Akira Shimase

Monte Carlo Simulation of Energetic Ion Behavior in Amorphous Targets

A Monte Carlo calculation procedure for simulating the scattering processes of an energetic ion in amorphous targets is given. This computer program can be extended to any ion-target combination up to several MeV incident energy. A high degree of simulation accuracy is obtained independently of incident energy within a reasonable amount of computer time at high as well as low incident energies. Good agreement is obtained in the comparison with calculated depth distributions for implanted ions with the experiments and other Monte Carlo results.

Condensation of bombarding gallium ions on a silicon surface

Direct observation of bombarding 5–15‐keV Ga+ ion condensation on a Si target is achieved using a scanning ion microscope with a liquid‐Ga ion source. The liquidlike pieces of condensed Ga move about easily to join or split. Condensation takes place beyond a critical ion dose, which is roughly explained by an implanted‐ion build‐up model.

Carbon Needle Emitter for Boron and Aluminum Ion Liquid-Metal-Ion Sources

A long-life glassy carbon needle emitter for a boron liquid-metal-ion source utilizing NiB alloy is developed. A lifetime (i.e. 50–90 hours) is achieved. The nickel coated carbon emitter is found also to be useful with an aluminum liquid-ion source.

Cutting of conductors on VLSI chips — A comparison between laser and focused ion beam removal

Abstract A comparison was made between laser evaporation-explosion and focused ion beam (FIB) sputter etching for cutting of conductors on VLSI chips. In laser cutting, thin film layers underlying the conductors and the neighboring area are liable to be damaged because of its evaporation-explosion mechanism. FIB etching has not only a submicron focusing ability but also little material dependence in its etching characteristics. Therefore, FIB cutting is more advantageous for applications to fine pattern and multilayer conductor systems in VLSIs. Under these considerations, FIB conductor cutting was successfully carried out for VLSI circuits debugging, and the effectiveness and usefulness of FIB cutting were demonstrated.

Focused Ion Beam Milling Technology for On-chip Wiring Modification System for LSI.

During debugging logic LSIs, a period to reproduce LSI in order to change the logic design is becoming longer. To reduce the period from several weeks down to one day, an on-chip direct wiring modification system, using the focused ion beam (FIB) milling and the laser CVD, has been developed.This paper describes a precise FIB milling technique for cutting the wirings and making the via holes to the wirings of the LSI. Milling depth control by monitoring the ion induced photo-emissions and the milling strategy to overcome the surface steps of the LSI resulted in the milling depth accuracy of ±0.25μm. The system, consist of the FIB milling described in this paper and the laser CVD, has been applied to the logic modification of the LSIs of Hitachi M880 mainframe computer. Several tens of cuts, vias on an LSI chip were made by FIB, and the several jumper wirings were made by laser CVD. The average yield of modified LSI chips of 91.8% was achieved.