Novel Technologies to be Developed for Thin-Film Deposition

A three-year project awarded by the Defense Advanced Research Projects Agency to develop novel technologies for depositing thin films is underway.

The contract award is under DARPA’s Local Control of Materials Synthesis (LoCo) program, which is investigating non-thermal approaches for depositing thin-film coatings onto the surfaces of a variety of materials. The objective of the program is to overcome the reliance on high-thermal energy input by examining the process of thin-film deposition at the molecular component level in areas such as reactant flux, surface mobility and reaction energy, among others.

Many current high-temperature deposition processes cannot be used on military vehicles and other equipment because they exceed the temperature limit of the material. The LoCo program will attempt to create new, low-temperature deposition processes and a new range of coating-substrate pairings to improve the surface properties of materials used in a wide range of defense technologies including rotor blades, infrared missile domes and photovoltaics, among others. Read More

KAMIS manufactures sputtering targets for all sputtering systems in pure metals, alloys, and ceramic materials. 

The Vacuum Process of Thin Film Deposition

The vacuum process of thin film deposition involves the application of coatings of pure materials over the surface of varied and differing objects. The thickness of coatings or films typically possess a range of microns and angstroms and can be of single material or a layered structure of multiple materials. Using quartz crystal monitoring, there are basic principles used to control the thickness and rate of thin film deposition.

The key class of deposition methods is evaporation which involes heating a solid material within a high vacuum chamber in which vapor pressure is produced. A relatively low vapor pressure is adequate to raise a vapor cloud within the vacuum chamber, which is then condensed over surfaces as a coating or film.

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Thin Film Materials

The thin film material market value will grow to $10.25 billion by 2018, at a significant CAGR from 2013 to 2018.

The thin film material market is directly influenced by the growth in the end-user industries, such as photovoltaic solar cells, MEMS, electrical, and others. Owing to the increasing demand for photovoltaic solar cells from both mature and emerging economies, the market promises better growth in the coming years.

Increased government regulations for renewable energy also contribute to the market growth of the photovoltaic solar cells industry.

Europe represents the single-largest market for thin film material for the same period, followed by North America, and Asia-Pacific.

In terms of applications, photovoltaic solar cells, MEMS, semiconductor, electrical and optical coating are major applications of thin film material. Read More

Thin Film Vacuum Coating on Flat Substrates

Vision Flat is an international technology and networking event that celebrates twenty years of research and development in the field of thin-film vacuum coating on flat substrates at the Fraunhofer FEP.

Representatives of leading companies, Corning Inc., Saint-Gobain Glass, Schott AG and experts in this field will highlight recent technological achievements and provide an outlook on future trends. New smart products and the global increasing demand for transparent architecture are posing new challenges to the fabrication and handling of flat materials such as glass, flexible glass and polymers.

The technology session will cover the aspects of large-area, homogeneous, dynamic layer deposition, up-scaling of coating processes, in-line process monitoring, deposition of layer systems via sputtering for architectural glazing, lighting, automotive applications and optics. Read More

Sputtering for Thin Film Deposits

Sputtering process is used in a variety of applications such as flat panel displays, optical discs, automotive and architectural glass, web coating, hard coatings, optical communications, solar cells, semiconductors, magnetic data storage devices, electron microscopy, and decorative applications.

Typical materials used in these applications are Copper, Chromium, Chromium-Molybdenum, Aluminium, Titanium, Aluminium-Titanium, Tungsten, Nickel, Silicon, Indium and Silver, amongst others.

Sputtering process can be used for depositing thin films from a wide range of materials on to different substrates. Although process parameters make sputtering a complex process, they allow a greater degree of control over the film’s growth and structure.

Composition Measure of Thin Films by Sputtering

Secondary Ion Mass Spectrometry (SIMS) is a technique used in materials science to study the composition of thin films and solid surfaces by sputtering the sample’s surface with a focused primary ion beam. In recent years, there has been an increasing interest in studying dopants and contaminants in thin layers near surface in samples, as the device structures get smaller and smaller.

SIMS can be used for examining the elementary composition of the surface as well as near surface region of samples with sensitivity down to parts per billion. In order to get the maximum performance from the device, atmospheric contaminants with low atomic weight such as and oxygen (O), carbon (C), and hydrogen (H) should have low concentration levels.

SIMS: A High Sensitivity Surface Analysis Technique

In SIMS analysis, contamination of hydrocarbons on the surface of the sample to be assessed may produce incorrect results. Hydrocarbons exist abundantly in ambient atmosphere and often deposit on the surface of samples when exposed to air.

During SIMS analysis, the atmospheric contamination on the surface can be embedded into the sample by means of a primary ion beam; this contamination leads to distorted or spurious profiles. Therefore, it is very important for operators to know whether they are determining the surface’s composition or just viewing an artifact caused by contamination. Read More

Gold Coating is a Thin Film of Gold Deposited Onto a Substrate

A gold coating is a very thin film of gold deposited onto a supporting substrate. This serves as a very useful substrate in the life science academia & industrial markets.

