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Sputtering is a process of thin film deposition in which a solid target material is ejected onto the surface of a substrate to form a thin coating. A sputtering system is a machine in which a sputtering process occurs. It contains the entire process and allows a user to adjust the temperature, power, pressure, target, and substrate materials.
Sputtering is known as physical vapor deposition, because the thin film is formed by physical means, rather than through chemical reactions. In a sputtering system, a vacuum chamber contains the target material, a power source, and a gas plasma. The gas, which is usually a noble gas such as argon, is brought into the chamber at a very low pressure to start the process.
The power source generates electrons that bombard the gas plasma, and these electrons kick away other electrons present in the gas. This causes the gas to ionize and form positive ions known as cations. These cations in turn bombard the target material, knocking away small pieces of it that travel through the chamber and deposit themselves on the substrate. The process is easily perpetuated in the sputtering system chamber, because extra electrons are freed during the ionization of the gas plasma.
Sputtering systems vary in terms of structure, power source, size, and price. The orientation of the target material and substrate are specific to each machine. Some systems will face the target material parallel to the surface of the substrate, while others will tilt either surface to form a different deposition pattern. Confocal sputtering, for example, orients multiple units of target material in a circle pointing toward a focal point. The substrate in this type of system can then be rotated for more even deposition.
The power source also varies, because certain systems use direct current (DC) power, while others use radio frequency (RF) power. One type of sputtering system, known as magnetron sputtering, also includes magnets to stabilize the free electrons and even out the thin film deposition. These methods give the sputtering system different qualities regarding temperature and speed of deposition.
Sputtering systems range in size from desktop systems to large machines that are bigger than a refrigerator. The inner chamber also varies in size, but is generally much smaller than the machine itself; most chambers have diameters smaller than 1 yard (about 1 meter). The cost of a sputtering system ranges from less than $20,000 US Dollars (USD) used, to upward of $650,000 USD for a new or custom designed system.
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