Interleaved String Driver Layout for Narrow-Pitch Memory Arrays
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Solution Overview
Problem
Current memory devices face challenges in minimizing pitch between string drivers, which limits the miniaturization of memory subsystems, as further reduction in pitch can adversely affect leakage current and breakdown voltage.
Innovation Solution
The use of deep trench isolation structures and interleaved string driver layouts with gated lightly doped drains (LDDs) reduces the effective distance between string driver contacts, allowing for a smaller pitch without compromising electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the pitch between string drivers is reduced to minimize memory device size, then the area of the memory device is reduced, but the leakage current increases and breakdown voltage decreases
Solution Approach 1:
The string driver structure is segmented into multiple components: deep trench isolation structures that divide the substrate into isolated regions, interleaved driver circuits that separate control functions, and gated LDD regions that segment the drain area. This segmentation allows each component to be optimized independently, enabling pitch reduction while maintaining electrical performance through the deep trench isolation barriers.
Solution Approach 2:
Different regions of the string driver are given different doping concentrations and structural properties. The deep trench isolation regions have high doping concentrations to prevent leakage, while the channel regions maintain appropriate doping for device operation. The gated LDD regions have graded doping profiles that provide local electrical optimization, allowing the pitch to be reduced without compromising overall device reliability.
2Area of stationary object
If deep trench isolation structures and interleaved layouts are used to reduce pitch, then the area is reduced, but the device complexity increases
Solution Approach 1:
Multiple functions are merged into unified structures: the deep trench isolation structures simultaneously provide electrical isolation and define the physical boundaries of the string driver regions. The interleaved layout merges the control signal routing with the driver transistor placement, eliminating separate routing layers. The gated LDD structures combine drain extension with gate control functions, reducing the need for separate isolation regions.
Data Source
AI summary
A memory device includes a first string driver circuit and a second string driver circuit that are disposed laterally adjacent to each other in a length direction of a memory subsystem. The first and the second string driver circuits are disposed in an interleaved layout configuration such that the first connections of the first string driver are offset from the second connections of the second string driver in a width direction. For a same effective distance between the corresponding opposing first and second connections, a first pitch length corresponding to the interleaved layout configuration of the first and second string drivers is less by a predetermined reduction amount than a second pitch length between the first and second string drivers when disposed in a non-interleaved layout configuration in which each of the first connections is in-line with the corresponding second connection.