Development andImplementation ofC4NPTechnology for300mm Wafers

Considerable workisongoing worldwide ondeveloping lead-free solutions forelectronics industry tomeettheneeds ofRoHsrequirements. Thispaper describes thedevelopment andimplementation oflead-free C4interconnects for300mm wafers using, C4NPtechnology atIBM withequipment partnership withSussMicroTech Inc.Keyprocess modules ofC4NPtechnology are:(a)UBM padsfabrication using simple unit processes inbackendoftheline semiconductor manufacturing facility, (b)Solder meltfilling ofglass molds withcavities insolder fill tool andinspection, (c)C4bump transfer toUBM padsonwafers using vaporized flux process insolder transfer tool, (d)Final inspections andelectrical tests. Thisprocess technology forC4bumping eliminates the needforsolder orsolder alloy plating andprovides wider latitude forselecting solder composition. Forexample, solders canbeselected forimproved mechanical properties and,orlowalphaemission requirements. Thiscanbe accomplished bysimple changing ofmoldfill head. Primary efforts ofthisstudy arefocused onfourkey elements: (1)Development ofunit processes forUBM pad patterning andsolder transfer processing, (2)Chip/organic laminate modulebuilds, using industry standard bondand assembly processes, (3)Selection ofspecific testvehicle wafers with200um pitch padsandover1.25million C4 bumps, and(4)Extensive reliability testing ofmodules with JDECandIBMinternal standards. Modules withtest vehicle chips aswellasproduct chipshaveshownexcellent reliability data, comparable tothat ofhighleadelectroplated C4bumpsl11, andmeetapplication requirements. Inorder to assessmanufacturing robustness and yields, sector partitioning studies wereundertaken tounderstand theeffects ofunit process windows anddefect densities. Results show that C4NPtechnology canproduce yields comparable tothat ofelectroplated C4Bumps.Technology qualification studies havebeensuccessfully completed. Thus, enabling thepath formanufacturing rampup.Thistechnology isextendable to higher density C4 interconnects andproduct qualifications studies onC4bumpson150um pitch areongoing. IBM is adapting this technology for300mm lead-free applications.