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.
Morphological instability and Si diffusion in nanoscale cobalt silicide films formed on heavily phosphorus doped polycrystalline silicon
In this letter we examine the interdiffusion and reaction of deposited cobalt layers during the formation of nanoscale (<35 nm) silicide films on heavily phosphorus doped polycrystalline silicon films. The onset of morphological instability is indicated by an increase of layer resistivity. Cross‐section transmission electron micrographs of high resistance films, which were formed by rapid thermal annealing at 700 °C for 30 s, show a series of disconnected ‘‘islands’’ of CoSi2 with or without a highly disordered (amorphous) Si‐rich top surface layer. A continuous band of voids, attributed to the Kirkendall effect and to phase transformation induced volume changes, initially appear at the CoSi/CoSi2 interface. In the highly agglomerated films, these voids separate the buried CoSi2 islands and buried polycrystalline Si from the disordered surface layer. The sequence of events is analyzed in terms of grain boundary diffusion, grain boundary grooving, and the impact of phosphorus concentration (∼1020 cm−3) on ...
The effect of continuous exposure to low frequency electric fields on three generations of mice: A pilot study
Mice were allowed to mate, gestate, deliver and rear their offspring for 3 successive generations while being continuously exposed to 60 Hz electric fields. Mice exposed to vertical electric fields exhibited decreased body weights at 35 days postpartum and increased mortality, rates for 3 successive generations. Mice exposed to horizontal electric fields exhibited decreased body weights for 2 successive generations.