• Journal of the Korean Ceramic Society
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• v.33 no.9
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• pp.1012-1018
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• 1996

To investigate the final structures and reactions of silicides a somewhat thick Ti monolayer Co monolayer and Co/Ti bilayer films were deposited on single Si(100) wafer by electron beam evaporation followed by heat treatment using RTA system in N2 ambient. TiO2 film formed between Ti and TiSi2 layers due to oxgen or moisture in the Ti monolayer sample. The final layer structure obtained after the silicidation heat-treatment of the Co/Ti bilayer sample turned out to be TiSi2/CoSi2/Ti-Co-Si alloy/CoSi2/Si sbustrate. This implies that imperfect layer inversion occurred due to the formation of Ti-Co-Si intermediate phase.

• Journal of the Korean Vacuum Society
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• v.7 no.3
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• pp.208-213
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• 1998

Silicidation of the Co/Ti/Si bilayer system in which Ti is used as epitaxy promoter for $CoSi_2$has recently received much attention. The Co/Ti bilayer on the spacer oxide of gate electrode must be thermally stable at high temperatures for a salicide transistor to be fabricated successfully. In the $SiO_2$substrate was rapid-thermal annealed. The Sheet resistances of the Co/Ti bilayer increased substantially after annealing at $600^{\circ}C$, which is due to the agglomeration of the Co layer to reduce the interface energy between the Co layer and the $SiO_2$substrate. In the bilayer system insulating Ti oxide stoichiometric Ti oxide and silicide were not found after annealing.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.11
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• pp.105-111
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• 1996

We have invetigated the characteristics of thermal instability of Co-silicides annealed at 850$^{\circ}$C ~ 1000$^{\circ}$C for 10~90 minutes in a furance with N$_{2}$ ambient. In our experiments, Co-silicides and Co/Ti bilayer silicides were formed by depositing (Co, Ti) films on the clean Si substrates in an E-beam evaporator and performing the RTA annelaing. The sheet resistances of Co-silicides formed form Co exhibited the nearly constant value under the post-annealing time above 900$^{\circ}$C showing the increase of 30% and 60% under the conditions annealed at 900$^{\circ}$C and 1000$^{\circ}$C for 30minutes. On the other hand, there were no remarkable changes in the sheet resistance sof Co-silicides formed form Co/Ti bilayer under the post-annealing conditons below 1000$^{\circ}$C.

• Korean Journal of Materials Research
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• v.9 no.2
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• pp.168-172
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• 1999

We have studied the formation of Co/Ti bilayer silicide with low resistivity and good thermal stability on the heavily boron doped $\textrm{p}^{+}$-Si region. In this paper, Co/Ti bilayer silicides were fabricated by depositing Co($150\AA$)/Ti($50\AA$) films on the clean $\textrm{p}^{+}$-Si substrates in an E-beam evaporator and performing the two step RTA process (first annealing: 650$50^{\circ}C$/20sec, second annealing: $800^{\circ}C$/20sec) in a $N_2$ambient with the pressure of $\textrm{10}^{-1}$atm. Co/Ti bilayer silicides obtained from our experiments exhibited the low resistivity of about $18\mu\Omega$-cm and the uniform thickness of about $500\AA$ without change of sheet resistance and agglomeration under the long post0annealing time up to $1000^{\circ}C$.

• Korean Journal of Materials Research
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• v.8 no.7
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• pp.579-583
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• 1998

Silicide layer structures, agglomeration of silicide layers, and dopant redistributions for the Co/Ti bilayer sputter-deposited on the P-doped polycrystalline Si substrate and subjected to rapid thermal annealing were investigated and compared with those on the single Si substrate. The $CoSi_2$ phase transition temperature is higher and agglomeration of the silicide layer occurs more severely for the Co/Ti bilayer on the doped polycrystalline Si substrate than on the single Si substrate. Also, dopant loss by outdiffusion is much more significant on the doped polycrystalline Si substrate than on the single Si substrate. All of these differences are attributed to the grain boundary diffusion and heavier doping concentration in the polycrystalline Si. The layer structure after silicidation annealing of Co/ Tildoped - polycrystalline Si is polycrystalline CoSi,/polycrystalline Si, while that of Co/TiI( 100) Si is Co- Ti- Si/epi- CoSi,/(lOO) Si.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.11
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• pp.908-913
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• 2000

