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  • What is the Thermal Evaporation?

    views, Updated: 2021-09-30

    One of the common methods of Physical Vapor Deposition (PVD) is Thermal Evaporation. This is a form of Thin-film Deposition, which is a vacuum technology for applying coatings of pure materials to the surface of various objects. The coatings, also called films, are usually in the thickness range of angstroms to microns and can be a single material or multiple materials in a layered structure.

    The materials to be applied with Thermal Evaporation techniques can be pure atomic elements, including metals and non-metals, or molecules such as oxides and nitrides. The object to be coated is referred to as the substrate and can be a wide variety of things such as Semiconductor wafers, solar cells, optical components, or many other possibilities.
    Thermal Evaporation involves heating a solid material inside a high vacuum chamber, taking it to a temperature that produces some vapor pressure. Even a relatively low vapor pressure inside the vacuum is sufficient to raise a vapor cloud inside the chamber. This evaporated material now constitutes a vapor stream, which traverses the chamber and hits the substrate, sticking to it as a coating or film.
    In most instances of Thermal Evaporation processes, the material is heated to its melting point and is liquid. It is usually located in the bottom of the chamber, often in some upright crucible. The vapor then rises above this bottom source, and the substrates are held inverted in appropriate fixtures at the top of the chamber. The surfaces intended to be coated, thus facing down toward the heated source material to receive their coating.
    Steps may have to be taken to assure film adhesion and control various film properties as desired. Fortunately, Thermal Evaporation system design and methods can allow the adjustability of several parameters to give process engineers the ability to achieve desired results for such variables as thickness, uniformity, adhesion strength, stress, grain structure, optical or electrical properties.

    Two Primary Means of Heating the Source Material

    One method, often referred to as Filament Evaporation, is a simple electrical resistive heat element or filament. There are numerous different physical configurations of these resistive evaporation filaments, including many known as "boats" - nearly thin sheet metal pieces of suitable high-temperature metals (such as tungsten) with formed indentations or troughs into which the material is placed. The filament source offers low voltage safety, although a very high current is required, usually several hundred amps.

    The other common heat source is an Electron Beam or E-Beam, which is generally known as E-Beam Evaporation. This is certainly a more "high tech" approach to heating a material up and involves some dangerous high voltage (usually 10,000 volts), so E-Beam systems always include extra safety features. The source itself is an E-Beam "gun". A small and very hot filament boils off electrons, which are then accelerated by the high voltage, forming an electron beam with considerable energy.

    AEM Deposition is an international evaporation materials manufacturer. We have over 10 years to produce and sell evaporation materials, including Pure Metal Evaporation Materials, Alloy Evaporation materials, Oxide Evaporation Materials, and Compound Evaporation Materials. All materials are provided with various shapes, pieces, pellets, powder, rods, wires, or others. If you are interested in AEM Deposition's evaporation materials, you can click the link to get more details.