A Novel Structure to Improve the Erase Speed in 3D NAND Flash Memory to Which a Cell-On-Peri (COP) Structure and a Ferroelectric Memory Device Are Applied

Abstract

In this paper, a Silicon-Pillar (SP) structure, a new structure to improve the erase speed in the 3D NAND flash structure to which ferroelectric memory is applied, is proposed and verified. In the proposed structure, a hole is supplied to the channel through a pillar in the P+ crystal silicon sub-region located at the bottom of the 3D NAND flash structure to which the COP structure is applied. To verify this, we first confirmed that when the Gate Induced Drain Leakage (GIDL) erasing method used in the 3D NAND structure using the existing Charge Trap Flash (CTF) memory is applied as it is, the operation speed takes more than 10ms, for various reasons. Next, as a result of using the SP structure to solve this problem, even if the conventional erasing method was used until the thickness of the pillar was 20 nm, thanks to the rapidly supplied hole carriers, a fast-erasing rate of 1us was achieved. Additionally, this result is up to 10,000 times faster than the GIDL deletion method. Next, it was confirmed that when the pillar thickness is 10 nm, the erase operation time is greatly delayed by the conventional erasing method, but this can also be solved by appropriately adjusting the operating voltage and time. In conclusion, it was confirmed that, when the proposed SP structure is applied, it is possible to maximize the fast operation performance of the ferroelectric memory while securing the biggest advantage of the 3D NAND flash structure, the degree of integration.