SRAM Bit Cell With Continuous PFET Active Regions
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Solution Overview
Problem
The existing fabrication of semiconductor devices, particularly SRAM memory cells, faces challenges in scaling and manufacturing complexity due to the precise formation and positioning of small PFET active regions, which can result in irregular configurations and impact performance.
Innovation Solution
The introduction of novel bit cell configurations with extension field effect transistors that are electrically coupled to inverter circuits, allowing for the formation of continuous PFET active regions across the bit cell, simplifying the patterning process and improving scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional 6T SRAM cell design with isolated PFET active regions is used, then memory function is achieved, but manufacturing precision and device complexity increase due to precise formation and positioning requirements
Solution Approach 1:
The patent merges the PFET active regions into a continuous shared structure that serves multiple bit cells, eliminating the need for isolated PFET regions in each cell. This continuous PFET active region is shared by adjacent bit cells, reducing the number of discrete components and simplifying the patterning process while maintaining the required memory functionality.
Solution Approach 2:
The continuous PFET active region serves multiple functions: it acts as the active region for PFET transistors in multiple adjacent bit cells simultaneously, providing a universal structure that reduces manufacturing steps. The shared PFET active region is used by different bit cells for their respective PFET devices, eliminating redundant patterning operations.
2Ease of manufacture
If continuous PFET active regions are formed, then manufacturing process is simplified and scalability improved, but adjacent cell isolation may be affected
Solution Approach 1:
The patent segments the continuous PFET active region into functionally distinct zones for adjacent bit cells using NFET active regions and isolation structures. While the PFET active region itself is continuous, the NFET active regions are positioned to create functional segmentation, ensuring that each bit cell operates independently. This segmentation is achieved through the strategic placement of NFET devices and their associated active regions that act as natural barriers between adjacent cells.
Solution Approach 2:
The NFET active regions and isolation structures serve as intermediary elements between adjacent bit cells that share the continuous PFET active region. These intermediary structures ensure proper electrical isolation and signal separation between cells while allowing the PFET active region to remain continuous, thus maintaining both ease of manufacture and cell isolation reliability.
Data Source
AI summary
Disclosed is an illustrative bit cell that includes a first inverter circuit that includes a first input node and a first output node and a second inverter circuit that includes a second input node and a second output node, wherein the first output node is coupled to the second input node and the second output node is coupled to the first input node. The bit cell also includes a first extension field effect transistor that includes a first gate structure, a first cell-internal S/D region and a first cell boundary node S/D region, wherein first cell-internal S/D region electrically terminates within the cell boundary. The first gate structure is electrically coupled to one of the first or second input nodes and it is also shorted to the first cell-internal S/D region.