Dual-Port SRAM Cell With Segmented Gate Structure
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Solution Overview
Problem
The U-shaped gate structure in deep sub-micron integrated circuit technology for SRAM devices leads to pull-down device variation, integration concerns, and critical dimension uniformity issues, affecting SRAM cell stability and scaling capability.
Innovation Solution
A dual-port SRAM cell design incorporating fin field-effect transistors (FinFETs) with a balanced configuration of pull-down and pass-gate devices, along with long gate contact features and asymmetric gate contact structures, to address the issues of device variation and packing density, enhancing stability and scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If U-shaped gate structure is employed to achieve high packing density, then area utilization is improved, but critical dimension uniformity deteriorates causing necking and leakage problems
Solution Approach 1:
The gate structure is segmented into multiple straight sections rather than a continuous U-shaped curve. The gate electrode is divided into first, second, and third sections that are substantially straight and separated by gaps, eliminating the rounding issues inherent in U-shaped gates while maintaining compact area utilization.
Solution Approach 2:
The gate structure transitions from symmetric U-shape to asymmetric straight-line configuration. The first and third gate sections are positioned at different locations relative to the second gate section, creating an asymmetric layout that improves critical dimension control while achieving comparable or better packing density.
2Area of stationary object
If U-shaped gate structure is used to increase packing density, then area efficiency is improved, but device reliability deteriorates due to pull-down device variation
Solution Approach 1:
The gate electrode is segmented into multiple straight sections with gaps between them. This segmentation eliminates the stress concentration and manufacturing variability associated with U-shaped gates, thereby improving pull-down device matching and overall device reliability while maintaining high packing density.
3Area of stationary object
If feature size is decreased to increase packing density, then area efficiency is improved, but manufacturing precision deteriorates due to necking and leakage
Solution Approach 1:
By segmenting the gate into straight sections rather than using a continuous U-shaped curve, the minimum feature size requirements are relaxed. The straight sections can be manufactured with better dimensional control at smaller scales, enabling continued scaling while maintaining manufacturing precision.
4Speed
If U-shaped gate structure is implemented to achieve high speed, then access speed is improved, but device complexity increases due to integration concerns
Solution Approach 1:
The segmented straight gate structure simplifies the fabrication process compared to U-shaped gates. The straight sections can be formed using standard lithography and etching processes without requiring complex curved pattern alignment, thereby reducing integration complexity while maintaining high access speed through optimized device geometry.
Data Source
AI summary
The present disclosure provides a static random access memory (SRAM) cell. The SRAM cell includes first and second inverters cross-coupled for data storage, each inverter including at least one pull-up device and at least two pull-down devices; at least four pass gate devices configured with the two cross-coupled inverters; at least two ports coupled with the at least four pass-gate devices for reading and writing; a first contact feature contacting first two pull-down devices (PD-11 and PD-12) of the first inverter; and a second contact feature contacting second two pull-down devices (PD-21 and PD-22) of the second inerter.