SRAM Latch-Up Prevention via Interlaced Well Segmentation
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Solution Overview
Problem
Static random access memory (SRAM) structures face issues with latch-up and noise interference due to leakage currents from adjacent well regions, which can lead to permanent damage and affect the reliability and performance of integrated circuits.
Innovation Solution
The SRAM structure incorporates a ladder-shaped or comb-shaped arrangement of P-well and N-well regions with strategically placed pick-up regions to form guard rings that prevent latch-up and reduce noise interference, using interlaced well regions and varying the number and placement of pick-up regions to manage leakage currents effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If well regions are placed adjacent to each other in SRAM structure, then device integration is achieved, but latch-up and noise interference occur due to leakage currents
Solution Approach 1:
The well regions are segmented into alternating P-well and N-well regions arranged in a ladder-shaped or comb-shaped configuration. This segmentation creates isolated zones that prevent continuous leakage current paths between adjacent wells, thereby preventing latch-up while maintaining high device integration.
Solution Approach 2:
Pick-up regions are introduced as intermediary structures between adjacent P-well and N-well regions. These pick-up regions act as mediators that intercept and redirect leakage currents, preventing them from causing latch-up or noise interference while allowing the well regions to remain closely spaced for high integration.
2Productivity
If well regions are placed adjacent to each other in SRAM structure, then device integration is achieved, but noise interference occurs due to leakage currents
Solution Approach 1:
The alternating P-well and N-well regions are segmented into discrete units separated by pick-up regions. This segmentation isolates noise sources in each well region, preventing noise propagation to adjacent regions while maintaining compact integration for high productivity.
Solution Approach 2:
Pick-up regions serve as intermediary noise barriers between adjacent well regions. They intercept leakage currents that would otherwise generate noise signals, thereby reducing noise interference while allowing the well regions to be closely spaced for high device integration.
3Reliability
If pick-up regions are added to prevent latch-up and reduce noise, then reliability and noise management improve, but device complexity increases
Solution Approach 1:
The pick-up regions are merged with the ladder-shaped or comb-shaped well region configuration, forming an integrated structure where pick-up regions are strategically positioned at intersections or along the edges of adjacent wells. This merging approach prevents latch-up and reduces noise without requiring completely separate additional structures, thereby limiting the increase in device complexity.
Solution Approach 2:
The pick-up regions perform multiple functions simultaneously: they prevent latch-up by intercepting leakage currents, reduce noise interference by isolating adjacent wells, and maintain structural integrity of the well regions. This multi-functionality reduces the need for separate dedicated structures, thereby limiting complexity increase while achieving improved reliability and noise management.
Data Source
AI summary
An SRAM structure is provided. The SRAM structure includes a plurality of first well regions with a first doping type, a second well region with a second doping type, a plurality of first well pick-up regions, a plurality of second well pick-up regions and a plurality of memory cells. The first well regions are formed in a semiconductor substrate. The second well region is formed in the semiconductor substrate. The first well pick-up regions are formed in the first well regions. The second well pick-up regions are formed in the second well region. Each of the memory cells is disposed on two adjacent first well regions and a portion of the second well region between the two adjacent first well regions. Each of the first well pick-up regions is disposed between two adjacent second well pick-up regions.