Rigorous analysis on the operating mechanism of gate-injection ferroelectric flash

초록

In this paper, the operation mechanism of gate-injection ferroelectric flash (GI-FeFlash) is studied through technology computer-aided design (TCAD) simulations. It reveals that GI-FeFlash exhibits an extraordinarily large memory window (MW) compared to the sum of MWs of a ferroelectric field-effect transistor (FeFET) and a charge trap flash (CTF), attributed to the synergistic effects between the two mechanisms: a polarization switching and a charge trapping. These synergistic effects can be analyzed by two phenomena: 1) a trap-assisted polarization switching (TAPS) and 2) a polarization-assisted charge trapping (PACT). In the case of TAPS, the trapped charges in the charge trap layer (CTL) enhance the polarization in the ferroelectric (FE) layer by increasing the electric field of the blocking oxide (i.e., FE layer). On the other hand, in the case of PACT, the polarization in the FE layer helps the charge injection into the CTL by increasing the electric field of the tunnel oxide (TO). Furthermore, TAPS and PACT are also verified by the analytical models based on Gauss's law. Therefore, GI-FeFlash can achieve a large MW (similar to 14.9 V) with a low-program/erase voltage and a fast-speed operation through the complementary relations between the two mechanisms.