FOCUSED ION-BEAM MILLING TECHNOLOGY FOR ON-CHIP WIRING MODIFICATION SYSTEM FOR LSI

During debugging logic LSIs, the period to reproduce LSI in order to c hange the logic design is becoming longer. To reduce the period from s everal weeks down to one day, an on-chip direct wiring modification sy stem, using the focused ion beam (FIB) milling and the laser CVD, has been developed. This paper describes a precise FIB milling technique f or cutting the wirings and making the via holes to the wirings of the LSI. Milling depth control by monitoring the ion induced photo-emissio ns and a milling strategy to overcome the surface steps of the LSI res ulted in a milling depth accuracy of +/-0.25 mu m. The system, consist ing of the FIB milling described in this paper and the laser CVD, has been applied to the logic modification of the LSIs of the Hitachi M880 mainframe computer. Several tens of cuts and via holes on a LSI chip were made by FIB, and several jumper wirings were made by laser CVD. A n average yield of modified LSI chips of 91.8% was achieved.