Keisuke Hayabusa

Copper Bottom-up Deposition by Breakdown of PEG-Cl Inhibition

Copper bottom-up deposition in 200 nm trenches by an acid-copper sulfate with only two additives [poly(ethylene glycol) (PEG) and Cl ] is achieved. The inhibiting effect of electrodeposition by PEG is strongly related to Cl - concentration. Secondary-ion mass spectroscopy measurements show that Cl - is consumed in the electroplating process. The explanation of bottom-up deposition realized in copper superfilling, in which the decrease of Cl - concentration causes rapid electrodeposition on trench bottoms, is verified experimentally.

Preferential Copper Electrodeposition at Submicrometer Trenches by Consumption of Halide Ion

Preferential copper electrodeposition at submicrometer trenches in an acid copper sulfate electroplating bath by addition of only two components [bromide ion and polyethylene glycol (PEG)] is observed. Strong suppression by PEG is observed by the addition of Br - compared with the addition of Cl - . It is supposed that halide ions work as an adhesive between PEG and the copper surface. During electroplating, halide ions are consumed and the concentration of halide ions in submicrometer trenches is reduced by diffusional limitation. The reduction of halide ion concentration weakens the PEG adsorption and thus preferential copper electrodeposition at submicrometer trenches is realized. Nonuniform deposition observed by filling experiments is explained by this model.

Effect of Tensile Stress on Cavitation Erosion and Damage of Polymer

Cavitation erosion tests for epoxy, unsaturated polyester, polycarbonate, and acrylic resin were conducted under various tensile stress conditions (Tensile-Cavitation test). A new testing device was designed to conduct the Tensile-Cavitation test and observe specimen surface during the experiment based on ASTM G32. When tensile stress of 1.31 MPa was loaded on epoxy resin, cracks occurred on the specimen after 0.5 hours during cavitation erosion. When no tensile stress was loaded on the epoxy resin, the damage was general cavitation erosion only. As well as the epoxy resin, unsaturated polyester resin applied tensile stress of 1.31 MPa and polycarbonate resin of 6.54 MPa indicated erosion damages and cracks. When tensile stress of 6.54 MPa was loaded on acrylic resin, the erosion damage was almost the same as the results without tensile stress. We confirmed that anti-cavitation property of epoxy resin was higher than those of acrylic and polycarbonate without tensile stress while the damage of epoxy resin was much serious than that of acrylic resins under tensile stress loadings.

Non-Destructive Inspection of Rebar Corrosion in Concrete Structures by Using BEM and GA

An inverse problem is analyzed where corrosion of rebars is detected from a small number of potential data measured at the surface of concrete structure. Because the shape and number of corrosion in rebars are not known in advance, usual inverse analysis method in which the shape and number of corroded part are assumed is not available. In this research, the genetic algorithm (GA) is employed without any assumption. The fitness in the multi-step GA is defined as the inverse of difference between experimental and numerical potential values, and is evaluated by the boundary element method (BEM). To reduce the computational time, the net elements, which have been recently developed by the authors for corrosion analysis of net structures, is used together with the multi-step GA. It is shown by a simulation that the multi-step GA with net elements are successfully employed in the inverse analysis.

An estimation method of electroplating current densities in LSI fabrication technology by inverse analysis of electric potentials in cells

In this paper, we have developed a novel technique to estimate electroplating current densities from electric potentials in plating cells for LSI fabrication technology. This technique applies inverse analysis process for the estimation. We have also built a device for measuring electric potentials in the plating cell. Measurement experiments under several electroplating conditions were performed to demonstrate the validity of the proposed technique.