Vertical NAND Flash Memory Contact Plug Spacing Optimization
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Solution Overview
Problem
The existing vertical NAND flash memory devices face challenges in maintaining a sufficient space margin between contact plugs and dummy pillars, which can lead to defects during the formation of contact holes, particularly affecting the reliability and efficiency of the device.
Innovation Solution
The proposed solution involves a vertical NAND flash memory device design where the distance between the first contact plug and adjacent second contact plugs is greater than the distances between adjacent second contact plugs, and the distance between the first contact plug and adjacent dummy pillars is also optimized, allowing for improved space margins and easier etching processes. This is achieved by varying the distances between contact plugs and dummy pillars, and shaping the contact plugs to increase their area, such as forming them in elliptical or peanut shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If dummy holes are formed at boundaries between word lines to prevent collapse during replacement process, then structural stability is improved, but space margin between contact plug and dummy pillar is reduced
Solution Approach 1:
The patent applies local quality by differentiating the treatment of contact plugs based on their position. First contact plugs (at boundaries between pads) are given larger widths than second contact plugs (within pads). This localized differentiation allows the boundary contact plugs to have sufficient space margin while maintaining the structural stability provided by dummy pillars, thus resolving the contradiction between stability and space margin.
Solution Approach 2:
The patent implements asymmetry by creating non-uniform contact plug widths across different locations. The first contact plugs have a first width while second contact plugs have a second width that is smaller than the first width. This asymmetric design optimizes the space margin for boundary contact plugs without unnecessarily reducing the area of internal contact plugs, thereby maintaining both structural stability and adequate space margins.
2Ease of manufacture
If uniform distance is maintained between all adjacent contact plugs, then manufacturing simplicity is improved, but space margin at boundaries is insufficient leading to defects
Solution Approach 1:
The patent applies local quality by differentiating the treatment of contact plugs based on their position. First contact plugs (at boundaries between pads) are given larger widths than second contact plugs (within pads). This localized differentiation allows the boundary contact plugs to have sufficient space margin while maintaining the structural stability provided by dummy pillars, thus resolving the contradiction between stability and space margin.
Solution Approach 2:
The patent implements asymmetry by creating non-uniform contact plug widths across different locations. The first contact plugs have a first width while second contact plugs have a second width that is smaller than the first width. This asymmetric design optimizes the space margin for boundary contact plugs without unnecessarily reducing the area of internal contact plugs, thereby maintaining both structural stability and adequate space margins.
Data Source
AI summary
Provided is a vertical NAND flash memory device. The vertical NAND flash memory device may include word lines formed on a substrate, a plurality of pads horizontally extending from the word lines, and contact plugs connected to respective pads. The contact plugs may include a first contact plug connected to a lowermost pad that is closest to the substrate, and a set of second contact plugs each second contact plug connected to a corresponding pad of the plurality of pads. A first distance between the first contact plug and a second contact plug of the set of second contact plugs that is adjacent to the first contact plug may be different from second distances between adjacent contact plugs of the set of second contact plugs. The second distances may be substantially the same as each other.