5T SRAM Memory Cell Array with Shared Pull-Down Network
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Solution Overview
Problem
The semiconductor industry seeks alternatives to traditional 6-transistor SRAM designs for memory macros to achieve denser and faster integrated circuits, as current designs are limited by the size and efficiency of memory cells.
Innovation Solution
The implementation of a 5-transistor SRAM memory cell array with a non-rectangular tile layout design, which alternates sets of tiles to create smaller standard cells, allowing for more efficient use of space and improved performance by reducing the number of transistors while maintaining memory capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If traditional 6-transistor SRAM memory cells are used, then memory capacity and reliability are maintained, but the memory cell area is larger and device density is lower
Solution Approach 1:
The patent extracts one transistor from the traditional 6-transistor SRAM memory cell configuration, reducing the transistor count to five. This is achieved by sharing a common pull-down network between adjacent memory cells, thereby removing the need for one dedicated pull-down transistor per cell while maintaining the essential memory functionality and reliability.
Solution Approach 2:
The patent merges the pull-down networks of adjacent memory cells by implementing a shared common pull-down transistor. This consolidation allows multiple memory cells to share a single transistor instance, reducing the overall transistor count per cell area while maintaining proper memory operation and data retention characteristics.
2Quantity of substance
If 6-transistor SRAM memory cells are used, then memory functionality is ensured, but the number of transistors per unit area increases reducing device density
Solution Approach 1:
The patent removes one transistor from each memory cell by implementing a shared common pull-down network. This extraction reduces the transistor quantity from six to five per memory cell, directly increasing device density while preserving essential memory functionality through the shared transistor architecture.
Solution Approach 2:
The common pull-down transistor serves multiple memory cells simultaneously, performing the pull-down function for adjacent cells that would otherwise require separate dedicated transistors. This multi-functional approach reduces the total transistor count while maintaining proper memory operation across the array.
3Area of stationary object
If non-rectangular tile layout is implemented, then space utilization is improved and memory capacity increases, but layout complexity increases
Solution Approach 1:
The patent employs non-rectangular tile layouts with asymmetric arrangements of memory cells and shared transistors. This asymmetric design optimizes space utilization by eliminating wasted layout space while the systematic sharing pattern maintains manufacturing feasibility and layout regularity at higher levels.
Solution Approach 2:
The memory array is segmented into multiple tiles with standardized non-rectangular patterns. This segmentation allows the complex layout to be broken down into repeatable units, reducing overall layout complexity while achieving high space utilization through efficient packing of the asymmetric tile structures.
Data Source
AI summary
A memory cell array includes a first and second memory cell, a first and second word line and a first bit line. The first memory cell is in a first row in a first direction. The second memory cell is in a second row in the first direction, and is separated from the first memory cell in a second direction. The first word line extends in the first direction and is coupled to the first memory cell. The second word line extends in the first direction and is coupled to the second memory cell. The first bit line extends in the second direction and is coupled to the first and second memory cell. The first memory cell corresponds to a five transistor memory cell. The first memory cell includes a first active region having a first length, and a second active region having a second length.