Unveiling the Future of Material Science: Key Takeaways from the MLD and ALD Webinar

In the dynamic world of material science, the recent Applied Materials Picosun webinar held on January 16, 2024 centered on Atomic Layer Deposition (ALD) and Molecular Layer Deposition (MLD), offered a deep dive into these groundbreaking technologies and their applications in crafting advanced functional properties. 

LINK to recording: Atomic layer deposition (ALD) and molecular layer deposition (MLD) together present an elegant technique for the deposition of novel inorganic-organic materials. (picosun.com)

The webinar was given by Topias Jussila, Doctoral Researcher, Aalto University, Finland. Let's explore how ALD and MLD are shaping the future of materials at the nanoscale.

The Emergence of MLD

Molecular Layer Deposition, though a relative newcomer compared to ALD, has quickly garnered attention for its unique capabilities. MLD, which operates on the principle of sequential molecular layering, offers a versatile platform for creating hybrid materials with tailored properties. The webinar expertly delineated the different types of MLD, such as metal-aliphatics, metal-aromatics, and inorganic-organic multilayers, each presenting its distinct advantages in material fabrication.

 

Synergy of ALD and MLD

The fusion of ALD with MLD emerged as a focal point of discussion. This combination enhances the material properties, allowing for precise control at the nanoscale. The synergy of ALD and MLD opens doors to innovative applications, particularly in microelectronics and nanotechnology, by creating materials with unprecedented electrical, optical, and mechanical properties.

 

Applications That Reshape Industries

The practical applications of MLD and ALD-MLD are vast and varied. Key areas include:

Flexible Barrier Layers: MLD is particularly effective in creating ultra-thin, flexible barrier layers that are impermeable to gases and moisture. This is crucial for applications like organic light-emitting diode (OLED) displays and flexible electronics, where moisture and oxygen can degrade the performance of the devices.

Encapsulation: MLD provides an excellent method for encapsulating sensitive components, protecting them from environmental factors without compromising their functionality.

Photocatalysis: MLD materials are used in photocatalysis applications, which are important in environmental remediation and energy conversion technologies.

Electronics and Semiconductors: The combination of MLD with ALD is particularly advantageous in the electronics and semiconductor industries. It enables the precise deposition of thin films with tailored electrical and optical properties, crucial for advanced microelectronics and photonics.

Biomedical Applications: The versatility of MLD and ALD-MLD coatings also finds applications in the biomedical field, such as in drug delivery systems and bioimaging, where biocompatibility and controlled interactions with biological environments are essential.

Industrialization and Future Outlook

As for the industrialization of MLD, it is a relatively newer field compared to ALD. While ALD has been widely industrialized, particularly in the semiconductor industry, MLD is still primarily in the research and development stage, with growing interest in transitioning to industrial applications. The unique capabilities of MLD in creating organic-inorganic hybrid materials are driving research and potential industrial applications, but widespread industrial adoption might still be in progress.

Conclusion

The ALD and MLD webinar served as a beacon of knowledge, shedding light on the latest advancements and future prospects of these technologies. As we step into an era where material science plays a critical role in technological advancements, the insights from this webinar not only educate but also inspire further exploration and innovation in the field. The future of material science, undoubtedly, holds exciting possibilities, with ALD and MLD at its forefront.

Background: Topias Jussila is a second year PhD student at the Department of Chemistry and Materials Science, Aalto University, Finland. Topias carried out his Bachelor’s degree in Chemistry at the University of Helsinki and Master’s degree in Functional Materials at Aalto University. For the past two years, Topias has worked intensively with atomic layer deposition (ALD) and molecular layer deposition (MLD) with a target to develop novel thin film materials with advanced functional properties, having the main focus in iron-based inorganic and inorganic-organic materials. In addition to deposition process development, he has employed a wide range of thin film characterization methods to study the composition, structure, and functional properties of the thin films.