  • Typical characteristics of gold surfaces include:
  • Good resistance to oxidation
  • Inert surface for use with biological experimentation
  • Good conductor of electricity
  • Ultra smooth surfaces can be prepared
  • Easily forms thiol chemistry self-assembled monolayers (SAM)

Glossary of Terms

  • Nanometer (nm): 1×10-9 m
  • Ångström (Å): 0.1 nm
  • E-beam Evaporation: A physical vapor deposition technique used for thin film coatings.
  • Adhesion Layer: A thin layer deposited for improving the adhesion of gold on to the substrate (material to be coated).
  • Roughness: A measure of surface smoothness.
  • Grain Size: The size of gold grains present on the surface. Grain size has an effect on the roughness of the gold surface.
  • Self Assembled Monolayers(SAM): Surfaces consisting of a single layer of molecules on a substrate, prepared by adding a solution of the desired molecule onto the substrate surface and washing off the excess.

Physical vapor deposition (PVD) techniques are commonly used for depositing metal thin films onto a surface.

Analyzing Thin Metal Films

Sputtered Neutral Mass Spectrometry is perfect for analyzing thin metal films where composition, thickness and interface condition can be determined. The example presented here, shows a magnetic film stack comprising Cr, Ni, Cu and Fe. Of the different methods of data storage, magnetic hard discs still offer highly economic means for high density rapid access. The continual move towards more and more compact read/write heads and more closely spaced data tracks has lead to a considerable development of magnetic materials and structures for this demanding application. Analysis of the metallic layer structures used in magnetic data storage is vital for both development and quality management with secondary ion mass spectrometry (SIMS) and sputtered neutral mass spectrometry (SNMS) offering information on minor and major element composition respectively.

SIMS and SNMS

Both SIMS and SNMS use a concentrated, mono- energetic, chemically pure ion beam of typically 1-10 keV to sputter erode the surface under study. A small fraction of the sputtered material gets ionized due to the sputtering process itself and in SIMS, it is these ions that offer the sensitive information for which the technique is known. Being a mass spectrometry technique, all elements and isotopes may be detected, and in favorable conditions the detection limit can be in the low ppb region. However, because the ionization mechanism for SIMS takes place at the sample surface, it is very much dependent on the local chemistry and the ionized fraction can vary by several orders of magnitude. This makes SIMS ideal for trace analysis in materials of known matrix but quantification in materials of changing matrix can be complicated. SNMS overcomes the “matrix effect” by separating the sputtering and ionization events.

New Sputtering Target Innovations

Magnetron sputtering was initially developed using metal or alloy targets with materials having high electrical conductivity (e.g., Al, Ag, Au, Cu, Ti, Mo, etc.). In order to achieve acceptable deposition rates, the target material needed to be electrically and thermally conductive. Ceramic targets were developed for transparent conductive oxides (TCOs) and usually consisted of films made from compositions of ZnO:Al2O3 (2% wt) or In2O3:SnO2 (10% wt). However, as the name implies, the materials were fairly conductive and were suited for DC magnetron sputtering.

Pulsed-DC and RF magnetron sputtering allows for the deposition of materials with poor electrical conductivity. Semiconductor materials with better electrical conductivity can be sputtered with pulsed-DC power supplies, while insulating materials (mainly ceramics) require RF sputtering. The deposition rates for RF sputtering are generally much lower than with pulsed-DC. Also, pulsed-DC sputtering has a lower deposition rate than DC sputtering. New applications in photovoltaic, thermoelectric, storage, and semiconductor markets are spurring innovation in ceramic and semiconductor sputtering targets.

DC sputtering with metallic targets has fewer process problems since the metals are ductile and the materials feature high conductivity. Conversely, semiconductor and ceramic targets are more prone to process difficulties due to the brittle nature of the materials and the poor electrical and thermal conductivities. In order to achieve consistent sputtering over the life of the target, it is essential to have a well-sintered target material with high density. Voids and cracks in the material can propagate and lead to sputtering problems such as arcing, target cracking, and particle generation. Read More

Successful Large-Area Sputtering

Cylindrical rotating magnetrons can provide controlled reactive sputtering on both large areas and high-volume products, while also minimizing arcing and anode problems.

Magnetron sputtering, combined with an accurate control of process parameters and layer quality, has become one of the most important methods for depositing thin films. The technique involves bombarding a target surface, which is positioned on a magnetic tube, with an ionized gas. The gas causes metallic atoms to be ejected from the target and subsequently deposited on the substrate to be coated. In standard metallic sputtering, an inert gas, such as argon, is used. No chemical reaction occurs between the gas and the target particles, resulting in a coating on the substrate with a composition similar to the target material.

In a reactive sputtering process, at least one reactive gas (e.g., oxygen or nitrogen) is added. The reactive gas enhances the sputtering process on the target surface and also generates a chemical reaction with the target particles, forming a compound layer on the substrate. As a result, high-purity, uniform coatings can be achieved. Read More