Semiconductor Memory Pillar Block Insulating Film Thickness Variation
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Solution Overview
Problem
In semiconductor memory devices, reducing the cell size to increase memory density can lead to electrical field concentration and leak currents between word lines and semiconductor layers, deteriorating saturation characteristics due to the physical distance reduction.
Innovation Solution
The semiconductor memory device employs a memory pillar structure with a thick block insulating film in curved parts and a thinner film in flat parts, and in the second embodiment, a double-layer block insulating film configuration, to suppress leak currents by increasing the electrical field concentration path length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the cell size is reduced to increase memory density, then memory density is improved, but electrical field concentration occurs and leak currents increase between word lines and semiconductor layers
Solution Approach 1:
The block insulating film is configured with different thicknesses in different regions: a first thickness in a first region and a second thickness greater than the first thickness in a second region. This local variation in film thickness provides enhanced insulation where needed (in the second region with greater thickness) while maintaining overall memory density improvements from the reduced cell size
Solution Approach 2:
The invention introduces vertical dimensionality variation through the non-uniform block insulating film thickness. By creating a thickness gradient in the vertical direction (different thicknesses in different regions), the patent increases the electrical field concentration path length in specific areas without requiring overall cell enlargement, thus suppressing leak currents while maintaining high memory density
2Length of moving object
If the physical distance between word lines and semiconductor layers is reduced, then cell size is reduced and memory density increases, but leak currents increase due to electrical field concentration
Solution Approach 1:
The block insulating film thickness is locally optimized with a first thickness in a first region and a second thickness (greater than the first) in a second region. This local quality variation suppresses electrical field concentration and resulting leak currents in the second region while maintaining the reduced cell size for high memory density
Solution Approach 2:
The invention changes the physical parameter of the block insulating film thickness to suppress leak currents. By adjusting the film thickness parameter (creating regions with different thicknesses), the electrical field distribution is modified, increasing the field concentration path length and reducing harmful leak currents despite the reduced physical distance between word lines and semiconductor layers
Data Source
AI summary
A semiconductor memory device includes a first pillar. The first pillar includes a first portion and a second portion. The first portion includes a first semiconductor layer and a first insulating film on a side surface of the first semiconductor layer. The first pillar includes a first region that faces the first portion and a second region other than the first region. The second portion includes a first conductive film that is in contact with the first insulating film and a second insulating film. The second insulating film has a first thickness in a fourth direction within the second region and a second thickness in the second direction within the first region. The first thickness is greater than the second thickness.