Using Vapor Phase Infiltration for Fabricating Membranes with David Bergsman – ALD Stories Ep 11

 

 

From the corner of one continent to another, Professor David Bergsman joins Tyler from the University of Washington in Seattle. David discusses his use of vapor phase infiltration as a method of fabricating new membrane structures inspired by his work in Stacey Bent’s lab at Stanford and how he started an ALD lab during a pandemic. 

In this video: 

00:00 – Introduction 

02:01 – David’s Background & MLD 

08:02 – Membrane Fabrication and Property Challenges 

17:19 – Vapor Phase Infiltration 

37:36 – Starting an ALD lab 

48:30 – Ending & Outro 

Follow Professor David Bergsman on Twitter @DavidBergsman and learn about his research group in Seattle at www.bergsmangroup.com

Area-selective MLD of nylon 6: Growth on carbon and inhibition on silica for a-carbon hardmask repair

Here one of the Editor pic out of the JVSTA Special Topic Collection on Area Selective Deposition. Marcel Junige, is one of Dresden´s top-notch ALD and MLD scientists that went over there to the University of Colorado Boulder to S M Geroge´s famous lab. In this demonstration, it is illustrated the capability of area-selective MLD to repair RIE-eroded aC hard masks and to maintain the critical dimension, which is key in all leading etch semiconductor manufacturing processing schemes. It is a fairly typical situation in this business, the CMP or Etch guys brutally destroy stuff that has to be repaired by ALD or Wet processing, sometimes even by E-Beam single exposure repair. That is maybe one of the drivers behind the more precise and gentle ALE method. Yeah E-CMP ever made it.

Area-selective molecular layer deposition of nylon 6,2 polyamide: Growth on carbon and inhibition on silica

Journal of Vacuum Science & Technology A 39, 023204 (2021); https://doi.org/10.1116/6.0000769
Marcel Junige and Steven M. George

In microelectronic or nanoelectronic manufacturing, pattern transfer by directional reactive ion etching (RIE) progressively erodes amorphous carbon (aC) hard masks. To maintain critical dimensions and tolerances of high-aspect-ratio device structures, new carbonaceous materials may be added repeatedly to replace the eroded aC hard mask. Such a mask repairing step during RIE needs self-aligning growth of organic materials. Area selectivity is required to deposit the organic material on the aC hard mask exclusively. Deposition on the dielectric or semiconductor device structures underlying the mask would complicate their precise etching or later cleaning. When ashing the aC hard mask, all-organic materials are preferable to organic-inorganic hybrid materials because they leave no residue. In this work, area-selective molecular layer deposition (MLD) was developed for the all-organic polyamide nylon 6,2. The monomer reactants for nylon 6,2 MLD were ethylene diamine and adipoyl chloride. Nylon 6,2 MLD was studied in the homogeneous, steady-state growth regime and during nucleation on various starting surfaces utilizing in situ spectroscopic ellipsometry. Area-selective MLD of nylon 6,2 was achieved on the “growth” carbon surface in the presence of silica by functionalizing aC via mild oxidation. In addition, a surface passivant was selectively attached to silica by using an amine-catalyzed coupling chemistry. The passivant inhibited the nylon 6,2 MLD on the “nongrowth” silica surface. A single passivation pretreatment was sufficient to restrict the MLD on the silica surface. The passivant, however, did not substantially impact the MLD nucleation and growth on the aC surface. This strategy yielded area selectivity with exceptionally high quality and over a wide range of MLD cycles. The area-selective MLD of nylon 6,2 was further applied on industrial test features with aC patterns masking trenches in silica. This demonstration illustrated the capability of area-selective MLD to repair RIE-eroded aC hard masks and to maintain the critical dimension.

Molecular Layer Etching of Metalcone Films Using Lithium Organic Salts and TMA

Here is an new important paper on  by reseachers at Argonne National Laboratory, USA. It describes a new technique for the precise removal of metal–organic thin films deposited by molecular layer deposition (MLD), now to be known as term molecular layer etching.

