DC diode sputtering of titanium: determination of optimal deposition conditions by electrical and spectroscopic investigations

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Abstract
An argon DC glow discharge in a diode sputtering system fitted with a titanium cathode is investigated. The first results fix the boundaries of good working conditions for the discharge; mathematical relations are established for the pressure range 40-120 mTorr, anode-cathode lengths from 15 to 60 mm and current densities from 0.6 to 2 mA cm-2. The deposition rate is found to be proportional to the electrical power if the product pd is kept constant, but the ratio of the deposition rate to discharge power exhibits a maximum for d approximately=1.5 le. Spectroscopic studies of the discharge close to the substrate surface show that the intensity of some arc and spark lines of titanium is also proportional to the deposition rate. Emission spectroscopy shows that hydrogen is produced and quickly pumped during the presputtering stage; its evacuation is necessary to obtain good metallic films.