Inverted-T Word Line Geometry for Non-Volatile Memory Isolation
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Solution Overview
Problem
In high-density semiconductor memory devices, the close proximity of word lines can lead to dielectric breakdown due to strong electric fields, resulting in word line to word line shorts, especially as feature sizes decrease, making it challenging to maintain electrical isolation and prevent programming disturbances.
Innovation Solution
The implementation of word lines with an inverted T-shape geometry, where the top portion is thinner than the bottom portion, increases the separation between adjacent word lines, reducing the electric field and enhancing electrical isolation through air gaps or solid dielectric materials, thereby reducing the likelihood of shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If word lines are placed in close proximity to increase storage density, then storage capacity per area is improved, but electric field strength increases causing dielectric breakdown and word line shorts
Solution Approach 1:
The patent transitions from planar word line geometry to three-dimensional inverted-T geometry. The vertical stem of the inverted-T extends downward beneath adjacent word lines, creating separation in the vertical dimension while maintaining horizontal proximity for high density. This dimensional change allows close packing without compromising electrical isolation.
Solution Approach 2:
The inverted-T word line structure nests the vertical stem within the space between adjacent word lines, effectively utilizing the three-dimensional space. The stem portion is positioned beneath the horizontal bars of neighboring word lines, creating a nested configuration that increases separation distance without increasing footprint area.
2Area of moving object
If feature sizes are decreased to increase storage density, then area efficiency is improved, but electric field concentration increases leading to dielectric breakdown
Solution Approach 1:
By introducing vertical extension through the inverted-T geometry, the patent adds a third dimension to the word line structure. This allows the effective separation distance to increase in the vertical direction while maintaining small horizontal feature sizes, thereby reducing electric field concentration without sacrificing area efficiency.
Solution Approach 2:
The inverted-T geometry creates local variation in the electric field distribution. The vertical stem provides enhanced separation specifically in regions where electric field concentration is most problematic, while the horizontal bars maintain close proximity for high density. This localized structural modification addresses the harmful electric field effects without compromising overall device density.
Data Source
AI summary
A non-volatile memory system, comprising non-volatile storage device with word lines having an inverted T-shape over floating gates. The inverted T-shape shape has a wider bottom portion and a thinner top portion. The thinner top portion increases the separation between adjacent word lines relative to the separation between the wider bottom portions. An air gap may separate adjacent word lines. The thinner top portion of the word lines increases the path length between adjacent word lines. The likelihood of word line to word line short may be decreased by reducing the electric field between adjacent word lines.