Control and Instrumentation > Presentation > Deposition of dielectric thin films RF Magnetron Sputtering MM 731: Experiments in advanced material (All)

Deposition of dielectric thin films RF Magnetron Sputtering MM 731: Experiments in advanced materials processing (Lab.)

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RF (radio frequency) sputter deposition • Good for insulating materials because, positive charge (Ar+) build up on the cathode (target) in DC sputtering systems. Alternating potential can avoid ch... arge buildup • When frequencies less than 50kHz, both electrons and ions can follow the switching of the anode and cathode, basically DC sputtering of both surfaces. • When frequencies well above 50kHz, ions (heavy) can no longer follow the switching, and electrons can neutralize positive charge buildup on each electrode during each half cycle. • As now electrons gain energy directly from RF powder (no need of secondary electrons to maintain plasma), and oscillating electrons are more efficient to ionize the gas, RF sputter is capable of running in lower pressure (1-15 mTorr), so fewer gas collisions and more line of sight deposition. 13.56MHz RF source Switch polarities before the target surface saturates with ions. 2RF plasma • For symmetric target-substrate configuration, sputtering of both surfaces will occur, though in the opposite half cycles. • When the electrode areas are not equal, the field must be higher at the smaller electrode (higher current density), to maintain overall current continuity. • It was found that voltage drop across the dark sheath of the two electrodes satisfy the relation: (A is the area of the electrode) [Show More]

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