ALD/ALE 2021 Session EM11: Emerging Materials Poster Session

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(284KB, Jun 9, 2021)
Time Period OnDemand Sessions | Topic EM Sessions | Time Periods | Topics | ALD/ALE 2021 Schedule

EM11-1 Strategies for High-Quality Nitride and Oxide Stacks by Plasma ALD
Yi Shu, Felicia McGuire, Agnieszka Kurek, Owain Thomas, Harm Knoops (Oxford Instruments Plasma Technology)

Many applications in industry require the deposition of nitrides and oxides with high purity and with high-quality interfaces. The focus of most atomic layer deposition (ALD) studies is on the deposition of a single layer in a dedicated deposition chamber. This contribution highlights a set of strategies for high-quality nitride and oxide stacks deposited by ALD in a single run in a single chamber. As an example, an HfO2/SiNx multilayer is demonstrated with <5% oxygen in the nitride.

Low oxygen content is a challenge for nitride deposition, especially when lines and chambers might contain oxygen and water traces from a previous deposition. To demonstrate a high-quality oxide and nitride stack, HfO2 using TDMAHf and O2 plasma and SiNx using BTBAS and N2 plasma are employed. The depositions are carried out in a FlexAL system in a single run and to get the best SiNx the residence time was minimized by a combination of turbo pumping, chamber heating and pressure and flow control.1 For other ALD nitride processes substrate biasing could be employed to lower oxygen content, but in the case of SiNx this is less effective.2 When switching from oxide to nitride deposition, the following strategies are employed:

  • Strong purging and pumping of any gas lines that could contain oxygen or oxygen byproducts.
  • TDMAHf precursor pulses to scavenge possible oxygen by-products.
  • Plasma treatment of the chamber and wafer surface.

After the subsequent deposition of the nitride the surface is exposed to a plasma post-treatment to further densify the material and protect it against oxidation. Using this strategy an alternating stack of HfO2 and SiNx was deposited with individual layer thicknesses of 20 nm. XPS depth analysis indicated that even with this relatively fast switching, oxygen content levels <5% were obtained for SiNx (XPS analysis by Dr. Shihong Xu, nanoFAB Centre, University of Alberta). This example and general strategies for such oxide and nitride stacks will be presented.

  1. Knoops et al.,Appl. Phys. Lett.107, 014102 (2015)
  2. Faraz et al., Plasma Sources Sci. Technol.28, 024002 (2019)
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EM11-2 Compositionally Graded Laminate ALD Films
Alexandru Pavel, Vasil Vorsa (Greene Tweed, Inc.)

To prevent contamination of microelectronic devices during semiconductor processing, chamber components of semiconductor tools are often coated with high purity ceramic coatings such as alumina or yttria that exhibit high resistance to plasma erosion in halogen environments.However, even these materials exhibit erosion over time leading to lower yield and costly down time, especially as the industry moves to smaller node sizes.

To overcome these limitations, there has recently been a major effort to find new coating materials and processes leading to improved plasma erosion resistance. There are now emerging plasma-resistant coatings deposited by atomic layer deposition (ALD). Advantages of ALD include conformal, dense, and pinhole-free film that can coat complex 3D shapes and high-aspect ratio holes.

One weakness with many coatings, including ALD, is the transition from one material composition to another.For example, the transition from substrate to film or from one film composition to another.Typically, in ALD, the film-substrate interface transitions abruptly within an atomic spacing of 1-2 Å.This can lead to high stress gradients confined to a narrow planar region potentially leading to poor film adhesion, especially where smooth surfaces and large CTE mismatches are present.

To overcome this drawback, ALD films can be deposited in such a way (US20200131632A1) that the composition is smoothly transitioned from one material to another, thus avoiding narrowly confined stress gradients.In this work, we present plasma resistant multi-layer coatings that exhibit excellent bonding of films to substrates formed by gradually varying the chemical composition from substrate to film and from one film type to another in a technique called Compositionally Graded Laminates (CGL).Examples of Compositionally Graded Laminate films of Y2O3-Al2O3, Y2O3-SiO2, and Y2O3-ZrO2 systems will be presented.

In addition to the semiconductor industry, this technique may be used to prepare and/or to coat substrates that form components useful in a variety of industries, especially those where components may be exposed to high temperatures and/or corrosive chemicals. For example, Compositionally Graded Laminates may be used on components that are found in equipment or devices used in aerospace, energy storage, pharmaceutical production, food processing, oil field applications, military and/or maritime applications, industrial manufacturing, and scientific and/or diagnostic instrumentation.

