/Ferroelectric memories: multi-layers stacks with tailored physical and electric properties by atomic layer deposition

Ferroelectric memories: multi-layers stacks with tailored physical and electric properties by atomic layer deposition

PhD - Leuven | More than two weeks ago

Develop in depth understanding on the inter-dependence of physical and ferroelectric properties of multi-layer stacks deposited by atomic layer deposition with applications in ferroelectric memories.

​In the last 5 years, has been a surge of technological interest in ferroelectric hafnium zirconium oxides (HZO) thin films as ferroelectric materials for emerging memories. Ferroelectricity in fluorite type of ferroelectric oxides has been explained by appearance of polar orthorhombic Pca21 phase in HZO or HfO2 polymorphic oxides. Thickness downscaling, grain size, or doping, mainly with transitional metals, are known to favor stabilization of desired orthorhombic phase. However, the ferroelectric properties under applied electrical field (such as remanent polarization, coercive field and especially endurance) are strongly dependent on the adjacent layers present in the final device stacks (metals, semiconductor and dielectric oxides) and the thermal treatment process conditions. High endurance and wake-up free ferroelectric stacks with sustained remanent polarization can be achieved by careful tuning of dopant content, layers thickness and the choice of the metal electrodes and interfacial layers. The resultant strain in the ferroelectric layer exerts a definitory effect on the ferroelectric response.

In this PhD  you will explore and evaluate novel doped HZO based stacks with applications in ferroelectric memory such as 1T-1C FERAM and FEFET architectures. The goal is to evaluate the physical properties (e.g. crystalline phase, texture, strain, grain  morphology) in the designed multi-layer stack films and correlate  with ferroelectric properties (remanent polarization, endurance, leakage, capacitance, breakdown voltage) by developing further understanding in the relation between the material characteristics, process factors and evolution of ferroelectric response under an applied electrical field.  The complexity of the stacks involving different layers (ferroelectric, metal, dielectric and semiconductor materials) raises a tremendous challenge in stabilization of ferroelectric phases under external stimuli, in understanding the evolution of remanent polarization where several mechanisms have proposed to explain the wake-up behavior, maximum polarization, fatigue and retention. A cross-team collaboration between the material and device experts will fill the gap in understanding this relation and allow designing stacks with improved electrical response for ferroelectric based memories.

Required background: The candidate should have recently obtained a Master in Materials Science, Materials Engineering , Nanotechnology, Physics, Chemical Engineering or Electrical Engineering. 

Type of work: 10% literature study, 90% experimental work (depending on the interest of the student a combined experimental/theoretical investigation might be possible)

Supervisor: Jan Van Houdt

Daily advisor: Mihaela Ioana Popovici

The reference code for this position is 2022-132. Mention this reference code on your application form.