Single-Port SRAM Bit Cell Layout for Faster Read-Write Scaling
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Solution Overview
Problem
The increasing demand for faster read and write speeds in Static Random Access Memory (SRAM) cells, particularly with the down-scaling of already small SRAM cells, poses challenges in achieving these performance requirements due to the complexity of processing and manufacturing in the semiconductor industry.
Innovation Solution
The design of a single-port SRAM bit cell incorporating FinFETs and gate-all-around (GAA) transistors, with a specific configuration of pass-gate, pull-up, pull-down, and isolation transistors, and a unique metal and via layer structure to enhance device stability and speed, allowing for improved chip performance and lower power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If SRAM cells are down-scaled to increase functional density, then the number of interconnected devices per chip area increases, but the read speed and write speed become difficult to achieve
Solution Approach 1:
The patent transitions from planar transistor structures to three-dimensional FinFET structures with vertical fins extending from the substrate. This vertical dimension allows for increased functional density without proportionally increasing area, while the three-dimensional structure provides better gate control over the channel, enabling faster switching speeds despite the down-scaling of individual cell dimensions.
Solution Approach 2:
The patent changes key parameters including the use of high-k dielectric materials with increased dielectric constant, modified gate lengths, adjusted fin heights, and optimized spacing between fins and gates. These parameter changes enable the transistors to achieve higher transconductance and faster switching speeds while maintaining compatibility with scaled-down geometries.
2Ease of manufacture
If traditional SRAM cell designs are used, then manufacturing processes are simpler, but device stability and matching are insufficient for high-speed operation
Solution Approach 1:
The patent divides the transistor gate into multiple segments including gate electrodes, gate spacers, and gate dielectric layers arranged in a FinFET configuration. This segmentation allows for independent optimization of each component to improve device stability and matching while maintaining manufacturability through established semiconductor fabrication processes.
Solution Approach 2:
The patent applies different material properties and structural characteristics to different regions of the transistor device. High-k dielectric materials are used in specific gate regions to enhance capacitance and switching speed, while maintaining standard materials in other areas to ensure compatibility with existing manufacturing processes. The FinFET structure provides localized control over the channel region to improve device matching.
3Area of moving object
If SRAM cells are made smaller to increase density, then functional density increases, but power supply requirements increase
Solution Approach 1:
The vertical FinFET structure provides better electrostatic control over the channel, reducing leakage current and allowing for lower operating voltages. The three-dimensional gate wrapping around the fin channel enables more effective carrier modulation, improving switching efficiency and reducing the power required for signal transitions while maintaining high functional density.
Solution Approach 2:
The patent employs composite material structures including high-k dielectric layers combined with metal gates, and multi-layer metal interconnect structures. These composite materials enable better electrical performance with reduced resistance and capacitance, allowing for lower power consumption while maintaining the scaled-down device dimensions for high density.
Data Source
AI summary
Semiconductor devices are provided. A memory cell includes a first pull-down transistor, a second pull-down transistor, a first pass-gate transistor, and a second pass-gate transistor formed over a P-type well region, and a first pull-up transistor, a second pull-up transistor, a first isolation transistor, and a second isolation transistor formed over an N-type well region. The first and second pull-down transistors and the first and second pass-gate transistors share a first active region. The first and second pull-up transistors and the first and second isolation transistors share a second active region. The gates of the first and second isolation transistors are electrically connected to a VDD line. The gates of the first and second pass-gate transistors are electrically connected to a WL landing pad. The sources of the first and second pass-gate transistors are electrically connected to the first bit line and the second bit line, respectively.