CoSi$_2$/p+/n diodes(bilayer diodes) were fabricated by using epitaxial CoSi$_2$grown from Co/Ti bilayer as a diffusion source. The I-V characteristics of p+/n diodes were measured and compared with those of diode made from Co monolayer (monolayer diode). Monolayer diodes showed typical p+n junction characteristics with the leakage current of as low as 10$^{-12}$ A and forward current 6-orders higher than the leakage current, when drive-in annealed at 90$0^{\circ}C$ for 20 sec.. On the other hand, bilayer diodes showed the Schottky-like behaviors with forward currents rather higher than those of monolyer diodes, but with too high leakage currents, when drive-in annealed at $700^{\circ}C$ or higher. However, when the annealing temperature was lowered to $700^{\circ}C$ and annealing time was increased to 60 sec., the leakage current was reduced to 10$^{-11}$ A and thus sho3wed typical diode characteristics. The high leakage currents for diodes annealed at $700^{\circ}C$ or higher was attributed to Shannon contacts formed due to unremoved Co-Ti-Si precipitates. But when annealed at 50$0^{\circ}C$, B ions diffused in the direction of the surface layer, and thus the leakage currents were reduced by removing Shannon contacts.

• Korean Journal of Materials Research
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• v.13 no.2
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• pp.88-93
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• 2003

Co/Ti bilayer structure in Co salicide process helps to the improvement of device speed by lowering contact resistance due to the epitaxial growth of $CoSi_2$layers. We investigated the epitaxial growth and interfacial mass transport of $CoSi_2$layers formed from $150 \AA$-Co/Ti structure with two step rapid thermal annealing (RTA). The thicknesses of Ti layers were varied from 20 $\AA$ to 100 $\AA$. After we confirmed the appropriate deposition of Ti film even below $100\AA$-thick, we investigated the cross sectional microstructure, surface roughness, eptiaxial growth, and mass transportation of$ CoSi_2$films formed from various Ti thickness with a cross sectional transmission electron microscopy XTEM), scanning probe microscopy (SPM), X-ray diffractometery (XRD), and Auger electron depth profiling, respectively. We found that all Ti interlayer led to$ CoSi_2$epitaxial growth, while $20 \AA$-thick Ti caused imperfect epitaxy. Ti interlayer also caused Co-Ti-Si compounds on top of $CoSi_2$, which were very hard to remove selectively. Our result implied that we need to employ appropriate Ti thickness to enhance the epitaxial growth as well as to lessen Co-Ti-Si compound formation.

• Proceedings of the Materials Research Society of Korea Conference
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• 1995.11a
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• pp.7-7
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• 1995

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.05a
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• pp.57-57
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• 1996

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.5
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• pp.87-92
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• 1998

Ultr shallow p$^{+}$-n junction with Co/Ti bilayer silicidde contact was formed by ion implantation of BF$_{2}$ [energy : (30, 50)keV, dose:($5{\times}10^{14}$, $5{\times}10^{15}$/$\textrm{cm}^2$] onto the n-well Si(100) region and by RTA-silicidation and post annealing of the evaporated Co(120.angs., 170.angs.)/Ti(40~50.angs.) double layer. The sheet resistance of the silicided p$^{+}$ region of the p$^{+}$-n junction formed by BF2 implantation with energy of 30keV and dose of $5{\times}10^{15}$/$\textrm{cm}^2$ and Co/Ti thickness of $120{\AA}$/(40~$50{\AA}$) was about $8{\Omega}$/${\box}$. The junction depth including silicide thickness of about $500{\AA}$ was 0.14${\mu}$. The fabricated p$^{+}$ -n ultra shallow junction depth including silicide thickness of about $500{\AA}$ was 0.14${\mu}$. The fabricated p$^{+}$-n ultra shallow junction with Co/Ti bilayer silicide contact did not show any agglomeration or variation of sheet resistance value after post annealing at $850^{\circ}C$ for 30 minutes. The boron concentration at the epitaxial CoSi$_{2}$/Si interface of the fabricated junction was about 6*10$6{\times}10^{19}$ / $\textrm{cm}^2$./TEX>.