Glass substrate cleaning using a low energy ion source

Characterisation of hard disk substrates before and after heating using X-r ay, photoelectron spectroscopy (XPS) has shown that organic surface contami nation cannot be removed totally by only using a standard heating process. First, studies of an ion source with ion energies of up to 350 eV have give n strong evidence that this method is a suitable candidate to achieve a bet ter surface cleaning. The work described here concentrates on the investiga tion of the carbon etch rates for this source operated with Ar, O-2 and Ar/ O-2 mixture gas and on the ion bombardment-induced topographical surface mo difications of the glass substrate. The used DC glow discharge-based multi cell ion source was adapted to a hard disk production sputter system. The p ower vs. voltage characteristics of this source were measured for the diffe rent discharge gases. Carbon films have been prepared on glass-substrates u sing a magnetron sputtering source. Carbon etch rates were measured using o ptical density change of the thin carbon films which has shown to be a line ar function of the film thickness in the investigated range. The carbon etc hing rate increases almost linearly with discharge power. A higher oxygen g as flow also leads to a linear increase in etching rate. Using different O- 2 percentages in the discharge gas shows that more oxygen causes a signific ant enhancement of the carbon etch rate. For all discharge parameters etch rates have been measured as a function of the position on the disk substrat e. Etching-induced topographical surface modifications have been investigat ed using atomic force microscopy (AFM). Etching of the glass substrate lead s to a reduction of the mean roughness of the surface. This is similar to t he etch modifications on NiP-plated Al substrates which are also used for h ard disk production. (C) 2001 Elsevier Science B.V. All rights reserved.