Importance of heat-up ramp rate for palladium-silicide fully-silicided-gate structure formation
Silicidation process for fully-silicided (FUSI) Pd2Si gate formation has been investigated. Two types of heating equipment was used for siliciding palladium deposited on a poly-Si/SiO2/Si MOS structure. One is lamp heating in a sputtering chamber and another is hot-plate heating. The former provide slower heat-up ramp because of relatively large thermal capacity. In this case, metal-rich phase was formed in the first stage of silicidation and it changed to Pd2 Si phase by additional heating after completion of silicidation reaction. FUSI utilizes impurity pre-doping to poly-Si to modulate workfunction. Pre-doping to poly-Si sometimes resulted in needle structure formation on a top of silicided film and voids at the interface between silicide and SiO2. These defects were reduced by silicidation with hot plate heating. In addition, Pd2 Si phase was obtained at the early stage of silicidation. Palladium and silicon reacts even at temperatures lower than 250degC. Therefore, in the case of the lamp heating, silicidation during heating is not negligible. These results are explainable considering change of major diffusion species during silicidation
Low-temperature redistribution of As in Si during Pd2Si formation
We have investigated the change in depth compositional profiles of implanted As in Si due to Pd2Si formation by using anodic oxidation and neutron activation analysis. We found that a high concentration (∼1×1021/cm3) of implanted As was snowplowed by the moving silicide‐Si interface into the substrate Si during Pd2Si formation at 250 °C. In other words, we have found a very low temperature process of doping As into Si. The amount of snowplowed As was found to be greater in samples which were preannealed at 900 °C—30 min before silicide formation than those without the preannealing.
EFFECT OF SAMPLE PREPARATION ON WATER TREE RESISTANCE OF XLPE/SEBS BLENDS
The effects of an aromatic polymer, such as poly[styrene-b-(ethylene-co-butylene)b-styrene] (SEBS), and its preparation processes on water tree resistance, morphology, crystallinity, dielectric constant and dielectric loss tangent of crosslinked polyethylene (XLPE)/SEBS and XLPE/SEBS/ethylene vinyl acetate (EVA) blends were investigated. The XLPE/SEBS samples were characterized by means of differential scanning calorimetry, scanning electron microscopy, dielectric spectral analysis and the accelerated water treeing experiment. The results clearly showed that although SEBS was partially compatible with LDPE and it was dispersed evenly in XLPE matrix, the blends demonstrated excellent dielectric performances, such as dielectric constant and dissipation factor. The crystallinity of XLPE/SEBS blends was decreased with increase in SEBS content and it was further decreased with the addition of EVA. SEBS could effectively improve the water-tree resistance of XLPE and both SEBS and EVA were found to improve the water tree resistance of XLPE synergistically as expected. The differences in sample preparation processes could change the phase morphology and dielectric performance of the blends, and could also influence the dispersion of SEBS in XLPE matrix as well as the crystallinity of the blends. Different preparation processes led to different water tree resistance behaviours of the samples. The improvement of SEBS dispersion in XLPE matrix helped to improve the water tree resistance of XLPE.