For sputtering, the energized particles are present as plasma. Plasma is a partially ionized
gas consisting of positively charged particles (ions), negatively charged particles (electrons and
anions), and neutrals. The overall charge of the plasma is neutral. In the plasma, the ionization
of the gas generally occurs between a cathode and an anode. In a sputtering system the sputtering
target is the cathode. The anode is usually the vacuum chamber wall or the substrate. Within the
sputtering process gas ions are accelerated towards a sputtering target. Material is sputtered from
the target and afterwards deposited on a substrate.