scholarly journals Origin of Enhanced Thermal Atomic Layer Etching of Amorphous HfO2

2021 ◽  
Author(s):  
Rita Mullins ◽  
Jose Julio Gutiérrez Moreno ◽  
Michael Nolan
Keyword(s):  
Metal Oxides ◽  
First Principles ◽  
Etch Rate ◽  
Atomic Layer ◽  
Atomic Level ◽  
Oxide Surface ◽  
Exchange Reactions ◽  
Adsorption Sites ◽  
High K ◽  
Atomic Layer Etching

HfO2 is a high-k material that is used in semiconductor devices. Atomic-level control of material processing is required for the fabrication of thin films of high-k materials at nanoscale device sizes. Thermal atomic layer etching (ALE) of metal oxides, in which up to one monolayer of material can be removed, can be achieved by sequential self-limiting (SL) fluorination and ligand-exchange reactions at elevated temperatures. First-principles based atomic-level simulations using density functional theory (DFT) can give deep insights into the precursor chemistry and the reactions that drive the etch of metal oxides. A previous study examined the hydrogen fluoride (HF) pulse in the first step in the thermal ALE process of crystalline HfO2 and ZrO2. This study examines the HF pulse on amorphous HfO2 using first-principles simulations. The Natarajan-Elliott analysis, a thermodynamic methodology is used to compare reaction models representing the self-limiting and spontaneous etch processes taking place during an ALE pulse. For the HF pulse on amorphous HfO2, we found that thermodynamic barriers impeding spontaneous etching are present at ALE relevant temperatures. HF adsorption calculations on the amorphous oxide surface is studied to understand the mechanistic details of the HF pulse. A HF molecule adsorbs dissociatively by forming Hf-F and O-H bonds. HF coverages ranging from 1.1 ± 0.3 to 18.0 ± 0.3 HF/nm2 are investigated and a mixture of molecularly and dissociatively adsorbed HF molecules is present at higher coverages. A theoretical etch rate of -0.82 ± 0.02 Å/cycle for amorphous HfO2 was calculated using a maximum coverage of 9.0 ± 0.3 Hf-F/nm2. This theoretical etch rate is greater than the theoretical etch rate for crystalline HfO2 that we previously calculated at -0.61 ± 0.02 Å/cycle. Undercoordinated atoms and void regions in amorphous HfO2 allows for more binding sites during fluorination whereas crystalline HfO2 has a limited number of adsorption sites.

Mechanism of the HF Pulse in the Thermal Atomic Layer Etch of HfO2 and ZrO2: A First Principles Study

2019 ◽  
Author(s):  
Rita Mullins ◽  
Suresh Natarajan ◽  
Simon D. Elliott ◽  
Michael Nolan
Keyword(s):  
First Principles ◽  
Ligand Exchange ◽  
Elevated Temperatures ◽  
Atomic Layer ◽  
Level Control ◽  
Exchange Reactions ◽  
Nanoscale Device ◽  
High K ◽  
Reaction Models ◽  
High K Materials

<div>HfO2 and ZrO2 are two high-k materials that are important in the down-scaling of semiconductor devices. Atomic level control of material processing is required for fabrication of thin films of these materials at nanoscale device sizes. Thermal Atomic Layer Etch (ALE) of metal oxides, in which up to one monolayer of the material can be removed, can be achieved by sequential self-limiting fluorination and ligand-exchange reactions at elevated temperatures. However, to date a detailed atomistic understanding of the mechanism of thermal ALE of these technologically important oxides is lacking. In this paper, we investigate the hydrogen fluoride pulse in the first step in the thermal ALE process of HfO2 and ZrO2 using first principles simulations. We introduce Natarajan-Elliott analysis, a thermodynamic methodology, to compare reaction models representing the self-limiting (SL) and continuous spontaneous etch (SE) processes taking place during an ALE pulse. Applying this method to the first HF pulse on HfO2 and ZrO2 we found that thermodynamic barriers impeding continuous etch are present at ALE relevant temperatures. We performed explicit HF adsorption calculations on the oxide surfaces to understand the mechanistic details of the HF pulse. A HF molecule adsorbs dissociatively on both oxides by forming metal-F and O-H bonds. HF coverages ranging from 1.0 0.3 to 17.0 0.3 HF/nm2 are investigated and a mixture of molecularly and dissociatively adsorbed HF molecules is present at higher coverages. Theoretical etch rates of -0.61 0.02 Å /cycle for HfO2 and -0.57 0.02 Å /cycle ZrO2 were calculated using maximum coverages of 7.0 0.3 and 6.5 0.3 M-F bonds/nm2 respectively (M = Hf, Zr).</div>

