Material Choices for Tunnel Dielectric Layer and Gate Blocking Layer for Ferroelectric NAND Applications
Lance Fernandes, Prasanna Venkatesan Ravindran, Taeyoung Song, Dipjyoti Das, Chinsung Park, Nashrah Afroze, Mengkun Tian, Hang Chen, Winston Chern, Kijoon Kim, Jongho Woo, Suhwan Lim, Kwangsoo Kim, Wanki Kim, Daewon Ha, Shimeng Yu, Suman Datta, Asif Islam Khan
Abstract
We present an experimental study to compare the impacts of different dielectric materials - Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and SiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> used as the tunnel dielectric layer (TDL) and the gate blocking layer (GBL) on the performance of ferroelectric gate stacks for NAND storage applications. We considered the maximum memory window (MW) and the incremental step program pulse (ISPP) slope as the key performance metrics. In a gate stack with TDL, Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> gives higher MW and ISPP performance than SiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>. However, in the GBL gate stack, SiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> has a higher MW and ISPP slope than Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>. With SiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> GBL, a maximum MW window of 8.3V was achieved, enabling quad-level cell (QLC) capability. We show that for a similar thickness, SiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> as GBL has the better MW performance, and Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> as TDL has a better ISPP performance. This study shows that TDL and GBL with appropriate dielectric material can be used as tuning knobs to achieve the desired ISPP and MW performance for ferroelectric NAND applications.