Molecular Layer Etching of Metalcone Films Using Lithium Organic Salts and Trimethylaluminum

Matthias J. YoungDevika ChoudhurySteven LetourneauAnil ManeAngel Yanguas-GilJeffrey W. Elam
Chem. Mater. 2020, XXXX, XXX, XXX-XXX
Publication Date:January 15, 2020
https://doi.org/10.1021/acs.chemmater.9b03627

Advances in semiconductor device manufacturing are limited by our ability to precisely add and remove thin layers of material in multistep fabrication processes. Recent reports on atomic layer etching (ALE) have provided the means for the precise removal of inorganic thin films deposited by atomic layer deposition (ALD), opening new avenues for nanoscale device design. Here, we report on a new technique for the precise removal of metal–organic thin films deposited by molecular layer deposition (MLD), which we term molecular layer etching. This etching process employs sequential exposures of lithium organic salt (LOS) and trimethylaluminum (TMA) precursors to produce self-limiting etching behavior. We employ quartz crystal microbalance experiments to demonstrate (i) etching of alucone films preloaded with LOS upon TMA exposures and (ii) layer-by-layer etching of alucone films using alternating exposures of LOS and TMA. We also identify the selectivity of these etching mechanisms. We probe the mechanism for the layer-by-layer etching of alucone using a quartz crystal microbalance and Fourier transform infrared spectroscopy and identify that the etching proceeds via heterolytic cleaving of Al–O bonds in alucone upon LOS exposure followed by methylation to produce volatile species upon TMA exposure. The etching process results in the removal of 0.4 nm/cycle of alucone at 160 °C and up to 3.6 nm/cycle of alucone at 266 °C in ex situ etching experiments on silicon wafers. This halogen-free etching process enables etching of MLD films and provides new fabrication pathways for the control of material geometries at the nanoscale.

Video Online - HYCOAT Workshop "Hybrid nanocoatings through molecular layer deposition"

Here is a fantastic set of ALD Tutorials & Presentations available on YouTube from a recent HYCOAT event at Ghent University, Belgium August 27-29, 2018 - HYCOAT Workshop "Hybrid nanocoatings through molecular layer deposition (LINK). Please find the YouTube streams below.

HYCOAT Workshop "Hybrid nanocoatings through molecular layer deposition (Picture from Press release LINK)

HYCOAT is a project funded by the European Union in the framework of the H2020 Marie Skłodowska Curie Actions – Innovative Training Networks. It is the first European Training Network at the intersection of chemistry, physics, materials science and engineering dealing with the synthesis and applications of hybrid coatings grown by Molecular Layer Deposition (MLD). On its YouTube Channel, you can find content from the Workshops organized within the HYCOAT training network, as well as information on the research conducted at the participating universities and research institutes.

An introduction to atomic layer deposition (ALD) by Professor Christophe Detavernier, Ghent University, Belgium at the HYCOAT Workshop "Hybrid nanocoatings through molecular layer deposition". (August 27-29, 2018 at Ghent University, Belgium)

Dr. Paul Poodt from TNO, Netherlands, presenting ALD/MLD reactor consepts and design at the "Hybrid nanocoatings through molecular layer deposition" workshop held on August 27th - August 29th, 2018, Ghent University, Belgium.

Professor Adrie Mackus from Eindhoven University of Technology, Netherlands with a lecture on area-selective ALD at the HYCOAT Workshop "Hybrid nanocoatings through molecular layer deposition", held between August 27th and August 29th, 2018 at Ghent University, Belgium.

Professor Mikko Ritala from University of Helsinki, Finland giving an introduction to the chemistry of ALD/MLD precursors at the HYCOAT Workshop "Hybrid nanocoatings through molecular layer deposition", held between August 27th and August 29th, 2018 at Ghent University, Belgium. 

