Row Hammer Effect and Floating Body Effect of Monolithic 3D Stackable 1T1C DRAM

TL;DR

This study investigates the reliability of monolithic 3D stackable 1T1C DRAM, focusing on the row hammer and floating body effects, revealing mitigations and exacerbations of these phenomena through detailed modeling and parameter analysis.

Contribution

It provides a comprehensive analysis of the interplay between row hammer and floating body effects in 3D DRAM using TCAD modeling, highlighting mitigation strategies and device parameter impacts.

Findings

Row hammer effect is significantly mitigated in 3D DRAM compared to 2D.

Floating body effect is exacerbated by capacitive coupling in 3D stacking.

Device parameters like body thickness and doping influence the floating body effect.

Abstract

Monolithic 3D stackable 1T1C DRAM technology is on the rise, with initial prototypes reported by the industry. This work presents a comprehensive reliability study focusing on the intricate interplay between the row hammer effect and the floating body effect. First, using a TCAD model of a 3D DRAM mini-array, we categorize different cases of adjacent cells and show that the notorious row hammer effect induced by charge migration is significantly mitigated compared to 2D DRAM. However, we found that when incorporating an impact ionization model to account for the floating body characteristics of the silicon access transistor, the capacitive coupling between vertically stacked cells is severely exacerbated. Second, we conduct an in-depth investigation into the floating body effect itself. We systematically examine the dependence of this effect on key device parameters, including body thickness, doping concentration, and gate work function.