Suppression of cobalt silicide agglomeration using nitrogen (N/sub 2//sup +/) implantation
In this paper, the effects of nitrogen coimplantation with boron into p/sup +/-poly gate in PMOSFETs on the agglomeration effects of CoSi/sub 2/ are studied. The thermal stability of CoSi/sub 2//poly-Si stacked layers can be significantly improved by using nitrogen implantation. Samples with 40-nm cobalt silicide (CoSi/sub 2/) on 210-nm poly-Si implanted by 2/spl times/10/sup 15//cm/sup 2/ N/sub 2//sup +/ are thermally stable above 950/spl deg/C for 30 s in N/sub 2/ ambient. If the dose of nitrogen is increased up to 6/spl times/10/sup 15//cm/sup 2/, the sheet resistance of CoSi/sub 2/ film is not increased at all, and TEM photographs show that the agglomeration of CoSi/sub 2/ film is completely suppressed.
Interfacial reactions and microstructural evolution of periodic Ni nanodot arrays on N2+-implanted amorphous Si substrates
Abstract We report here on the results of a systematic investigation of the interfacial reactions and microstructural evolution of nanoscale Ni metal dots on N 2 + -implanted amorphous Si (a-Si) substrates under different annealing conditions. During annealing, Ni 2 Si was the first phase to form, followed by NiSi and NiSi 2 . The three Ni-silicide phases formed were polycrystalline and the average sizes of the annealed nanodots were observed to increase with the annealing temperature, up to 500 °C. After a further increase of the annealing temperature and/or time, it is interesting to note that the NiSi 2 grains gradually migrated outward from their original nanodot positions to the a-Si regions, which resulted in the formation of a remarkable NiSi 2 nanoring structure. The inner regions of the NiSi 2 nanorings were found to be comprised of a single crystalline Si phase, indicating mediation of the epitaxial crystallization of N 2 + -implanted a-Si by the lateral migration of the NiSi 2 nanodots. Furthermore, the annealing temperature required for complete recrystallization of the a-Si layer in the Ni nanodot/N 2 + -implanted a-Si sample could be significantly reduced to 550 °C, 200 °C lower than that which was required the blank N 2 + -implanted a-Si sample. It is suggested that the formation of these remarkable NiSi 2 nanoring structures and the enhancement of N 2 + -implanted a-Si recrystallization in the presence of NiSi 2 nanodots were due to the silicide-induced crystallization mechanism.
Fungal Biotransformations in Pharmaceutical Sciences
The regio- and stereoselective conversion of complex substrates represents one of the major advantage of microbial biotransformation. This chapter covers the biocatalytic capacities of fungi to derivatize bioactive small molecules, both from natural sources and from synthetic compounds. We focus particularly on sterol and taxane biotransformation. We also present examples at the interface of biotransformation and pathway engineering using recombinant organisms, with an emphasis on the production of lovastatin derivatives. Finally, we highlight selected studies on fungal xenometabolism which serves as a model to study the breakdown of drugs in mammals.