Professor Jess Jur from North Carolina State University, U.S.A. presenting the basics and latest research on atomic layer deposition onto polymers and textiles at the "Hybrid nanocoatings through molecular layer deposition"workshop (August 27-29, 2018, Ghent University, Belgium)

An introduction to diffusion phenomena occuring during atomic layer deposition processing by Professor Mato Knez, CIC nanoGUNE, Spain. Presented at the "Hybrid nanocoatings through molecular layer deposition" workshop held at Ghent University, Belgium from August 27th to August 29th, 2018.

Dr. Karen Leus, Ghent University, Belgium, giving an introduction on properties and applications of metal-organic frameworks and covalent organic frameworks at the "Hybrid nanocoatings through molecular layer deposition" workshop at Ghent University, Belgium.

Workshop on Hybrid Materials by ALD / MLD & Iberian ALD

The workshop on hybrid materials by ALD or MLD on January 23-25 in San Sebastian (Spain) aims at bringing together researchers and industry that are already active or intend to launch activities in this research field. It will serve as a presentation and discussion platform, hopefully sparking new collaborations and business opportunities. In addition to the main scope of the workshop, we will dedicate a session to ALD or MLD activities on the Iberian Peninsula.

 

Co-chairs and local hosts:

• Prof. Mato Knez
• Dr. Mercedes Vila Juárez

Additional local hosts: 

• Itxasne Azpitarte Iraculis
• Mikel Beltrán Hernández
• Julene Lure Berregui

See the website for details:

http://www.nanogune.eu/event/ald-workshop-hybrid-materials

 

Development of safe and durable high-temperature lithium-sulfur batteries by ALD

(From Nanowerk News) Safety has always been a major concern for electric vehicles, especially preventing fire and explosion incidents with the best possible battery technologies. Lithium-sulfur batteries are considered as the most promising candidate for EVs due to their ultra-high energy density, which is over 5 times the capacity of standard commercial Li-ion batteries. This high density makes it possible for electric vehicles to travel longer distances without stopping for a charge. 

 

 

Scheme of MLD alucone coated C-S electrode and cycle performance of stabilized high temperature Li-S batteries. (Figure from Nanowerk News)

Read more: Development of safe and durable high-temperature lithium-sulfur batteries

However, batteries operating at the high temperatures necessary in electric vehicles presents a safety challenge, as fire and other incidents become more likely.

Prof. Andy Xueliang Sun and his University of Western Ontario research team, in collaboration with Dr. Yongfeng Hu and Dr. Qunfeng Xiao from the Canadian Light Source, have developed safe and durable high-temperature Li-S batteries using by a new coating technique called molecular layer deposition (MLD) technology for the first time. This research has been published in Nano Letters ("Safe and Durable High-Temperature Lithium–Sulfur Batteries via Molecular Layer Deposited Coating").


Read more: Development of safe and durable high-temperature lithium-sulfur batteries

Atomic/Molecular Layer Deposition of Lithium Terephthalate for Li-Ion Battery Anodes

EurekAlert.org reports: When microbatteries are manufatured, the key challenge is to make them able to store large amounts of energy in a small space. One way to improve the energy density is to manufacure the batteries based on three-dimensional microstructured architectures. This may increase the effective surface inside a battery- even dozens of times. However, the production of materials fit for these has proven to be very difficult.

Aalto University Researchers testing the material on coin cells. (Mikko Raskinen / Aalto University)

Researches at Aalto University, Helsinki Finland, has develooped a ALD/MLD deposition process for Li-terephthalate, which has been published in Nanoo Letters (below).

