In reactive sputtering, what is the phenomenon called in which, with too much reactive gas flow, the target surface becomes covered with a compound and the deposition rate drops sharply?

Answer: A. Target poisoning

In reactive sputtering, increasing reactive gases such as nitrogen or oxygen coats the target surface itself with nitride or oxide. Compounds have low sputter yields, so the deposition rate drops sharply. This is called poisoning; because the deposition rate shows hysteresis with respect to gas flow, control requires care.

• A. Correct. The target surface becomes covered with a compound.
• B. Blooming is charge overflow in image sensors.
• C. Stiction is MEMS movable parts sticking.