A 4-Bit Double SONOS Memory (DSM) with 4 Storage Nodes per Cell for Ultimate Multi-Bit Operation

Abstract

We proposed a 4-bit double SONOS memory with two ONO layers, 4 storage nodes, for ultimate multi-bit operation and firstly demonstrate 4-bit operation using the physically separated 4 storage nodes. By using CHEI/HHI program/erase, each node was easily programmed and erased without any detrimental interference among the nodes. In the gate length of 120nm, the read/write margins of ~0.8V for front side (FS) and ~1.1V for back side (BS) at V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> =1.2V was obtained. The V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH </sub> shifts of ~1.5V for both program/erase (P/E) were observed with the P/E conditions, V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</sub> /V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FG</sub> =3/5V, 3/-4V for FS and VD/VBG=3.2/7V, 3.2/-5V for BS, respectively, with the duration of 1 ms. The V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub> windows of ~0.9V for FS and ~1.1V for BS were achieved even after 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> P/E cycles