- ALD is a great method for making battery materials fit for 3D microstructured architectures. Our method shows it is possible to even produce organic electrode materials by using ALD, which increases the opportunities to manufacture efficient microbatteries, says doctoral candidate Mikko Nisula from Aalto University. (EurekAlert.org)

Atomic/Molecular Layer Deposition of Lithium Terephthalate Thin Films as High Rate Capability Li-Ion Battery Anodes

Nano Lett., 2016, 16 (2), pp 1276–1281

DOI: 10.1021/acs.nanolett.5b04604

We demonstrate the fabrication of high-quality electrochemically active organic lithium electrode thin films by the currently strongly emerging combined atomic/molecular layer deposition (ALD/MLD) technique using lithium terephthalate, a recently found anode material for lithium-ion battery (LIB), as a proof-of-the-concept material. Our deposition process for Li-terephthalate is shown to well comply with the basic principles of ALD-type growth including the sequential self-saturated surface reactions, a necessity when aiming at micro-LIB devices with three-dimensional architectures. The as-deposited films are found crystalline across the deposition temperature range of 200–280 °C, which is a trait highly desired for an electrode material but rather unusual for hybrid inorganic–organic thin films. Excellent rate capability is ascertained for the Li-terephthalate films with no conductive additives required. The electrode performance can be further enhanced by depositing a thin protective LiPON solid-state electrolyte layer on top of Li-terephthalate; this yields highly stable structures with capacity retention of over 97% after 200 charge/discharge cycles at 3.2 C.

Stabilization of ALD barrier film by MLD interlayers by TU Dresden

Integration of molecular-layer-deposited aluminum alkoxide interlayers into inorganic nanolaminate barriers for encapsulation of organic electronics with improved stress resistance

Christoph Hossbach, Frederik Nehm, Aarti Singh, Hannes Klumbies, Dustin Fischer, Claudia Richter, Uwe Schroeder, Matthias Albert, Lars Müller-Meskamp, Karl Leo, Thomas Mikolajick and Johann W. Bartha

J. Vac. Sci. Technol. A 33, 01A119 (2015); http://dx.doi.org/10.1116/1.4901232

Diffusion barrier stacks for the encapsulation of organic electronics made from inorganic nanolaminates of Al 2O3 and TiO2 with aluminum alkoxide interlayers have been deposited byatomic layer deposition (ALD) and molecular layer deposition (MLD). As a part of the MLD process development, the deposition of aluminum alkoxide with low a density of about 1.7 g/cm3was verified. The ALD/MLD diffusion barrier stack is meant to be deposited either on a polymer film, creating a flexible barrier substrate, or on top of a device on glass, creating a thin-filmencapsulation. In order to measure the water vapor transmission rate (WVTR) through the barrier, the device is replaced by a calcium layer acting as a water sensor in an electricalcalcium test. For the barrier stack applied as thin-film encapsulation on glass substrates, high resolution scanning electron microscopy investigations indicate that the inorganic nanolaminates without MLD interlayers are brittle as they crack easily upon the stress induced by the corroding calcium below. The introduction of up to three MLD interlayers of 12 nm each into the 48 nm barrier film laminate successfully mitigates stress issues and prevents the barrier from cracking. Using the three MLD interlayer configurations on glass, WVTRs of as low as 10−5g/m2/d are measured at 38 °C and 32% relative humidity. On polymer barrier substrates, thecalcium is evaporated onto the barrier stack and encapsulated with a cavity glass. In this configuration, the corroding calcium has space for expansion and gas release without affecting the underlying barrier film. In consequence, a WVTR of about 3 × 10−3 g/m2/d is measured for all samples independently of the number of MLD interlayers. In conclusion, a stabilization and preservation of the ALD barrier film against mechanical stress is achieved by the introduction of MLD interlayers into the inorganic nanolaminate.

Schematic drawing of a Ca test built on an ALD barrier coated foil substrate (barrier film test configuration)

Top view of glass Ca tests coated with ALD/MLD barrier stacks consisting of a 48 nm Al-O/Ti-O nanolaminate with zero to three aluminum alkoxide interlayers of 12 nm thickness. The layers were deposited at 90 °C on Ca tests on glass and aged at 38 °C and 32% r.h.—picture taken with high resolution scanning electron microscopy after aging.