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EM11-3 In Situ Electrical Conductance to Measure Vapor Phase Infiltration (VPI) Doping Kinetics of Semiconducting Polymers
Kristina Malinowski, Shawn Gregory, Oliver Hvidsten, Alexandra Jungreis, Mark Losego (Georgia Institute of Technology)
This poster will show our development of in situ electrical conductance measurements during vapor phase infiltration (VPI) of polyaniline (PAni) thin films with titanium tetrachloride (TiCl4) to achieve electrical doping. In situ measurements during vapor phase processes provide abundant information about reaction kinetics and mechanisms that could not be acquired with ex situ data alone. The field of vapor doping semiconducting polymers lacks a robust understanding of doping mechanisms and their respective kinetics. Therefore, the vapor doping community stands to benefit from the implementation of in situ measurements. Here, we demonstrate how in situ conductance correlates with ex situ characterization and propose a sequence of in situ doping mechanisms. Dosing and holding TiCl4 in a chamber where hydroxyl groups are present can lead to both oxidative and acid doping of PAni films. TheTiCl4 vapor can directly oxidatively dope PAni while the HCl byproduct of TiCl4+ -OH can lead to acid doping. During the first dose and hold of TiCl4, in situ conductance measurements show that varying the TiCl4 dose pressure changes the rate and total conductance. Then, purge, pump and isolate steps remove unentrapped TiCl4 from the chamber. Dosing and holding H2O allows further acid doping, oxidative dedoping and oxide formation. Acid doping is in competition with dedoping and oxide formation to increase and decrease conductance, respectively. The in situ conductance measurements show decreasing conductance rates with increasing initial TiCl4 pressures, suggesting that acid doping dominates at low pressures and dedoping and oxide formation dominates at high pressures. The ex situ characterization of the thin films validates these suggested mechanisms. Opposite pressure-conductance correlations between the TiCl4 dose and H2O dose present an opportunity for optimizing PAni conductivity, aided by a thorough understanding of in situ kinetics. PAni doping can be further controlled by managing the reactor wall chemistry. If the reactor is first exposed to a precursor reactive towards hydroxyls but does not create an acid byproduct (for example trimethyl aluminum, TMA), then the walls can be passivated. Consequently, when TiCl4 is dosed, it does not react with the passivated walls, and HCl is not formed, so only oxidative doping occurs. During the subsequent water dose, the potential for acid doping is reintroduced through HCl formation within the film. In situ measurements demonstrate that this effectively isolates the two doping mechanisms. Thus, in situ measurements show promise in aiding design of complex processes for vapor doping of conductive polymers. View Supplemental Document (pdf)
EM11-4 Atomic Layer Deposition of Yttrium Oxide using a Liquid Yttrium Precursor, Y-08
Moo-Sung Kim, Se-Won Lee (EMD Electronics); Ming Fang, Joby Aldo, Jacob Woodruff, Ravindra Kanjolia, Bhushan Zope, Sergei Ivanov (EMD Electronics, USA)

Yttrium Oxide (Y2O3) films deposited by ALD have been extensively studied as a promising high-k material for future device manufacturing such as in MOSFETs or memory applications due to its wide band gap (~5.5 eV), high permittivity (>10), and high thermal stability. Pure or doped Y2O3 containing films have also been used in other applications such as in solid oxide fuel cells, protective coatings, photonics, and quantum information processing.

Herein, we report the studies of atomic layer deposition (ALD) of Y2O3 thin films using a newly developed volatile, scalable, liquid yttrium precursor, Y-08, with ozone and/or water as co-reactants.

A comparison of oxygen sources shows that “ozone followed by water” leads to a higher growth per cycle {0.81 Å/cycle} compared to either ozone-alone {0.51 Å/cycle}, or water-alone {0.16 Å/cycle}. The ALD window starts at 310 °C on the system tested, and the growth/cycle is 1.09 Å/cycle when saturation is achieved with both the Y-08 and oxygen sources doses.The refractive index ranges from 1.90 to 1.95. XPS analysis confirms that the bulk of film consists of exclusively oxygen and yttrium; but there was some carbon contamination on the film surface.

An yttrium oxide film deposited on a via with 20:1 aspect ratio (1800-nm deep, and 90-nm wide) shows excellent conformality when characterized by SEM (Figure 1), with film thickness ranging between 22.5 and 26 nm outside the via (Figure 2a), and 23 and 26 nm at the via bottom (Figure 2b).

We demonstrate that the liquid nature and high volatility of our new yttrium precursor promotes easier precursor delivery and more controllable ALD processes for manufacturing good quality Y2O3 thin films for future semiconductor applications.

