MRS Meetings and Events


DS02.09.06 2022 MRS Spring Meeting

Simulation-Guided Thermal Process Discovery for Flash Lamp Annealing Crystallization of On-Chip HfO2-ZrO2 Ferroelectric Memories

When and Where

May 12, 2022
3:45pm - 4:00pm

Hawai'i Convention Center, Level 3, 313C



Manohar Karigerasi1,Balreen Saini2,Zhouchangwan Yu2,Doug Campen1,Apurva Mehta1,Paul McIntyre2,1,John Baniecki1

SLAC National Accelerator Laboratory1,Stanford University2


Manohar Karigerasi1,Balreen Saini2,Zhouchangwan Yu2,Doug Campen1,Apurva Mehta1,Paul McIntyre2,1,John Baniecki1

SLAC National Accelerator Laboratory1,Stanford University2
The discovery of ferroelectricity in HfO<sub>2</sub>-ZrO<sub>2</sub> (HZO) alloys represents an important opportunity for fabrication of emerging non-volatile ferroelectric memory devices. Unlike conventional perovskite-based ferroelectrics, fluorite structure oxides such as HZO are already widely used in the semiconductor industry as gate insulators and dielectric materials and they can be scaled down to a few nanometers in thickness and still retain excellent polarization switching characteristics. The room temperature stable phase of bulk HZO is monoclinic and at higher temperatures, it transforms into tetragonal and cubic phases. There are four proposed orthorhombic HfO<sub>2</sub> phases adopting the space groups Pmn2<sub>1</sub>, Pca2<sub>1</sub>, Pbca, and Pbcm with two phases (Pmn2<sub>1</sub>, Pca2<sub>1</sub>) being ferroelectric. Most studies associate ferroelectricity with the Pca2<sub>1</sub> phase. Along with electrode capping effects, studies have shown that rapid heating and cooling a thin layer of HZO is critical to stabilizing the ferroelectric phase.<br/>Flash annealing is a technique that can be used to rapidly heat materials for durations on the order of tens of microseconds to a few milliseconds. The discharge from a capacitor bank can produce an instantaneous plasma in Xenon flash lamps and the light produced from the flash lamps are in turn, absorbed by the material stack. Unlike rapid thermal annealing, the flash annealing technique is orders of magnitude faster and the temperature depth profile will depend on the optical and thermal transport properties of the layers in the stack. With the right choice of layers and substrate, the steep temperature rise can be localized to the top few layers of the stack. This is useful in maintaining a low thermal budget to protect underlying interconnect structures during the fabrication of device layers integrated in the back-end-of-line (BEOL) on-chip.<br/>In this study, we fabricated MFM capacitor structures with a 10 nm HZO layer grown using plasma enhanced atomic layer deposition technique that is sandwiched between 10 nm sputtered TiN electrode layers. Using a custom modified flash lamp annealer, we apply short and rapid pulses to crystallize the ferroelectric phase. The instantaneous temperature rise during flash annealing for different substrates is simulated using COMSOL and we account for the temperature, wavelength, thickness and process dependent optical and thermal properties of the layers. The heat, that is generated through volumetric optical energy absorption, undergoes losses through conduction, convection and surface radiation. Prior studies have examined capacitors on Si, but capacitors integrated into the BEOL would be integrated on top of low k dielectrics. Thus, this study examines how thermally insulating layers below the TiN/HZO/TIN stack affect the temperature rise and crystallization of the HZO. We also found that the thickness of the top or bottom metallic layer was a major factor that contributed to the temperature rise observed in the HZO phase. The crystallization and formation of different phases was verified using grazing incidence x-ray diffraction measurements and ferroelectric characterization.


atomic layer deposition | x-ray diffraction (XRD)

Symposium Organizers

Veruska Malavé, National Institute of Standards and Technology
Vitor Coluci, UNICAMP
Kun Fu, University of Delaware
Hui Ying Yang, SUTD

Symposium Support

National Institute of Standards and Technology (NIST)

Publishing Alliance

MRS publishes with Springer Nature