Thermal Characterization of Ferroelectric Al_1-BN for Nonvolatile Memory

Area of Science:

• Materials Science
• Solid State Physics
• Electrical Engineering

Background:

• Boron (B)-substituted wurtzite aluminum nitride (Al_1-BN) is a novel ferroelectric material with potential for advanced memory applications.
• Compared to traditional ferroelectrics like Hf_1-ZrO₂ and PbZr_1-TiO₃, Al_1-BN offers lower growth temperatures and stable polarization.
• Wurtzite ferroelectrics may exhibit increased self-heating due to higher coercive fields and remanent polarization, posing challenges for device reliability.

Purpose of the Study:

• To investigate the self-heating effects in ferroelectric nonvolatile random-access memory (FeRAM) devices based on Al_1-BN.
• To understand the impact of boron composition on the thermal conductivity of Al_1-BN thin films.
• To analyze the transient thermal response and temperature rise in Al_1-BN based FeRAM under operational conditions.

Main Methods:

• Experimental measurement of thermal conductivity in Al_1-BN thin films with varying boron compositions (x).
• Micro-Raman thermometry to investigate the transient thermal response of an Al_0.93B_0.07N metal-ferroelectric-metal (MFM) capacitor.
• Device thermal modeling and simulation to validate experimental findings and predict performance under GHz frequency switching.

Main Results:

• Thermal conductivity of Al_1-BN thin films decreases significantly with increasing boron content, dropping from 40.9 W m^-1 K^-1 to 4.35 W m^-1 K^-1 as B composition (x) increases from 0 to 0.18.
• Experimental and simulation results indicate a potential temperature rise exceeding 150 °C in a 5 nm Al_1-BN FeRAM device operating at GHz frequencies.
• Thermal crosstalk in FeRAM arrays further exacerbates self-heating, leading to a predicted steady-state temperature rise an order of magnitude higher than in single cells.

Conclusions:

• The substantial reduction in thermal conductivity of Al_1-BN with increasing boron content is a critical factor for self-heating in FeRAM.
• High operating frequencies and thermal crosstalk in Al_1-BN based FeRAM can lead to significant temperature increases, potentially impacting device reliability and performance.
• Further research is needed to mitigate self-heating effects for the practical implementation of Al_1-BN in high-density, high-speed FeRAM.