IBM System z9 eFUSE applications and methodology

IBM System z9TM is the first zSeries® product to use electronic fuses (eFUSEs). The blowing of the fuse does not involve a physical rupture of the fuse element, but rather causes electromigration of the silicide layer, substantially increasing the resistance. The fuse is "blown" with the application of a higher-than-nominal voltage, eFUSEs provide several compelling advantages over the laser fuses they have replaced. The blow process does not risk damage to adjacent devices, eFUSEs can be blown by a logic process instead of a physical laser ablation method, eFUSEs are substantially smaller than laser fuses, and they scale better with process improvements. Finally, since no specialized equipment or separate product flow is required, eFUSEs can be blown at multiple test and application stages. We discuss circuit design, fuse programming, test considerations, and z9TM system applications. The physical and logical implementation of eFUSEs has resulted in improved yield at wafer, module, and final assembly test levels, and has provided additional flexibility in logic function and in system use.