Vertical Semiconductor Strings With Segmented Source Lines
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Solution Overview
Problem
Three-dimensional (3D) semiconductor devices face reliability issues due to changes in threshold voltages of memory cells adjacent to the source line during program and read operations, which affect the overall performance and durability of the devices.
Innovation Solution
A semiconductor device with vertical strings that share bit lines or source lines, featuring a control circuit, page buffers, and a selection switch unit to manage voltages and data transfer, and a method that includes sequential programming, reading, and erasing operations to optimize voltage application and reduce resistance within the strings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If strings are formed in vertical direction to increase degree of integration, then device capacity is improved, but threshold voltage stability deteriorates due to resistance around source line
Solution Approach 1:
The source line is divided into multiple independent source lines (first source line and second source line). Each string is connected to a specific source line, allowing independent voltage control. This segmentation prevents resistance changes in one source line from affecting threshold voltages of memory cells connected to other source lines, thereby maintaining threshold voltage stability while supporting vertical string configuration for high integration.
Solution Approach 2:
Different source lines are assigned to different strings or string groups, enabling localized voltage control. By applying voltages selectively to specific source lines rather than uniformly to all strings, the patent optimizes program and read operations for specific regions while minimizing interference and resistance effects on other regions, thus maintaining threshold voltage stability in vertically integrated structures.
2Device complexity
If multiple strings share common bit lines or source lines, then device complexity is reduced, but threshold voltage control precision deteriorates
Solution Approach 1:
The patent segments the source line into multiple independent source lines, with each string connected to a specific source line. This segmentation allows independent voltage control for each string while maintaining a relatively simple overall architecture. The segmentation enables precise threshold voltage control for each memory cell without requiring complex routing, as each string has its dedicated voltage supply path.
Solution Approach 2:
Multiple source lines are designed with identical structures and functions, allowing them to be manufactured using the same processes. This universality simplifies manufacturing while enabling precise independent control of threshold voltages across different strings. Each source line can serve multiple purposes: providing voltage during program operations, serving as a reference during read operations, and being independently controlled to prevent interference.
Data Source
AI summary
A semiconductor device includes first memory blocks arranged in a longitudinal direction, and including a plurality of strings, wherein the strings are formed along a vertical direction, and the strings adjacent to each other share bit lines or source lines with each other, each string including a drain selection transistor coupled to an odd drain selection line or an even drain selection line, memory cells coupled to word lines, and a source selection transistor coupled to an odd source selection line or an even source selection line, page buffers suitable for storing data, a selection switch unit suitable for transferring the data stored in the page buffers or various voltages supplied from an external source to the bit lines and the source lines; and a control circuit suitable for controlling the page buffers and the selection switch unit.