Mechanism of the HF Pulse in the Thermal Atomic Layer Etch of HfO2 and ZrO2: A First Principles Study

2019 ◽  
Author(s):  
Rita Mullins ◽  
Suresh Natarajan ◽  
Simon D. Elliott ◽  
Michael Nolan
Keyword(s):  
First Principles ◽  
Ligand Exchange ◽  
Elevated Temperatures ◽  
Atomic Layer ◽  
Level Control ◽  
Exchange Reactions ◽  
Nanoscale Device ◽  
High K ◽  
Reaction Models ◽  
High K Materials

<div>HfO2 and ZrO2 are two high-k materials that are important in the down-scaling of semiconductor devices. Atomic level control of material processing is required for fabrication of thin films of these materials at nanoscale device sizes. Thermal Atomic Layer Etch (ALE) of metal oxides, in which up to one monolayer of the material can be removed, can be achieved by sequential self-limiting fluorination and ligand-exchange reactions at elevated temperatures. However, to date a detailed atomistic understanding of the mechanism of thermal ALE of these technologically important oxides is lacking. In this paper, we investigate the hydrogen fluoride pulse in the first step in the thermal ALE process of HfO2 and ZrO2 using first principles simulations. We introduce Natarajan-Elliott analysis, a thermodynamic methodology, to compare reaction models representing the self-limiting (SL) and continuous spontaneous etch (SE) processes taking place during an ALE pulse. Applying this method to the first HF pulse on HfO2 and ZrO2 we found that thermodynamic barriers impeding continuous etch are present at ALE relevant temperatures. We performed explicit HF adsorption calculations on the oxide surfaces to understand the mechanistic details of the HF pulse. A HF molecule adsorbs dissociatively on both oxides by forming metal-F and O-H bonds. HF coverages ranging from 1.0 0.3 to 17.0 0.3 HF/nm2 are investigated and a mixture of molecularly and dissociatively adsorbed HF molecules is present at higher coverages. Theoretical etch rates of -0.61 0.02 Å /cycle for HfO2 and -0.57 0.02 Å /cycle ZrO2 were calculated using maximum coverages of 7.0 0.3 and 6.5 0.3 M-F bonds/nm2 respectively (M = Hf, Zr).</div>

A first-principles study of the atomic layer deposition of ZnO on carboxyl functionalized carbon nanotubes: the role of water molecules

2021 ◽  
Vol 23 (5) ◽  
pp. 3467-3478
Author(s):  
J. I. Paez-Ornelas ◽  
H. N. Fernández-Escamilla ◽  
H. A. Borbón-Nuñez ◽  
H. Tiznado ◽  
Noboru Takeuchi ◽  
...  
Keyword(s):  
First Principles ◽  
Ligand Exchange ◽  
Functional Group ◽  
Atomic Layer ◽  
High Reactivity ◽  
Water Molecules ◽  
Exchange Reactions ◽  
Layer Deposition ◽  
The Right

Atomic description of ALD in systems that combine large surface area and high reactivity is key for selecting the right functional group to enhance the ligand-exchange reactions.

(Invited) Volatile Products during Thermal Atomic Layer Etching of Metal Oxides and Elemental Metals

2021 ◽  
Vol MA2021-01 (21) ◽  
pp. 844-844
Author(s):  
Ann Lii-Rosales ◽  
Virginia Johnson ◽  
Sandeep Sharma ◽  
Andrew S Cavanagh ◽  
Steven M George
Keyword(s):  
Metal Oxides ◽  
Atomic Layer ◽  
Volatile Products ◽  
Atomic Layer Etching

In-situ Infrared Absorption Monitoring of Atomic Layer Deposition of Metal Oxides on Functionalized Si and Ge Surfaces

2007 ◽  
Vol 996 ◽  
Author(s):  
Min Dai ◽  
Jinhee Kwon ◽  
Ming-Tsung Ho ◽  
Yu Wang ◽  
Sandrine Rivillon ◽  
...  
Keyword(s):  
Growth Rate ◽  
Ir Spectroscopy ◽  
Metal Oxides ◽  
Infrared Absorption ◽  
Interfacial Layer ◽  
Atomic Layer ◽  
Chemical Functionalization ◽  
Layer Deposition ◽  
High K

