Semiconductor Memory Device Source Select Transistor Programming
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Solution Overview
Problem
Existing semiconductor memory devices face challenges in improving the reliability of read operations due to the limitations in coding source select transistors across different memory strings.
Innovation Solution
The semiconductor memory device employs a method where source select transistors in different memory strings are programmed to distinct states, allowing for improved coding data values and selective activation of string groups during read operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If source select transistors are uniformly programmed across all memory strings, then device complexity is reduced, but read operation reliability deteriorates due to inability to selectively activate string groups
Solution Approach 1:
The patent divides memory strings into multiple string groups (first string group and second string group) based on the programming state of source select transistors. Each string group has distinct coding data values, enabling selective activation during read operations. This segmentation resolves the contradiction by organizing transistors into functional groups that improve reliability while maintaining manageable complexity through systematic classification.
Solution Approach 2:
Different source select transistors are programmed to different states (first state for first string group, second state for second string group) to create local differentiation. This local quality variation allows specific string groups to be activated based on read requirements, improving read operation reliability without requiring complete reprogramming of all transistors, thus balancing reliability improvement with complexity management.
2Loss of information
If all source select transistors are programmed to the same state, then manufacturing process is simplified, but coding data value differentiation is lost
Solution Approach 1:
The patent segments source select transistors into different programming groups corresponding to different string groups. First source select transistors are programmed to a first state while second source select transistors are programmed to a second state, creating differentiated coding data values. This segmentation preserves information differentiation by assigning distinct states to different transistor groups, while maintaining manufacturing ease through a systematic, repeatable programming process.
Solution Approach 2:
The patent changes the programming state parameter of source select transistors based on their group assignment. Transistors in different string groups are programmed to different states (first state vs. second state), creating parameter variation that enables coding data value differentiation. This parameter change approach maintains ease of manufacture by using controlled, discrete state assignments rather than continuous variation.
3Reliability
If multiple string groups are activated simultaneously, then data retrieval speed is improved, but reliability deteriorates due to inability to selectively access specific groups
Solution Approach 1:
The patent implements dynamic selection of string groups for activation based on read operation requirements. By programming source select transistors to different states, the system can dynamically activate only the necessary string groups (first string group, second string group, or both) depending on the data retrieval needs. This dynamic approach improves reliability through selective access while maintaining productivity by enabling parallel activation when required.
Data Source
AI summary
Provided herein is a semiconductor memory device and a method of operating the same. The semiconductor memory device includes a first string group including at least one first memory string and a second string group including at least one second memory string, each string connected in parallel between the bit line and the source line, wherein the at least one first memory string and the at least one second memory string each include at least one down source select transistor, at least one first up source select transistor, and at least one second up source select transistor, and the at least one first up source select transistor of the at least one first memory string is programmed to a first state, and the at least one first up source select transistor of the at least one second memory string is programmed to a second state different from the first state.