Semiconductor Memory Local Sink Switch Disturbance Prevention
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Solution Overview
Problem
Current semiconductor memory devices face challenges in preventing write and read disturbances due to floating local bit lines and source lines, which can lead to noise interference and disturbances in memory cell operations.
Innovation Solution
The semiconductor memory device incorporates a local sink switch with sink select transistors that connect local bit lines and source lines to a global source line, ensuring they are set to a predetermined voltage, thereby preventing disturbances without the need for additional discharge circuits, which reduces circuit complexity and area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional discharge circuits are added to prevent write and read disturbances, then reliability is improved, but device complexity increases
Solution Approach 1:
The local sink switch is designed to perform multiple functions: it acts as a discharge circuit to prevent write disturbances, provides a predetermined voltage during read operations to prevent read disturbances, and integrates with existing circuit components. This multi-functionality eliminates the need for separate discharge circuits while maintaining reliability.
Solution Approach 2:
The patent combines the discharge function with the read operation control function into a single local sink switch circuit. By merging these functions, the circuit complexity is reduced compared to having separate discharge circuits and read control circuits, while still achieving both disturbance prevention goals.
2Reliability
If additional discharge circuits are added to prevent write and read disturbances, then reliability is improved, but area increases
Solution Approach 1:
The local sink switch serves multiple purposes within the same physical space: discharging local bit lines during write operations, providing predetermined voltage during read operations, and preventing both write and read disturbances. This eliminates the need for additional dedicated discharge circuit area.
Solution Approach 2:
By integrating the discharge function into the existing local sink switch structure that is already present in the memory array, the patent avoids adding separate discharge circuit components that would increase area. The same transistors and connections serve dual purposes.
3Device complexity
If local bit lines and source lines are left floating, then device complexity is reduced, but harmful factors increase due to noise interference and disturbances
Solution Approach 1:
The local sink switch is activated in advance before write and read operations to ensure local bit lines and source lines are properly discharged or held at predetermined voltage levels. This preliminary action prevents noise accumulation and disturbances before they can affect memory cell operations.
Solution Approach 2:
The local sink switch acts as an intermediary component between the memory cells and the global bit lines/source lines. It mediates the electrical connections by providing discharge paths and voltage control, thereby eliminating the harmful effects of floating lines without requiring fundamental changes to the memory cell structure.
Data Source
AI summary
According to one embodiment, a semiconductor memory device includes: a first bit line; a first source line; a first word line; a first control line; a first memory cell comprising a first variable resistance element and a first transistor, the first transistor including a gate coupled to the first word line, the first memory cell including one end coupled to the first bit line and another end coupled to the first source line; a second transistor including one end coupled to the first bit line; and a third transistor including a gate coupled to the first control line, one end coupled to the first bit line, and another end coupled to the first source line.