Semiconductor Memory Device Even Odd Cell String Programming
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Solution Overview
Problem
The reliability of program operations in semiconductor memory devices is compromised due to differences in program velocity and threshold voltage distribution between even and odd cell strings, leading to interference and reduced integrity.
Innovation Solution
A method and semiconductor memory device design that involves connecting even and odd bit lines to respective cell strings and applying specific program voltages to equalize channel potentials, using a second program permission voltage for even cell strings and a first program voltage for odd cell strings, and adjusting voltages to ensure similar channel potentials during programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the interval between memory cells is reduced to increase device integrity, then device integrity is improved, but interference between adjoining memory cells increases
Solution Approach 1:
The patent divides cell strings into even and odd groups and programs them in alternating sequences. This segmentation approach prevents continuous interference on adjacent cell strings by alternating which group is programmed, thereby maintaining device integrity while reducing cumulative interference effects.
Solution Approach 2:
The patent performs preliminary programming on even cell strings before programming odd cell strings. By completing programming on one group first, the system establishes a baseline state and then alternates to the other group, preventing interference accumulation and maintaining reliable threshold voltage distribution.
2Speed
If program operation is performed on even cell strings first, then program velocity of even cell strings is improved, but threshold voltage distribution becomes wide due to interference
Solution Approach 1:
The patent segments the programming process into two distinct phases: first programming even cell strings to high threshold voltage, then programming odd cell strings to low threshold voltage. This segmentation prevents interference-induced threshold voltage spread by ensuring that when one group is programmed, the other group remains in a stable state.
Solution Approach 2:
The patent implements periodic alternating programming between even and odd cell string groups. After completing programming on even strings, it switches to odd strings, creating a periodic pattern that prevents continuous interference on adjacent cells and maintains narrow threshold voltage distribution.
3Speed
If program operation is performed on odd cell strings after even cell strings, then program velocity of odd cell strings is improved, but interference between adjoining cell strings increases
Solution Approach 1:
The patent segments programming into sequential phases where even cell strings are programmed first to a first threshold voltage level, then odd cell strings are programmed to a second threshold voltage level. This segmentation ensures that interference does not accumulate continuously on adjacent cell strings.
Solution Approach 2:
The patent performs preliminary programming on even cell strings before proceeding to odd cell strings. By establishing the even strings in a stable programmed state first, the system creates a reference configuration that minimizes interference during subsequent programming of odd strings.
Data Source
AI summary
A semiconductor memory device and a method of operating a semiconductor memory device includes connecting selected even bit lines to selected even cell strings, programming memory cells in the selected even cell strings by using a second program permission voltage higher than a first program permission voltage, connecting selected odd bit lines to selected odd cell strings when programming of the memory cells is finished, and programming memory cells in the selected odd cell strings by using the first program permission voltage.