor type to be sized appropriately for its specific function while maintaining compact overall cell area. The differentiated active structure design improves manufacturing precision by providing clear fabrication guidelines for each region rather than requiring uniform high-precision structures throughout.
Data Source
AI summary
Semiconductor devices are provided. A write port circuit is configured to perform a write function according to the write word line and the first and second write bit lines. The first read port circuit is configured to perform first read function according to the first read bit line and the first read word line. The second read port circuit is configured to perform second read function according to the second read bit line and the second read word line. The first and second gate structures of the first and second write pass-gate transistors are connected to a write word line landing pad that is connected to the write word line. The first and second read bit lines and the write word line landing pad extend in the first direction in a first metallization layer. The write word line extends in a second direction in a second metallization layer.