Nonvolatile Memory Selection Transistor Voltage Programming
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Solution Overview
Problem
Current nonvolatile memory devices face challenges in efficiently programming and verifying the threshold voltages of selection transistors in three-dimensional memory cell arrays, which affects the reliability of programming, reading, and erasing operations.
Innovation Solution
The proposed method involves a specific voltage programming sequence for string selection transistors and ground selection transistors, including Fowler-Nordheim tunneling and hot carrier injection mechanisms, to accurately set and verify threshold voltages, ensuring reliable operation of memory cells in a three-dimensional memory device structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a three-dimensional array structure is used to increase integration density, then the degree of integration is improved, but the complexity of programming and verifying selection transistor threshold voltages increases
Solution Approach 1:
The memory device is divided into multiple cell strings, each with independently controllable first and second selection transistors. This segmentation allows selective programming of specific transistors within the three-dimensional array by applying voltages to specific bit lines and selection lines, managing the complexity of high-density integration.
Solution Approach 2:
The method performs preliminary programming of the first selection transistor before programming the memory cells. This preliminary action ensures that the selection transistor is properly configured to enable subsequent memory cell programming, verifying threshold voltages in advance to prevent programming errors in the high-density structure.
2Quantity of substance
If multiple selection transistors are stacked vertically in cell strings, then the integration density is improved, but the precision of threshold voltage control deteriorates
Solution Approach 1:
Different voltage levels are applied to different parts of the cell string structure. The first selection transistor receives a first voltage on its bit line while the second selection transistor receives a second voltage, allowing independent and precise control of each transistor's threshold voltage despite their vertical stacking in the three-dimensional structure.
Solution Approach 2:
The method uses specific voltage parameters (first voltage, second voltage, third voltage) to control the threshold voltages of selection transistors. By changing these voltage parameters during programming, the threshold voltages are precisely controlled to ensure reliable operation of vertically stacked transistors in the high-density array.
3Reliability
If Fowler-Nordheim tunneling and hot carrier injection mechanisms are used for programming, then the programming capability is improved, but the voltage complexity increases
Solution Approach 1:
The programming process uses periodic voltage application sequences. Voltages are applied in specific sequences and time intervals to bit lines and selection lines to enable Fowler-Nordheim tunneling and hot carrier injection mechanisms, ensuring reliable programming while managing voltage complexity through structured periodic action.
Solution Approach 2:
The method includes verification steps where threshold voltages of selection transistors are verified after programming. This feedback mechanism ensures that the programming using Fowler-Nordheim tunneling and hot carrier injection was successful, allowing corrective action if threshold voltages are not within desired ranges.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method ensures stable and reliable programming, reading, and erasing of memory cells by precisely controlling the threshold voltages of selection transistors, enhancing the overall performance and reliability of nonvolatile memory devices.
Implementation Method 1
at least one of the first selection transistors causes Fowler-Nordheim tunneling according to the first program voltage and the first voltage
Implementation Method 2
at least one of the second selection transistors causes Fowler-Nordheim tunneling according to the second program voltage and the fourth voltage
Data Source
AI summary
Disclosed is an operating method of a nonvolatile memory device, which includes programming the first selection transistors of the plurality of cell strings and programming the plurality of memory cells of the plurality of cell strings. The programming the first selection transistors comprises supplying a first voltage to a first bit line connected with a first selection transistor to be programmed and a different second voltage to a second bit line connected to a first selection transistor to be program inhibited; turning on the second selection transistors of the plurality of cell strings, and supplying a first program voltage to a selected first selection line among a plurality of first selection lines connected with the first selection transistors and a third voltage to an unselected first selection line among the plurality of first selection lines.