The use of concentrated hydrogen peroxide as an agent which etchesTiW is well known in the metals industry. Although hydrogen peroxide isused in most semiconductor manufacturing processes, its' application asan etchant for TiW has been limited. Since some Micro-Rel product uses acomposite metallization scheme containing a TiW/AlSiCu/TiW sandwich, thebonding pad etch process must include a TiW removal step. Without thisstep, a residual TiW layer is left on the metal pads causing wireadhesion problems (non-sticks) during the wire bonding processes.Current plasma etch techniques still leave a TiW residue on the aluminumsurface. The hydrogen peroxide clean was instituted to minimize thepresence of the TiW residue. By inserting this clean as the last step ofthe pad masking module, a cleaner metal surface was developed. To testthe new process, wire pulls were done on product by two separatebusiness units within Medtronic. Results from both areas showed nolifts. Surface analyses of metal bond pads treated with hydrogenperoxide shows a significant decrease in the concentrations of metallicoxides and tungsten. The SEM images of bonding pads show no loss inmetal thickness and the metal surface is relative smooth with no traceof TiW visually evident
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