Memory Block Selection Using Select Transistor Threshold Voltage Differences

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Solution Overview

Problem

Existing memory devices with vertical memory cell strings face challenges in efficiently selecting and distinguishing between memory blocks due to shared source and drain select lines, leading to difficulties in performing program, read, and erase operations with high accuracy.

Innovation Solution

The implementation of select transistors with different threshold voltages in memory blocks, allowing for precise control of voltage combinations to selectively turn on or off transistors, enabling the electrical connection of specific memory blocks during operations by applying corresponding voltages to common source lines.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If select transistors with different threshold voltages are implemented in memory blocks, then the precision of selecting and distinguishing memory blocks is improved, but the device complexity increases

Engineering Contradiction:

Improveprecision of selecting memory blocksVSAvoidcomplexity of select transistor configuration

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies local quality by assigning different threshold voltage characteristics to select transistors based on their specific location and function within the memory device. First select transistors and second select transistors are configured with different threshold voltage ranges, allowing each transistor type to be optimized for its specific role in the memory cell string, thereby improving selection precision without requiring complete redesign of all transistors

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent segments the select transistor functionality into distinct groups with different threshold voltage characteristics. By dividing select transistors into first select transistors (with first threshold voltages) and second select transistors (with second threshold voltages), the system can independently control and optimize each segment, improving memory block discrimination while managing overall device complexity through modular configuration

Inventive Principle:

Principle #1Segmentation

2Reliability

If multiple select transistors with different threshold voltages are used, then the reliability of program, read, and erase operations is improved, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvereliability of memory operationsVSAvoidprecision of threshold voltage control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent implements parameter changes by establishing distinct threshold voltage ranges for different select transistor types. First select transistors are designed with threshold voltages in a first range, while second select transistors use threshold voltages in a second range. This parameter differentiation allows reliable operation across program, read, and erase cycles by ensuring sufficient voltage margins, while the use of standard fabrication techniques keeps manufacturing precision requirements within achievable limits

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10720212B2Memory device and method of operating the same

Publication Date: 2020.07.21 SK HYNIX INC

AI summary

A memory device with a plurality of memory block may include a plurality of memory cells constituting a memory blocks, and two or more select transistors coupled to the plurality of memory cells constituting the memory block and configured to select the memory block, the two or more select transistors having different threshold voltages from one another.