https://onlinelibrary.wiley.com/doi/pdf/10.1002/aelm.202100082

A Fully Integrated Ferroelectric Thin-Film-Transistor – Influence of Device Scaling on Threshold Voltage Compensation in Displays

Influence of Annealing Temperature on the Structural and Electrical Properties of Si-Doped Ferroelectric Hafnium Oxide

Ferroelectricity in crystalline hafnium oxide thin films is strongly investigated for the application in non-volatile memories, sensors and other applications. Especially for back-end-of-line (BEoL) integration the decrease of crystallization temperature is of major importance. However, an alternative method for inducing ferroelectricity in amorphous or semi-crystalline hafnium zirconium oxide films is presented here, using the newly discovered effect of electric field-induced crystallization in hafnium oxide films. When applying this method, an outstanding remanent polarization value of 2P
 $$_{\mathrm{R}}$$
  = 47 
 $$\upmu$$
 C/cm
 $$^{2}$$
 is achieved for a 5 nm thin film. Besides the influence of Zr content on the film crystallinity, the reliability of films crystallized with this effect is explored, highlighting the controlled crystallization, excellent endurance and long-term retention.

Electric field-induced crystallization of ferroelectric hafnium zirconium oxide.

Nonvolatile memories especially the ferroelectric (FE)-based ones such as ferroelectric tunnel junctions (FTJs) and ferroelectric field-effect transistors (FeFETs) have recently attracted a lot of attention. FTJs have been intensively researched for the last decade and found to be very promising memory devices due to their significant nondestructive readout advantage as compared to conventional ferroelectric random access memory (FRAM). However, more research is needed on FTJ devices to obtain reliable endurance and retention behavior. In this article, we demonstrate the characteristics and performance of zirconium-doped hafnium oxide-based FTJ devices in terms of FE switching and reliability. This is investigated for FTJ stack structure tuning as well as for the FE switching process in FTJ devices. The FTJ memory switching characteristics, the effects of polarization switching on the write conditions, and the impact of pulse width and pulse amplitude on switching are investigated. The impact of FE layer thickness and interface layer type/thickness are reported to obtain a maximum FTJ <inline-formula> <tex-math notation="LaTeX">${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ </tex-math></inline-formula> ratio (memory window) and reliable performance. The maximum <inline-formula> <tex-math notation="LaTeX">${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ </tex-math></inline-formula> ratio changes depending on the FE layer (zirconium-doped HfO2 layer) thickness (12, 8, 6, and 4 nm), the interface layer type (SiO2, Al2O3), and thickness (1 and 2 nm), indicating the maximum value of <inline-formula> <tex-math notation="LaTeX">${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ </tex-math></inline-formula> ratio for a 1 nm SiO2 interface layer stack. Moreover, a stable endurance of 104 cycles is reported and extrapolated measurements suggest stable retention for more than ten years. Time-dependent breakdown analysis was performed to investigate the reliability of devices indicating a lifetime of ten years.

Optimizing Ferroelectric and Interface Layers in HZO-Based FTJs for Neuromorphic Applications

The properties of hybrid ferroelectric (FE) and antiFE (AFE) films integrated in a single capacitor stack is reported. The stack lamination (4 × 5 nm) or (2 × 10 nm) using an Alumina (Al2O3) interlayer, material type (Si‐doped HfO2 (HSO) and Zr doped HfO2 (HZO)), precursor condition (TEMA‐Hf and Hf/ZrCl4), or dopant concentration (Si and Zr) are investigated for laminate stack properties. Optimized FE properties (higher 2Pr and a lower fraction of the monoclinic phase) are observed at (2 × 10 nm) laminates compared to a single 20 nm film thickness. The hybrid laminate stack as FE‐FE, AFE‐FE, DE‐FE, or DE‐AFE using (2 × 10 nm) based laminates are explored in terms of the output FE hysteresis (2Pr, 2Ec) and structural properties by X‐ray diffraction. The hybrid AFE‐FE stack shows the potential of tailoring the output FE hysteresis 2Ec by varying the fraction of the AFE phase. The hybrid AFE‐FE stack is studied for the HSO and HZO materials at optimal FE content for the first laminate layer while varying the Si or Zr content to stabilize different degrees of an AFE phase in the second laminate layer. The superposition of the hybrid AFE‐FE hysteresis shows a systematic 2Ec control. A model is developed to describe the tailored output FE hysteresis via the tuning of a hybrid AFE‐FE stack. The role of stack lamination at hybrid‐stabilized phases inside a single stack is explored with the aim for a controlled and optimized FE hysteresis shape toward a low power (2Ec) operation.

Tuning Hyrbrid Ferroelectric and Antiferroelectric Stacks for Low Power FeFET and FeRAM Applications by Using Laminated HSO and HZO films

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pssr.202100086

On the Origin of Wake-Up and Antiferroelectric-Like Behavior in Ferroelectric Hafnium Oxide

This paper presents a 60 GHz phase shifter, based on a coplanar waveguide (CPW) transmission line, loaded with ferroelectric hafnium zirconium oxide (HZO) variable metal-insulator-metal (MIM) varactors, developed for the back-end-of-line (BEoL) on-chip integration. Using the measured data of capacitance-voltage (C-V) characteristics of HZO and implementing the method-of-moments simulation, it was shown, that by changing the bias voltage between 0.95 and -3 V, the device shows a phase shift of 111° and a minimum insertion loss of -5.84 dB at 60 GHz. The chip area of the device is 0.206 mm2, making it the smallest among non-CMOS phase shifters.

A mmWave Phase Shifter Based on Ferroelectric Hafnium Zirconium Oxide Varactors

We demonstrate the feasibility of thermal energy recovery in the back end of line (BEoL) employing CMOS-compatible ferroelectric hafnium oxide. Efficient pyroelectric energy harvesting with a sizable power density of 92 mWcm-3 under typical thermal conditions is achieved. Our energy harvesting approach exceeds the efficiency limit of commonly-used thermoelectric materials, without using a heat switch. The low-voltage operation, scalability, and abundance in CMOS manufacturing make HfO 2 -based ferroelectrics promising candidates for integrated energy harvesting and solid-state refrigeration applications.

Energy Harvesting in the Back-End of Line with CMOS Compatible Ferroelectric Hafnium Oxide

This paper presents a tunable 60 GHz band-pass filter, based on a coplanar waveguide (CPW) transmission line, periodically loaded with ferroelectric Hafnium Zirconium Oxide (HZO) variable metal-ferroelectric-metal (MIM) capacitors (varactors), developed for back-end-of-line (BEoL) integration. Derived from the nonlinear capacitance of hafnium zirconium oxide and implementing the method-of-moments simulation, it was shown, that with changing the bias voltage between 0.95 and -3 V, the filter’s center frequency can be tuned between 60.5 and 69,7 GHz, respectively. Hereby, a minimum insertion loss of -3.3 dB is realized. The chip area of the filter is only 0.062 mm2, making it the smallest among tunable V-band filters.

Sukhrob Abdulazhanov

Papers

On the Origin of Wake-Up and Antiferroelectric-Like Behavior in Ferroelectric Hafnium Oxide

A mmWave Phase Shifter Based on Ferroelectric Hafnium Zirconium Oxide Varactors

Energy Harvesting in the Back-End of Line with CMOS Compatible Ferroelectric Hafnium Oxide

Electric field-induced crystallization of ferroelectric hafnium zirconium oxide.

A Tunable mmWave Band-Pass Filter Based on Ferroelectric Hafnium Zirconium Oxide Varactors