Non-Volatile Memory Devices With Dummy Word Lines
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Solution Overview
Problem
There is a need for more highly integrated memory devices in the field of non-volatile memory, particularly in NAND-type configurations, to improve storage density and performance.
Innovation Solution
The design includes a semiconductor substrate with specific arrangements of word lines, ground select lines, and string select lines, featuring dummy word lines and varying spacings to reduce ground-induced leakage current and erase disturbances, along with a method of forming these structures using self-aligned double patterning techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ground select lines are placed close to memory cell strings to increase integration density, then device integration is improved, but ground-induced leakage current and erase disturbances increase
Solution Approach 1:
A dummy word line is introduced as an intermediary element between the ground select line and the memory cell word lines. This dummy word line acts as a buffer that intercepts and redirects the electric field, preventing direct coupling between the ground select line and memory cell strings, thereby reducing ground-induced leakage current while allowing the ground select line to remain close to the memory cell strings for high integration density
2Productivity
If ground select lines are placed close to memory cell strings to increase integration density, then device integration is improved, but erase disturbances increase
Solution Approach 1:
The dummy word line serves as a protective intermediary that shields memory cell word lines from erase disturbances generated by the ground select line. During erase operations, the dummy word line absorbs and dissipates the harmful electric field, preventing it from reaching and disturbing the memory cell strings, thus enabling close placement of ground select lines without compromising erase operation integrity
3Device complexity
If spacing between ground select lines and word lines is reduced to increase integration, then device integration is improved, but leakage current increases
Solution Approach 1:
The dummy word line is positioned between the ground select line and memory cell word lines to create an electric field barrier. This intermediary structure allows the physical spacing to be minimized for high integration while the dummy word line's presence prevents direct field coupling, thereby maintaining low leakage current despite reduced spacing
Solution Approach 2:
The dummy word line introduces a localized structural modification in the critical region between ground select lines and memory cell strings. By concentrating the protective function in this specific local area, the overall device can maintain high integration density while the localized dummy word line structure prevents leakage current without affecting other regions
Data Source
AI summary
A non-volatile memory device may include a semiconductor substrate including an active region at a surface thereof, a ground select line crossing the active region, and a string select line crossing the active region and spaced apart from the ground select line. A plurality of memory cell word lines may cross the active region between the ground select line and the string select line with about a same first spacing provided between adjacent ones of the plurality of word lines and between a last of the plurality of memory cell word lines and the string select line. A second spacing may be provided between the ground select line and a first of the plurality of memory cell word lines.