ALD2019 Session AA3-TuA: ALD for Memory Applications I

Tuesday, July 23, 2019 4:00 PM in Grand Ballroom A-C

Tuesday Afternoon

Session Abstract Book
(313KB, May 5, 2020)
Time Period TuA Sessions | Abstract Timeline | Topic AA Sessions | Time Periods | Topics | ALD2019 Schedule

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4:00 PM AA3-TuA-11 Doped Hi-K ALD Films of HfOX and ZrOX for Advanced Ferroelectric and Anti-Ferroelectric Memory Device Applications:
Niloy Mukherjee, Jerry Mack, Somilkumar Rathi (Eugenus, Inc.); Zheng Wang, Anthony Gaskell, Nujhat Tasneem, Asif Khan (Georgia Institute of Technology); Milan Dopita, Dominik Kriegner (Charles University)

The discovery of ferroelectricity in doped hafnium oxide has generated excitement in the solid-state device community in recent years since hafnium oxide is a relatively simple oxide compared to traditional perovskite-based ferro-/anti-ferroelectric materials, and hafnium oxide is already used widely in the semiconductor industry. The discovery has inspired many researchers to study the system in further detail in the past few years. Recently, this group has discovered the ability to obtain anti-ferroelectric ZrOx in as-deposited ALD films alone, without the need for capping metallic electrodes or any post-deposition/post-metallization annealing. Tunability of the anti-ferroelectric behavior of ZrOx is also demonstrated using lanthanum doping and is co-related to changes in unit cell tetragonality with lanthanum doping. Process methods, including precursor delivery schemes and ALD deposition schemes, used to deposit doped HfOx and ZrOx-based ferroelectric and anti-ferroelectric films will be described in detail. Structural and electrical properties of such films will be described in detail and co-related.

[See figure in attachnent]

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4:30 PM AA3-TuA-13 ALD of La-Doped HfO2 Films for Ferroelectric Applications
Tatiana Ivanova, Perttu Sippola, Michael Givens (ASM, Finland); Hessel Sprey (ASM, Belgium); Teresa Maria Büttner, Patrick Polakowski, Konrad Seidel (Fraunhofer IPMS-CNT, Germany)

Ferroelectric (FE) HfO2 and its doped compounds [1] have received increasing interest for potential to harness these materials for non-volatile memory applications. ALD HfO2-based ferroelectrics can provide smooth process integration to silicon based semiconductor technology in contrast to e.g., perovskite FE materials. Especially, La-doped HfO2 films have been shown to exhibit superior ferroelectric responses with the so far highest reported remanent polarization for doped FE-HfO2 [2]. Nevertheless, a comprehensive in depth study of this promising material system has not been done.

This research covers highlights of the growth and FE properties of La-doped HfO2 ALD films. The 10 nm La-doped HfO2 films were deposited on 300 mm Si wafers in an ASM Pulsar® 3000 ALD reactor over a temperature range of 200-300 ° C. The La-doped HfO2 ALD process utilized HfCl4 and a novel lanthanum precursor with co-reactant oxidants. Spectroscopic ellipsometer and x-ray photoemission spectroscopy were used to study the film growth and composition properties, respectively. In addition, La-doped HfO2 crystallization kinetics were studied with in-situ x-ray diffractometry (IS-XRD). The FE properties were studied via fabrication and electrical characterization of planar metal-ferroelectric-metal capacitors (MFMCap).

Control of La-doped HfO2 in the range of [La] ~ 1-10 % (based on 100*[La]/( [La] + [Hf])) was studied by varying the ratio of LaOx:HfO2 subcycles during the ALD process. The La-doped HfO2 growth rate and residual C and Cl impurity concentrations were studied as a function of LaOx:HfO2 subcycle ratio and temperature for as-deposited films. IS-XRD analysis during high temperature annealing revealed the presence of the desired high symmetry phase of FE hafnium oxide for low [La] (1-5 %) and lower temperature (200-250 ° C) deposited samples, while samples with higher [La] showed an even stronger stabilization of the film which showed electrically no FE behavior. Crystallization temperatures increased with increasing La content, while it decreased with increasing deposition temperature: e.g. [La]~2 % samples deposited at 200-300 ° C crystallized at 615-470 ° C, respectively. The MFMCap studies confirmed the presence of strong FE responses for the low La content films exhibiting maximum remanent polarization of 26.5 µC/cm2 (post cycle conditioning) for [La]~2 % films deposited at 250 ° C.

