Nonvolatile memory devices fabricated at a complementary metal–oxide–semiconductor (CMOS)-compatible temperature

High-performance nonvolatile memory devices integrated with ferroelectric Aluminum Scandium Nitride (AlScN) films that can be directly deposited on the silicon at low temperature (≤ 350 °C)

Problem:
Strong demand for high-density non-volatile memory (NVM) devices with low power consumption is being driven by new applications of non-von Neumann computing architectures, the Internet of Things (IoT), and artificial intelligence. Ferroelectric field effect transistor (FeFET)-based nonvolatile memories are the most compelling emerging NVM devices due to their high access speed, high endurance, and low energy consumption. However, applications of FeFETs suffer from the lack of reliable industrial-scale production of ferroelectric films and incompatibility with complementary metal–oxide–semiconductor (CMOS) processing temperatures.

Solution:
The researchers developed AlScN FeFET memory devices that integrate Aluminum Scandium Nitride (AlScN) films. The integration and fabrication process can be done at a CMOS-compatible temperature (≤350 °C). The resulting memory devices offer high performance with a large memory window ranging from 20 to 40 V, a high on/off ratio of over 106, and a maximum on-current of 3 mA with channel dimensions W/L = 12 μm/3 μm.

Technology Overview:
AlScN alloys have large coercive fields and high remnant polarizations, which allows them to be scaled into thinner ferroelectric layers with smaller FeFET gate dimensions while maintaining large memory windows and large bit density. The low deposition temperature (≤ 350 °C) of AlScN also allows for FeFET integration directly into a CMOS. The AlScN thin films are used as ferroelectric gate dielectrics in FeFET-based memories, so that film deposition can be done at a CMOS-compatible temperature.

Advantages:

Deposition of AlScN films can be done at a CMOS-compatible temperature (≤ 350 °C)
The on/off ratio of the fabricated AlScN FeFETs is ~106, 100+ times higher than currently available FeFETs.
The normalized memory window over the thickness of the ferroelectric film is 40 V/100 nm, which is the highest among all the reported FeFETs at room temperature.
The anticipated memory window on a 13-nm AlScN is 2X that of the HfZrO with the same thickness, which lowers the voltage required to polarize the gate dielectrics

Stage of Development:
Bench Prototype

Schematic of the experimental AlScN FeFET in On- and Off-States; the blue part represents the AlScN film.

Intellectual Property:
US Patent Pending

Reference Media:
Liu, X et al.; Nano Lett 2021 May 12 21(9): 3753

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