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EM11-7 Direct sALD of MOF: An Improvement in the Nucleation Behavior
Maissa Barr, Soheila Nadiri (Friedrich-Alexander-University Erlangen-Nürnberg (FAU)); Dong-Hui Chen, Peter G. Weidler (Karlsruhe Institute of Technology (KIT)); Sebastian Bochmann (Friedrich-Alexander-University Erlangen-Nürnberg (FAU)); Helmut Baumgart (department of Electrical and computer Engineering); julien Bachmann (Friedrich-Alexander-University Erlangen-Nürnberg (FAU)); Engelbert Redel (Karlsruhe Institute of Technology (KIT))

Metal organic frameworks (MOFs), can be described as crystalline three-dimensional porous solids, with a high surface area, which have attracted considerable attention in a wide range of applications e.g. in catalysis,hydrogen storage,gas-separations , thermoelectric applications or as chemical sensors.Up to the present time, low-temperature methods had to be used to grow MOFs thin films today by conventional solution-based techniques. However, traditional growing methods from solution like spin-coating, spray-coating or dip-coating generates MOFs thin films with a rather low film quality and an alarming lack of a precise film thickness control under 1 nm, which renders them unsuitable for most industrial applications and severely limits their future application potential.

Atomic layer deposition (ALD) provides this capability, but is limited by the necessity to use gaseous precursors in vacuum conditions at temperatures above 100°C. However hybrid organo-metalic compunds such as the MOFs are not accessible by ALD due sensitivity to temperature.

In this perspective, we have transferred the principles of ALD to precursors dissolved in liquid solvents. The ‘solution ALD’ (sALD) method can be implemented in a variety of microfluidic or slot-die processing devices. We have demonstrated that the principles of classical, gas-based ALD —self-limiting surface reactions— are reproduced in sALD. sALD shares the fundamental properties of standard ‘gas ALD’ (gALD), in particular the self-limiting surface chemistry and the ability to coat deep pores in a conformal manner Furthermore, sALD allows the experimentalist to design new, advantageous, reactions of known semiconductors (oxides, heavier chalcogenides), or to deposit materials otherwise inaccessible to ALD altogether, such as polymers, ionic solids, and metal-organic frameworks. They may be obtained in highly pure, crystalline form at room temperature, either as planar films or as conformal coatings of porous substrates. Based on these advances, we have been able to make the first sALD-derived MOFs.

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EM11-10 Thermal ALD Growth of Ir and IrOx Films Using (MeCp)Ir(COD) and Oxygen
Guo Liu, Jacob Woodruff, Toshiya Okamura , Dan Moser , Ravi Kanjolia, Bhushan Zope (EMD Electronics, USA)

Iridium is a noble metal with low oxygen permeability, high chemical stability and high work function. It is one of the most corrosion resistant metals and has a lower bulk resistivity (~5.0 µΩ-cm) than Ru (6.8 µΩ-cm). Due to these unique properties, iridium has been investigated for potential applications in semiconductor devices as gate electrodes, a seed layer or Cu diffusion barrier. On the other hand, IrO2 can be converted into Ir metal by H2 reduction, and IrO2 nanoparticles are some of the best catalysts with potential applications for oxygen evolution in electrolyzers, metal-air batteries, and photoelectrochemical water splitting.

Various Ir precursors have been reported for ALD and CVD growth of Ir and IrO2 films (1,2). O2 is the most common oxidizer. Among the known ALD Ir precursors, the cyclodienyl-based (RCp)Ir(COD) (R=Me, Et) have very high thermal stability, and the liquid (EtCp)Ir(COD) precursor has been studied extensively (3,4), while the low melting-point (~40°C) MeCp analogue, (MeCp)Ir(COD), has not received much attention although it is easier to synthesize and has a higher thermal stability than (EtCp)Ir(COD). We have studied the ALD growth behavior of Ir and IrO2 films using (MeCp)Ir(COD) and O2 on a number of oxide and metal nitride surfaces in a wide temperature range up to 425°C. High purity Ir films with low O and C have been obtained on oxide and nitride substrates with resistivity down to ~16 µΩ-cm under various deposition conditions as shown in Fig. 1. The growth behavior on oxide surfaces is more complex. IrOx formed under certain conditions with notably higher resistivities. For examples, IrOx formed at ~ 350°C with O2 on Al2O3 as shown in Fig. 1.


(1). V. Yu. Vasilyev, N. B. Morozova, T. V. Basova, I. K. Igumenova and A. Hassanet, RSC Adv., 5, 32034-32065 (2015)

(2) Jani Hämäläinen, Mikko Ritala, and Markku Leskelä, Chem. Mater.26, 786−801 (2014).

(3) Sung-Wook Kim, Se-Hun Kwon, Dong-Kee Kwak, and Sang-Won Kanga, J. Appl. Phys. 103, 023517 (2008).

(4). Yong Hwan Lim, Hana Yoo, Bum Ho Choi, Jong Ho Lee, Ho-Nyun Lee, and Hong Kee Lee, Phys. Status Solidi C 8, No. 3, 891–894 (2011).

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Session Abstract Book
(284KB, Jun 9, 2021)
Time Period OnDemand Sessions | Topic EM Sessions | Time Periods | Topics | ALD/ALE 2021 Schedule