In todays society we depend on the sputtering process not only for the electronics Industry but many other industries as well. When you woke up this morning you probably stood in front of a mirror with a reflective backing which was sputtered. Perhaps you used a razor blade that had a sputtered platinum coating. When you went outside, the sun was bright and you put on sunglasses that had a sputtered coating. The sputtering process is used for other things such as car bumpers, tv and radio knobs, christmas ornaments, and drill bit coatings.
DC metallic sputtering was discovered in 1852 by Sir William Grove, but at that time the process was known as Cathode Disintegration. Cathode Disintegration was a process that changed a gas into a substance later to be called a Plasma. Some 69 years later in 1921 Sir Joseph Thompson redefined the process and called it Spluttering. Two years later in 1923 Sir Joseph Thompson published a technical paper in which the “L” was dropped creating the word Sputtering.
So what is sputtering anyway? SPUTIERING (sputt’-er-ing) as defined by Websters™ dictionary, is to dislodge atoms from a surface of a material (Target or Cathode) by collisions with high energy particles; also: to deposit a film by such a process.
So what is a plasma? PLASMA (Piaz-ma) is the fourth state of matter; a collection of charged particles containing about equal numbers of positive ions and electrons and exhibiting some properties of gas but differing from gas in being a good conductor of electricity and being affected by a magnetic field.
By inducing an electromagnetic field with either DC or RF the primary electron impacts the atom moving the electrons within the atoms orbit to their next highest
orbit (energy level) until a bound electron is ejected out of the atoms orbit producing a positive ion and two electrons.
The two electrons produced by the ionizing collision are accelerated by the electromagnetic field, starting the ionzation process all over again. The ejected positive ion is attracted to the target at a very high speed via a negative potential. As the excited ions collide with the target they will dislodge molecules of the target material which will traverse the chamber and eventually fall on the substrates .
Until now we have only discussed DC plasmas, however in the late 1960′s RF sputtering was discovered expanding deposition to non-metallic substances. RF plasmas are used with targets that have any ratio of non-conductive material to conductive material. Since there is a lack of free electrons within the gaseous argon environment, an igniter is used. The igniter, when charged will spew off many free electrons to ignite the plasma. When the plasma is ignited the igniter will turn off, meanwhile the plasma remains aglow via the potential applied to the target. During the positive swing of the RF sine wave the target is at a positive potential attracting electrons to the target. During the negative swing of the sine wave the target is at a negative potential attracting ions to the target, therefore the sputtering process is started.