[1] T. S. Böscke, et al., Applied Physics Letters 99, 102903 (2011)

[2] J. Müller et al., IEEE International Electron Devices Meeting (2013)

4:45 PM AA3-TuA-14 Characterization of Multi-Domain Ferroelectric ZrO2 Thin Films for Negative Capacitance and Inductive Responses
Yu-Tung Yin, Po-Hsien Cheng, Yu-Sen Jiang, Jay Shieh, Miin-Jang Chen (National Taiwan University, Republic of China)
By using a specific plasma-enhanced atomic layer deposition (PEALD) process, an as-deposited nanoscale ferroelectric ZrO2 (nano-f-ZrO2) thin film has been prepared. A unique periodically arranged crystalline has been observed under nano-beam electron diffraction (EBED ) and dark field TEM images, indicating the presence of multi-domain structure in nano-f-ZrO2. From the large-signal RLC oscillations in time domain analysis, the existence of positive imaginary part of the impedance, enhancement of small-signal capacitance of the series-connected capacitances, and the sub-60mV/dec subthreshold swing in nanoscale transistors, the multi-domain nano-f-ZrO2 has provided the experimental observation for the inductive behavior and negative capacitance induced by the net polarization switching. According to the theoretical calculation, the net polarization switching of multi-domain nano-f-ZrO2 produces an effective electromotive force which is similar in behavior with Lenz’s law, leading to the inductive responses and the negative capacitance effect. Since the as-deposited multi-domain nano-f-ZrO2 thin film provides a significant inductance behavior compared to conventional inductors, the PEALD deposited nano-f-ZrO2 would become a promising material in a variety of applications including nanoscale transistors, filters, oscillators, and radio-frequency integrated circuits. View Supplemental Document (pdf)
5:00 PM AA3-TuA-15 Scaling Ferroelectric Hf0.5Zr0.5O2 on Metal-Ferroelectric-Metal (MFM) and Metal-Ferroelectric-Insulator-Semiconductor (MFIS) Structures
Jaidah Mohan, Heber Hernandez-Arriaga, Harrison Sejoon Kim, Ava Khosravi, Akshay Sahota (The University of Texas at Dallas); Robert Wallace (University of Texas at Dallas); Jiyoung Kim (The University of Texas at Dallas)

Ferroelectricity in Hafnium Zirconate (HZO) has recently garnered interest due to the possibility of achieving sub-60mV/decade Subthreshold swing (SS) at room temperatures [1]. Such steep slope behavior could lead to various advantages like reducing static power dissipation and lowering operating voltages. “Negative Capacitance” is the currently proposed mechanism for such behavior but substantial claims and controversies are still being reported. Big mystery questions remain unsolved, (i) can hysteresis free switching continue to get steeper even at GHz frequencies? (ii) Can negative capacitance really be stabilized Nevertheless, various observations of sub-60 SS swing have been reported using a ferroelectric material as the gate dielectric [2][3]. In this work, we study scaling of HZO on Metal-Ferroelectric-Metal (MFM) and Metal-Ferroelectric-Insulator-Semiconductor (MFIS) structures which can further aid in reducing the operating voltages.

In this study, the ferroelectric properties of HZO was studied on MIM and MFIS structures, scaling down to 3nm. HZO was deposited using TDMA-hafnium (Hf[N(CH3)2]4), TDMA-zirconium (Zr[N(CH3)2]4), and O3 as the Hf-precursor, Zr-precursor and oxygen source respectively at 250°C. Blanket TiN (90 nm thick) electrodes were deposited after the HZO deposition as the stress given by the TiN electrode helps in crystallizing HZO into the ferroelectric phase. Then, rapid thermal annealing was done at 450oC in an N2 atmosphere for 60s to crystallize the HZO films. A conventional photolithography/etching process was used to make capacitors of different diameters. Grazing Incidence X-ray Diffraction (GIXRD) confirms that the ferroelectric orthorhombic phase is stable for HZO deposited on top of HF treated Silicon. The ferroelectric HZO film was scaled up to 5nm on top of Silicon and showed significant ferroelectric properties while 4nm and 3nm HZO showed very high leakage properties. Effects or reannealing to increase the grain size and hence the ferroelectric behavior was also studied. It was also observed that as the ferroelectric thickness decreases or the SiO2 thickness increases, there is an increase in the ferroelectric dipole relaxation, i.e. the ferroelectric domains are naturally tend to orient themselves in a particular direction.

