The ALD workshop with tutorial and industrial exhibition "ALD for Industry" took place for the seventh time in Dresden in March 2024. More than 100 participants visited Dresden to learn about the basics, new aspects of research and development as well as current or planned industrial applications in the field of atomic layer deposition (ALD), to exchange experiences or to prepare the transfer to application and commercialization.
A tutorial preceding the workshop provided information on the fundamentals of the ALD process, process development, analytical methods for process characterization, atomistic simulation of ALD processes and the precursors used. The workshop offered an overview of the state of the art and the expected further development of ALD technology in numerous contributions.
At the industrial exhibition held parallel to the workshop and tutorial, competent institutions presented ALD tools, components, systems and precursors, among other things. This made it easy for participants to find out about new products and services during the breaks.
The ALD process
Atomic layer deposition (ALD) is a process with which a large number of extremely thin layers can be deposited in the monomolecular range. It is a chemical vapor deposition (CVD) process with cyclic self-limiting surface reactions. The reaction partners, called precursors (gaseous, liquid or solid), are transferred into the gas phase and then fed into the reaction chamber one after the other, alternately. The reaction takes place directly on the surface of the substrate to be coated. Excess reactants are removed from the reaction chamber by a rinsing step. The next cycle can begin. The resulting layers usually have a polycrystalline or amorphous structure.
The Spatial ALD process
In conventional ALD, a stationary component is exposed to the various reaction gases one after the other, which takes time. In spatial ALD, on the other hand, the product moves through various shielded gas zones. Spatial atomic layer deposition (Spatial ALD) is a shape-following, high-quality coating method at the atomic level. Compared to conventional ALD, it can also be used to produce complex multilayer coating systems efficiently and cost-effectively. Maximum throughput at the lowest possible cost, improved functionality, efficiency and sustainability, material reduction and longer service life are the added values that Spatial ALD brings.
Applications for ALD processes are emerging in many areas, from microelectronics and battery technology to photovoltaics, optics, lighting technology, biomedicine and quantum technology. In the field of coating technology, protective layers or decorative coatings can be produced on a customized basis.
The lectures
The evening event in Dresden's Sophienkeller provided an opportunity to cultivate contacts and exchange information (Photo: EFDS e.V.)Selected presentations focusing on surface technology are briefly presented below. In her presentation "Green ALD - A guide to a better practice using an LCA approach", Houyem Hafdi, Linköping University, Sweden, addressed the environmental compatibility of ALD processes. Only 10 % of the precursors used are used for layer formation. Furthermore, vacuum is required and the reactor must be heated. With the help of Life Cycle Assessment (LCA), the potential impact on the environment and resources of a product or process can be recorded and optimized. This was demonstrated using the example of the deposition of gallium nitride (GaN).
"Scaling ALD for optical coatings using DC-plasma and a novel method for precursor separation" - Eric Dickey, Lotus Applied Technology, USA, presented a method for separating the metal-containing precursor from active radicals. Oxygen radicals are neutralized on the way from the plasma zone to the precursor area using a compact protective screen around the plasma source. Only the plasma is pumped in the direction of the precursor. For some of the most common optical coating materials (SiO2, Nb2O5, TiO2, Ta2O5, HfO2, ZrO2), deposition rates of 2-6 Å/s, sometimes even over 10 Å, can be achieved. Lenses curved in the centimeter range can also be coated. Multiple plasma shield sources facilitate the implementation on an industrial scale and the coating of large-area parts.
"From Nano to Micro - when ALD meets with PVD to enhance coating performance" - Carlos Guerra, Swiss Cluster, Switzerland, showed how the two process technologies ALD and PVD can be combined in a novel way. The SC-1 system can deposit complex coating systems of up to several hundred individual layers. This results in a variety of customized coating systems made of lighter and more cost-effective materials with improved mechanical and thermal properties. This was demonstrated using the example of a metal-ceramic layer consisting of 200 nanolayers with increased hardness and tensile strength.
"Application of very thin coatings on different grades of particles by ALD" - Mario Krug, Fraunhofer IKTS, Germany, showed in his presentation that ALD is the optimal method to functionalize "extremely three-dimensional" particles in micrometer size or smaller. In order to achieve a homogeneous coating in a short time, the particles must be moved, e.g. in a drum. At IKTS, a suitable apparatus was manufactured and optimized on a laboratory scale. The measures investigated were able to prevent the powder from caking and achieve a uniform coating. There are applications for functionalized powders in many areas, including electromobility (for batteries) and pharmaceuticals (for drug delivery).
"Mechanical model materials with ALD, MLD and PVD" - Ivo Utke, Empa, Switzerland, reported on work on the synthesis of layers and structures with tailored and optimized properties such as toughness, tensile strength and adhesion. Stress/strain curves showed that in some cases an increase in tensile strength of 20 % was possible. A combination of MLD (molecular layer deposition) and ALD (atomic layer deposition) made it possible, for example, to produce metallic cone structures (metal cones) from aluminum. Another example was ultra-fine aluminum powders with very uniform size distribution and shape produced by PVD/ALD.
"In-situ gas monitoring of ALD processes using remote optical emission spectroscopy" - Erik J. Cox, Gencoa Ltd, UK, presented a sensor for measuring gas concentrations during the ALD process. It operates in the pressure range from 10 to 4 mbar, prevents contamination of the sensor electrodes and increases the measurement accuracy of the precursors and their reaction products without influencing the ALD process itself. The sensor generates a plasma in which the species to be measured are excited using optical emission spectroscopy (OES). They then emit a light spectrum with which they can be identified and measured. Using examples such as the detection of impurities, the optimization of the time for rinsing processes and the recording of reaction dynamics, the speaker was able to demonstrate the advantages of this measurement method.
The next "ALD for Industry" conference starts on March 11-12 in Dresden
