Over the years, the demand for sputtering targets has increased, followed by a development in coating technology. Sputtering target is a physical vapor deposition (PVD) mechanism that is used to produce thin films. It is an old process that has a lot of modern applications in manufacturing and technology. It was discovered in the year 1852 and in 1920, it was developed as a thin film deposition technique.
The Sputtering Process
The process of sputtering involves the release of atoms in their solid state into a gaseous phase by bombarding them with high-energy ions. In the area of surface physics, sputtering is applied as a method of cleaning to prepare surfaces of top purity. It can also be used for chemical composition analysis of surfaces.
The principle guiding the sputtering process applies plasma energy or energy of partially ionized gas on a target surface or cathode. This will remove the atoms in the material bit by bit and have them deposited on the substrate.
In order for this to happen, a plasma will be created by ionizing Argon gas through electromagnetic excitation (RF, MF) or pulsed DC (potential difference). The plasma which is now made of argon ions will be accelerated and deposited around a target, forming a magnetic field. When the ionized atoms strike the target, they transfer their energy and rip another atom in order to have more energy to transfer to the substrate.
Plasma creation takes place at very high pressure (10-1 to 10-3 mbar). However, it is important to begin the process from a low pressure before Argon gas will be introduced. This is to prevent contamination from residual gases. Sputtering targets can be produced in various shapes such as Delta, rectangular, tubular, and circular. The materials that are used in the production process allows the creation of all kinds of thin layers in one run. This includes alloys.
You can find more useful information on the sputtering process in this article: https://en.wikipedia.org/wiki/Sputter_deposition
Sputtering Target Materials
The table below shows some examples of materials which are used as sputtering targets.
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How are Sputtering Targets Used?
The following are applications for sputtering targets:
1. Decorative Coating
This refers to coating the surfaces of watches, mobile phones, glasses, hardware parts, sanitary ware, and so on. This coating not only beautifies the color of the surfaces, but it also makes them resistant to wear and corrosion.
As peoples’ standard of living keeps improving, more items that are used on a daily basis are expected to have decorative coating. Hence, there is an increasing demand for decorative coating target materials. The major types of materials used in coating are chrome target, stainless steel target, titanium target, tungsten target, nickel target, zirconium target, and tantalum target.
2. Glass Coating
Target materials are applied on glass in order to produce coated glass with low radiation. Coated glass is produced for the purpose of decoration, energy saving, and light control using the principle of magnetron sputtering to splash different layers of film on the glass. Traditional glasses used in old buildings are gradually being replaced by coated glasses. This is because people are now demanding for more ways to save energy, reduce emission, and improve the quality of living.
Consequently, there is an increase in the demand for glass coating target materials. These materials are titanium oxide target, silicon aluminum target, zinc tin target, nickel chrome target, titanium target, chromium target, and silver target.
Additionally, glass coating is being used in the preparation of the rearview mirror of automobiles. This is made by using titanium oxide target, aluminum target, and chrome target. Most automobile manufacturers have moved from the use of aluminum plating process to vacuum sputtering chromium plating process.
3. Coating of Tools
Tools are coated in order to strengthen their surfaces and molds. This can improve their lifespan and the quality of their parts. The target materials that are used in coating industrial tools are titanium target, chromium target, chromium aluminum target, and titanium aluminum target.
4. Coating of Solar Cells
As more people shift focus from fossil fuel to renewable energy, there is an increasing demand for solar panels. Solar cells are the devices which convert solar energy to electricity. They are currently in their 3rd generation. The 1st generation is the monocrystalline solution cell, the 2nd is polycrystalline silicon and amorphous silicon cell, and the 3rd is the thin-film cell.
The sputtering process used in coating solar cells is the preferred preparation technique. The major targets used are copper indium gallium selenium target, cadmium sulphide target, molybdenum target, zinc aluminum target, zinc oxide target, and zinc oxide aluminum target.
Industries where you can find the application of sputtering targets are:
1. Aerospace/defense – to produce heads-up cockpit displays, night vision equipment, jet turbine blades, and mirrors for x-ray and optical telescopes.
2. Automotive – to produce auto trim components, auto headlight and taillights, and drive train bearings and components.
3. Data storage – to produce laser disks, CDs, hard disks, floppy disk, read or write heads, and microelectronic flash memory.
4. Displays – to produce CRTs (cathode ray tubes), CCDs (charge-coupled display devices), Electroluminescent, Flat Panels, Liquid Crystal Displays (LCD), Photoluminescent, Thin Film Transistor (TFT), and Plasma Displays.
5. Electronics – to produce passive thin film components like capacitors and resistors, Surface Acoustic Wave (SAW) devices, Sensors (for chemical composition, temperature, and radiation), and printed circuit boards (PCBs).
As technology continues to advance, the lives of people will keep getting better. Sputtering of surfaces has contributed to the improved quality of life which we enjoy today. Sputtering target has a lot of applications that include energy saving glasses, wrist watches, mobile phones and automobiles.