REFERENCES:

[1] S. Salahuddin et al, Nano Lett., vol. 8, no. 2, pp. 405–410, 2008.

[2] S. Dasgupta, et al, IEEE J. Explor. Solid-State Comput. Devices Circuits, vol. 1, pp. 43–48, 2015.

[3] A.I. Khan et al., IEEE Electron Device Lett., vol. 37, no. 1, pp. 111–114, 2016.

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5:15 PM AA3-TuA-16 Interface Characteristics of MIM Capacitors using Vanadium Nitride Electrode and ALD-grown ZrO2 High-k Dielectric Film
Jae Hyoung Choi, Younsoo Kim, Hyung Ik Lee, Han-Jin Lim, Kihyun Hwang, Seok Woo Nam, Ho-Kyu Kang (Samsung Electronics, Republic of Korea)

One of the most critical challenges for DRAM (Dynamic Random Access Memory) downscaling is cell capacitor technology, and so far ZrO2 and TiN film have been adopted as a high-k dielectric and an electrode material respectively, for the capacitor application [1]. ZrO2 film has been spotlighted in TiN/Insulator/TiN (TIT) capacitor due to its high dielectric constant, wide band gap, and thermal stability [2].

A wide variety of DRAM capacitor electrodes are currently being evaluated as replacements for TiN including VN, HfN, and Ru. Ru-base electrode has advantage of high work function but also has cost and integration problem. Thermally robust HfN/HfO2 gate stack structure was reported with scaling down of equivalent oxide thickness (Toxeq.) less than 10Å and several attempts to prepare HfN films by metal organic chemical vapor deposition (MOCVD) have been continued [3,4]. Even though Vanadium Nitride (VN) exhibits high melting point, chemical inertness, low resistivity, and high work function from 5.05 to 5.15eV, very little is known about its qualities as DRAM capacitor electrode [5].

In this study, we fabricated new MIM (Metal/Insulator/Metal) capacitor using VN electrode and ALD-ZrO2 dielectric for DRAM capacitor. VN films (100~1,000Å) were deposited at different temperatures ranging from 25 to 500oC by reactive magnetron sputtering. ZrO2 films were used as a dielectric by atomic layer deposition (ALD) method with Tetra-Ethyl-Methyl-Amino-Zirconium (TEMAZ) liquid precursor and O3 reactant at the temperature of 250℃. ALD-ZrO2 films were progressed to post deposition anneal (PDA) in N2 atmosphere to crystallize the dielectric layer. Electrical properties of MIM capacitor with VN/ZrO2 combination such as capacitance, leakage current density and dielectric constant were compared with TiN/ZrO2 stack. Resistivity, composition, interfacial reaction, and crystalline structure of VN and ZrO2 films were analyzed by 4-point probe, Rutherford backscattering spectroscopy (RBS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Furthermore, the VN/ZrO2 interface effects on the electrical properties will be discussed in detail.

REFERENCES

1. S.K. Kim and C.S. Hwang, Electrochem. Solid-State Lett.11(3), G9 (2008).

2. C. W. Hill et al., J. Electrochem. Soc., 152(5), G386 (2005).

3. H.Y. Yu, et al., IEEE Electron Device Lett., 25, 70 (2004).

4. Y. Kim, et al., Proc. 15th EUROCVD, ECS 9, 762 (2005).

5. R. Fujii et al., Vacuum, 80(7), 832 (2006).

6. K. Yoshimoto et al., Jpn. J. Appl. Phys.45(1A) 215 (2006).

View Supplemental Document (pdf)
Session Abstract Book
(313KB, May 5, 2020)
Time Period TuA Sessions | Abstract Timeline | Topic AA Sessions | Time Periods | Topics | ALD2019 Schedule