SRAM Layout With Segmented Bitlines for Lower RC Delay
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Solution Overview
Problem
The existing SRAM designs face performance degradation due to bitline resistive-capacitive (RC) delay, which increases with the number of memory cells coupled to bitlines, leading to slower read and write operations.
Innovation Solution
The SRAM layout is optimized by reducing bitline loading to 4, 8, or 16 memory cells per bitline, using gate-all-around field effect transistors (GAA FETs) and implementing a single well pick-up region on the near end of the memory cell region, along with power supply and bitline jumper routing regions, to minimize parasitic effects and congestion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of memory cells coupled to bitlines is increased to maximize storage capacity, then storage capacity is improved, but bitline RC delay increases leading to slower read and write operations
Solution Approach 1:
The bitline loading is segmented into smaller groups of 4, 8, or 16 memory cells per bitline, rather than coupling all memory cells to each bitline. This segmentation reduces the RC delay on each bitline while maintaining overall storage capacity through increased bitline count and optimized memory array architecture.
2Stability of the object's composition
If traditional SRAM layout with multiple well pick-up regions is used, then well potential stability is improved, but layout complexity and parasitic effects increase
Solution Approach 1:
The design extracts and eliminates the need for multiple well pick-up regions by using a single well pick-up region combined with optimized memory cell placement and bitline loading. This reduction in the number of well pick-up regions simplifies the layout while maintaining well potential stability through alternative design approaches.
Solution Approach 2:
The patent applies local quality optimization by concentrating well pick-up functionality in a single strategically placed region and compensating for potential instability through localized field effect transistor design and bitline loading optimization, rather than distributing multiple well pick-up regions throughout the layout.
3Speed
If bitline loading is reduced to 4, 8, or 16 memory cells per bitline, then bitline RC delay is reduced improving speed, but more bitlines are required increasing layout area
Solution Approach 1:
The patent addresses the area increase from reduced bitline loading by optimizing the spatial arrangement of bitlines and memory cells in multiple dimensions. The memory array is organized to efficiently pack cells with reduced bitline loading, and bitlines are routed through optimized pathways that minimize area occupation while maintaining the reduced loading configuration.
Data Source
AI summary
The present disclosure describes a method for memory cell placement. The method can include placing a memory cell region in a layout area and placing a well pick-up region and a first power supply routing region along a first side of the memory cell region. The method also includes placing a second power supply routing region and a bitline jumper routing region along a second side of the memory cell region, where the second side is on an opposite side to that of the first side. The method further includes placing a device region along the second side of the memory cell region, where the bitline jumper routing region is between the second power supply routing region and the device region.