Balanced 8T Multi-Ported Memory Bitcell Layout for Smaller Arrays
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Solution Overview
Problem
Conventional memory arrays face inefficiencies due to layout transition region spacing and unbalanced use of P and N type transistors, leading to increased implementation footprint and reduced area efficiency, limiting scalability and performance.
Innovation Solution
The use of balanced, fully populated 8T bitcells with equal-sized PMOS and NMOS transistors eliminates transition regions and leverages future CFET technology, enabling multi-port functionality with reduced bitcell area and improved scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional memory arrays are used with unbalanced P-N transistor layouts, then implementation footprint is increased and area efficiency is reduced, but layout transition region spacing is maintained and manufacturing simplicity is preserved
Solution Approach 1:
The patent applies asymmetry by using unbalanced P-N transistor layouts where the diffusion regions are intentionally made asymmetric to eliminate transition regions. The P-type and N-type diffusion regions are configured with different geometries and positions to achieve direct adjacency, maximizing area utilization while maintaining manufacturability through the asymmetric design that eliminates the need for transition regions between balanced layouts
Solution Approach 2:
The patent merges the P-type and N-type diffusion regions directly adjacent to each other without transition regions, combining what were previously separate balanced layouts into a unified structure. This merging eliminates the spacing requirements between P-N regions and their transition areas, reducing overall bitcell area while maintaining ease of manufacture through continuous diffusion processes
2Productivity
If balanced P-N transistor layouts are used, then area efficiency is improved and transition regions are eliminated, but layout complexity increases and manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by creating specific localized diffusion regions with tailored geometries and positions. The P-type and N-type diffusion regions are designed with specific local characteristics including asymmetric shapes, different sizes, and strategic positioning to achieve direct adjacency. This local quality approach allows high area efficiency in the diffusion regions while managing manufacturing precision requirements through well-defined local structures rather than global symmetry constraints
Solution Approach 2:
The patent changes the geometric parameters of the diffusion regions, transitioning from symmetric balanced layouts to asymmetric configurations with specific area ratios, positions, and dimensions. By optimizing parameters such as diffusion region area, shape factors, and relative positioning, the patent achieves direct adjacency of P-N regions while maintaining manufacturability through well-specified parameter ranges that balance area efficiency with fabrication capabilities
3Adaptability or versatility
If transition regions are maintained between P-N diffusion regions, then manufacturing simplicity is preserved, but implementation footprint is increased and scalability is reduced
Solution Approach 1:
The patent extracts and eliminates the transition regions from the memory array layout, removing the spacing requirements that previously existed between P-type and N-type diffusion regions. By taking out these non-functional transition areas, the patent reduces the implementation footprint and enables better scalability, while the remaining diffusion regions are directly adjacent to each other without intermediate transition structures
Data Source
AI summary
A memory device includes at least one bitcell coupled to a local bitline. The at least one bitcell includes first, second, and third sets of a plurality of transistor devices. The first set is configured to form at least one write port. The at least one write port receives digital data. The second set of the plurality of transistor devices is configured as an inverter pair that stores the digital data. The third set of the plurality of transistor devices is configured to form at least one read port. The at least one read port is used to access the digital data from the inverter pair and output the digital data on the local bitline. The plurality of transistor devices consists of an equal number of P-channel transistor devices and N-channel transistor devices.