AbstractThe nature of the interface between Si and Ge substrates and high-k dielectrics often controls the performance of MOSFET devices. Precleaning and/or chemical functionalization of the surfaces can dramatically affect the formation of an interfacial layer. We have used in-situ IR spectroscopy to probe the relevant interfaces during ALD growth for a variety of surface treatments, including H- and Cl-termination, and nitridation. This paper focuses on understanding of the mechanisms for interfacial SiO2 (or GeOx) formation during HfO2 growth using tetrakis-ethylmethylamidohafnium (TEMAH) as the metal precursor and water or ozone as the oxygen precursor. We find that impurities arising from incomplete ligand elimination during growth (e.g. OH for H2O processing and CO- and NO-containing species for O3 processing) are incorporated into the HfO2 film during growth. Upon annealing, most of these species react, but can also migrate to the interface. Nitridation of Si and Ge surfaces will in general prevent SiO2 or GeOx formation but can also affect the growth rate.

First Principles Modeling Of High-K Dielectric Materials

2002 ◽  
Vol 745 ◽  
Author(s):  
Gyuchang Jun ◽  
Kyeongjae Cho
Keyword(s):  
Metal Oxide ◽  
Metal Oxides ◽  
First Principles ◽  
Density Functional ◽  
Oxide Thickness ◽  
Dielectric Materials ◽  
Interface Layer ◽  
Dielectric Constants ◽  
High K ◽  
Interface Layers

ABSTRACTFirst-principles calculations are performed for high-K gate dielectric materials using model bulk and interface systems. Detailed electronic structures and atomic configurations are investigated for transition metal (Hf and Zr) oxide, metal doped silicate bulk system and a model Si-silicate interface system. Pseudo polymorphs of metal oxides are investigated to elucidate the underlying driving mechanisms in microscopic configurations of metal oxides and silicates in amorphous structures. We studied energetics and electronic structure of metal oxide pseudo morph with varying oxygen coordination. Dielectric constants of metal oxide and silicate materials are also investigated using the density functional perturbation theory method implemented in the ABINIT code. Electronic and dielectric properties of silica interface layers between high-κ dielectric and Si substrate are investigated leading to a confirmation that 1 nm is the physical limit of gate oxide thickness. Furthermore silica interface layer is found to have small dielectric constant of 3.4∼3.9.

scholarly journals Investigation on Ge0.8Si0.2-Selective Atomic Layer Wet-Etching of Ge for Vertical Gate-All-Around Nanodevice

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1408
Author(s):  
Lu Xie ◽  
Huilong Zhu ◽  
Yongkui Zhang ◽  
Xuezheng Ai ◽  
Junjie Li ◽  
...  
Keyword(s):  
Crystal Orientation ◽  
Field Effect ◽  
Etch Rate ◽  
Field Effect Transistors ◽  
Atomic Layer ◽  
Wet Etching ◽  
Isotropic Etching ◽  
Etching Selectivity ◽  
Oxide Removal ◽  
Atomic Layer Etching

For the formation of nano-scale Ge channels in vertical Gate-all-around field-effect transistors (vGAAFETs), the selective isotropic etching of Ge selective to Ge0.8Si0.2 was considered. In this work, a dual-selective atomic layer etching (ALE), including Ge0.8Si0.2-selective etching of Ge and crystal-orientation selectivity of Ge oxidation, has been developed to control the etch rate and the size of the Ge nanowires. The ALE of Ge in p+-Ge0.8Si0.2/Ge stacks with 70% HNO3 as oxidizer and deionized (DI) water as oxide-removal was investigated in detail. The saturated relative etched amount per cycle (REPC) and selectivity at different HNO3 temperatures between Ge and p+-Ge0.8Si0.2 were obtained. In p+-Ge0.8Si0.2/Ge stacks with (110) sidewalls, the REPC of Ge was 3.1 nm and the saturated etching selectivity was 6.5 at HNO3 temperature of 20 °C. The etch rate and the selectivity were affected by HNO3 temperatures. As the HNO3 temperature decreased to 10 °C, the REPC of Ge was decreased to 2 nm and the selectivity remained at about 7.4. Finally, the application of ALE in the formation of Ge nanowires in vGAAFETs was demonstrated where the preliminary Id–Vds output characteristic curves of Ge vGAAFET were provided.

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