Concept and Objectives

Main concept: “Normally-OFF” energy efficient Microcontroller Units for IoT

The microcontroller unit (MCU) with embedded non-volatile memory (eNVM) is at the heart of IoT devices, hierarchically placed between the sensor nodes and the host microprocessor with the task of pre-computing the data to reduce heavy loading of the host processor. In IoT applications, most of the power is consumed during the time the MCU is inactive so eNVM can be used to realize a “normally off” MCU drastically cutting power consumption. The idea is that the contents of the CPU are stored in the eNVM and subsequently CPU power is shut down to zero power consumption sleep mode before the data are restored during MCU wake-up period (see figure1).


Figure 1: Normally OFF MCU: (a) with e-Flash and (b) with low power, fast eNVM.

A robust eNVM with higher speeds, lower power and high endurance could be good replacement of eFlash in normally-off MCUs to reduce the energy spent during storage and retrieval of CPU content and to allow flexible Logic-in-Memory (LiM) designs which will further improve energy efficiency.

Ferroelectric HfO2: A key enabling material for a competitive and versatile eFeRAM

A number of NVM candidates with high speed/low power characteristics have emerged (STTRAM, ReRAM, FeRAM) and several working prototypes have been demonstrated but there is no clear winner at present. Among them, FeRAM has the highest endurance among all NVM candidates, low energy per bit and power consumption which could make it a potentially good candidate to replace Flash in embedded applications. However, the current embedded FeRAM with perovskite ferroelectrics (PbZrTO3 (PZT) or SrBi2(Ta, Nb)2O9 (SBT)) has serious problems with regard to memory cell scaling, compatibility with Si processing, manufacturability and cost that inhibit development as a mainstream eNVM solution. New ferroelectric materials which overcome the shortcomings of present day FeRAM are needed.

We will use new ferroelectric HfO2-based materials to develop a competitive and versatile FeRAM technology for eNVM solutions. The high-k HfO2 gate dielectric is a key material for modern nanoelectronics since it is compatible with Si technology and has allowed the scaling of advanced CMOS. The recent discovery of ferroelectricity in HfO2 creates the prospect that this material may impact other areas such as embedded memory by allowing scaling of FeRAM cells to increase storage capacity.

Moreover, ferroelectric HfO2 could be integrated into transistor gates for 1T FeFET memory cells with non-destructive read, integrated in the FEOL with CMOS. This opens the possibility of realizing new, fine grained LiM designs to enable the merging of logic and memory and to significantly improve energy efficiency of processing and storage units.

Ferroelectric HfO2 integrated in the gate of transistor could also produce negative capacitance FETs (NCFETs) functioning as low power steep slope switches to further boost low power/high performance operation of LiM circuits.

Technical Objectives

3eFERRO faces significant technical challenges and must attain the following four technical objectives to advance beyond the state of the art:

  1. Optimization of Ferroelectric Materials & Interface
  2. Fine-grained LiM design & architecture
  3. Integration of Ferroelectric- Hf(Zr)O2-based NVM arrays with CMOS
  4. Memory test, validation & benchmarking

EU flag© {2018} 3εFERRO - Energy Efficient Embedded Non-volatile Memory & Logic based on Ferroelectric Hf(Zr)O2
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 780302. All Rights Reserved. - Powered by puBBuh