Thin film coating is the process of applying a very thin material onto a ‘substrate’ surface to be coated. It forms different layers and the coating comes through as the technological breakthrough for materials like electronic semiconductor devices or optical coating. Very thin layers of materials are used to develop filters and increase the insulation or conduction. It protects them from light or creates reflective surfaces. The thin films have a minimal thickness, ranging from fractions of a nanometer to several micrometers. Thus, this technology is preferred by a number of industries semiconductor industry, optical device industries, solar panels, and disk drives.
There are different parts in the deposition method which are listed as below–
• Conductive coatings
• Transparent coating
• Metallic coating
• Diamond
• Dielectric thin film coating
There is a host of deposition services for manufacturers seeking to apply thin films, but the ideal method for a given application depends on the purpose of deposition, the surface makeup of the substrate, and the desired thickness. The thin film deposition is basically divided into 2 parts namely chemical or physical and further they have different classifications which will be discussed below.
Chemical Deposition
It is the process by which a substrate is fully submerged in a chemical fluid and then it is deposited onto the surface. It means that every surface of the substrate is coated equally. The most common types of chemical deposition are as follows –
Plating: In this process, a substrate is submerged in a chemical bath, often composed of water mixed with metal salts destined for deposition. They adhere to substrate in a uniform pattern, building up a thicker film. The substrate is connected to an anode powered by an external battery or rectifier.
Chemical Solution Deposition (CSD): It is a process which is similar to plating. But instead of metal salts in a water bath, organometallic powders in an organic solvent carry out the deposition procedure. CSD is cheaper and simpler than plating techniques.
Chemical Vapor Deposition (CVD): It involves a substrate placed in a pressurized chamber full of organometallic gas. The gas either reacts with the substrate surface or slowly dissolves over it, depositing the thin film evenly.
Physical Deposition
It is the technique which does not include chemical reaction and it relies on a mechanical or thermodynamic method for the production of thin films. It requires low-pressure environments for accurate and functional results.
The common types of physical deposition process are as follows–
Thermal Evaporation: In this, the deposition material is melted by an electric resistance heater until the surface of the substrate is covered. A variant of thermal evaporation uses an electron beam evaporator to melt materials on a substrate.
Sputtering: It occurs when a noble gas plasma is shot at a substrate in atom-sized particles. The impact of the particles triggers a collision cascade, which results in particle passing through the substrate.
Pulsed Laser Deposition: It involves a substrate and blocks film material in an ultra-high vacuum chamber. It bursts the light at the block of material which vaporizes and transfers to the substrate facing it.
