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DC-Hydrogen Plasma Cleaning a Novel Process for IC-PackagingNico Onda 1, Zeno Stössel 1, Alex Dommann 2 and Jürgen Ramm 3 AbstractAn advanced plasma cleaning process which differs from conventional plasma cleaning has been used for cleaning of organic and metallic chip carrier prior to gold-ball wire bonding. The plasma process is based on an argonhydrogen discharge generated between the heated filament (cathode) and the chamber walls (anode). The discharge is characterized by high currents from 10 A to 100 A and low voltages of 20-30 V, which allows a soft and very efficient cleaning by chemical reactions only and avoiding sputtering of material. The plasma chemistry has been investigated in-situ by plasma process monitoring of copper substrates. \/olatile hydrogen compounds are formed during cleaning, which then are pumped away. The plasmatreated surfaces have been analyzed in-situ by Auger electron spectroscopy. The effect of plasma cleaning on substrate potential (grounded, floating and biased potential) has been investigated in view of cross contamination, substrate heating and plasma penetration into magazines. The role of hydrogen and oxygen as cleaning gases is discussed with respect to the cleaning efficiency and the long-term cleaning effect. The effect on wire bondability has been examined by shear and pull force measurements. The investigations clearly show that this simple and environmentally friendly process is an effective method to reduce organic and some inorganic contamination. No particular plasma process optimization or cleaning control is required if hydrogen is utilized as a process gas. The effect of plasma treatment results in drastic improvement of the wire bondability and reliability.
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