Reduction of pumping time for a sputtering system by glow discharge cleaning

Abstract

Sputtering systems for semiconductor manufacturing require high-vacuum conditions. Typically it takes a long time to recover high-vacuum conditions after a sputtering system is opened to air. To increase the operating efficiency of the system, the recovery time must be reduced. Therefore, in this study, a glow discharge cleaning technique is applied using a glow-mode plasma source in argon gas. The discharge current distribution inside the sputtering system is measured under various conditions. It was found that nonuniformity was decreased: when the number of electrodes was increased from one to two; when the pressure during the discharge was decreased to 3×10−3 Torr; and when the anode current or anode voltage was increased. By applying these results, a drastic reduction in pumping time is achieved. The pumping time to attain a pressure of 1.5×10−6 Torr is reduced from 17 to 6 h with concurrent use of 3.5 h of discharge cleaning.

Experimental results of a dc glow discharge source with controlled plasma floating potential for plasma immersion ion implantation

“…In our work, we focused our efforts on eliminating the etching process because, in order to reduce the time of exposure to PIII processing, a much faster high-voltage pulser would be required in contrast to our homemade one. Adding a simple hot filament to the discharge above and varying the electrons emitted by the filament it was possible to start the discharge more easily [4] and vary the floating potential from 0 up to 350 V near the sample holder region. Under these conditions, the temperature of the plasma did not change significantly from the previous case (T e < 10 eV) while the density varies almost linearly with the floating potential as can be verified in figure 2.…”

“…Using a hot filament together with the dc glow discharge it is possible to reduce the work pressure, since the electrons emitted by the filament make it easier to start and to keep a stable discharge [4]. Also, by varying the power delivered to the filament, it is possible to control the floating potential which, if kept below 70 V, results in a dramatic reduction of the etching of the sample's surface and consequently successful PIII ion implantations with high doses are possible using such a plasma source.…”