Thin Films Deposited by Bias Sputtering

Abstract

The application of a suitable negative bias to a film that is being deposited by dc sputtering produces a film of substantially lower resistivity (than without bias). The action of the bias is shown to result from positive ion bombardment of the film during deposition, leading to the selective removal of adsorbed impurities. An analytical expression describing the process is derived and found to give good agreement for tantalum films sputtered in argon containing oxygen as a contaminant. The effect of bias on contaminants originating both at the cathode and in the gas is compared. Comparison of bias sputtering and asymmetric ac sputtering in terms of an ion bombardment model shows that bias sputtering leads to purer films because ion clean-up is in operation during the entire deposition time only for the case of bias sputtering. Good adhesion of bias-sputtered Ta films to glass substrates is obtained by initially applying a small positive bias to the substrate.

Alpha- vs. beta-W nanocrystalline thin films: A comprehensive study of sputter parameters and resulting materials' properties

“…This incorporated, closed porosity, however, explains the deviation of the film properties from those prepared with lower substrate bias, especially increased resistivity and severely reduced mechanical performance. A similar behavior regarding the effects of substrate bias on film resistivity was reported elsewhere, regarding high pressure depositions [32].…”

“…Only depositions at higher bias voltages show an elevated resistivity, albeit, they remain at roughly the same order of magnitude. A drop in resistivity in the low pressure regime, as reported in literature [32], was not observed.…”

“…Prior to thin film deposition, the chamber was prepared by a bakeout for 10 h at 120°C and by sputtering of Ti into the empty chamber Thin Solid Films 577 (2015) [26][27][28][29][30][31][32][33][34] (at least 2 min, 200 W, 0.67 Pa) to reduce residual hydrogen and oxygen contents. The resulting base pressure was better than 4.533 · 10 −7 Pa (3.4 · 10 −7 Torr).…”

Empirical-Statistical Study on the Relationship between Deposition Parameters, Process Variables, Deposition Rate and Mechanical Properties of a-C:H:W Coatings

“…This indicates that neither resputtering [38] nor compaction mechanisms caused by energetic ions play an important role, nor are being compensated by enhanced reactive film growth at the substrates. This is in general agreement with the findings of Pujada and Janssen [12] that, depending on the ethine flow rate, the density of reactively-sputtered a-C:H:W is not or only weakly increased if the bias voltage is elevated from 0 to 140 V.…”

Preparation Methods for Thin Films

“…Bias Sputtering (31) In the systems so far discussed, the substrate has either been floating electrically or kept at anode potential. It is, however, possible to give the film, assuming it is conductive, a small negative bias relative to the anode.…”