Effects of Ti Incorporation in Ni on Silicidation Reaction and Structural/Electrical Properties of NiSi

Abstract

The effects of Ti incorporation in a Ni film on the silicidation reaction as well as the structural and electrical properties of NiSi have been investigated. Experimental results from this work showed that the reaction-inhibiting effect of an interfacial oxide layer could be effectively overcome by Ti incorporation. It was found that, in the presence of a thin interfacial oxide ͑1-2 nm͒, the onset of the silicidation reaction occurs at 300°C with a Ni͑5 atom % Ti͒ alloy while the thin interfacial oxide effectively delays the silicidation reaction up to 700°C for pure Ni. It was found that Ti reacts with the interfacial oxide, yielding an altered oxide layer, which acts as a Ni-permeable diffusion membrane during silicidation. In addition to the dramatic effect on the interfacial reaction during silicide formation, Ti incorporation was also found to improve morphological and thermal stability of NiSi. As a result, Ni͑Ti͒-silicided p ϩ /n diodes ͑with/without an interfacial oxide͒ showed an improvement in junction integrity, as compared to pure Ni-silicided p ϩ /n diodes. It is believed that the ability to form silicide effectively even in the presence of an interfacial oxide, coupled with improved junction integrity, will greatly relieve constraints on processing conditions and significantly enhance manufacturing yield.The use of metallic silicides to reduce the gate and source/drain contact resistance is crucial in achieving high-speed device operation in advanced complementary metal oxide semiconductor ͑CMOS͒ devices. Recently, NiSi has been shown to be an attractive alternative to currently used silicides, i.e., TiSi 2 and CoSi 2 , for future 0.1 and sub-0.1 m generation CMOS devices due to its high conductivity, large processing window, low Si consumption, and ability to maintain low resistivity even for linewidths down to 0.1 m. 1-4 However, a number of process/integration issues, such as the sensitivity of NiSi formation to oxygen impurities ͑e.g., residual oxide on Si surface͒, 5 remain to be addressed and resolved before the full implementation of NiSi process in future sub-0.1 m generations of CMOS devices is realized.It is known that, like CoSi 2 , 6-9 the formation of NiSi is substantially suppressed or even completely inhibited if a thin interfacial oxide is present. 9 For example, it was reported that the presence of a thin native oxide effectively delays the formation of Ni-silicide up to 800°C. 10 This sensitivity of NiSi formation to the interfacial oxide often results in the formation of a rough silicide/Si interface, when the initial Si surface is partially oxidized, or even a complete failure to form NiSi if the initial Si surface is fully oxidized. While the failure to form NiSi would directly result in unacceptably high contact resistance on source/drain and gate regions, the formation of rough silicide/Si interface has been identified as the primary cause for anomalously large junction leakage on shallow junctions. 11 In addition, it has also been shown that NiSi is extremely sensitive to oxy...

Improvement of Thermal Stability of Nickel Silicide Using Co-sputtering of Ni and Ti for Nano-Scale CMOS Technology

“…This conclusion was similarly reported by R.T.P. Lee et al using Ni and Ti alloy targets [11]. Also as our results showed, the sheet resistance was larger with the samples having a larger proportion of Ti in the Ni layer.…”

“…R.T.P. Lee et al considered that this was due to the increase of the thickness of the Ti-related layer with increasing proportion of Ti [11]. And D. Deduytsche et al reported that a small amount of refractory can dissolve into the NiSi lattice or can be present at the grain boundaries, decreasing the NiSi grain size, and presented this result as another possible reason for the increase of sheet resistance [9].…”

NiSi2 formation through annealing of nickel and dysprosium stack on Si(100) and impact on effective Schottky barrier height

“…This phenomenon is similar to the formation of NiSi 2 by annealing a Ni(Ti)/oxide/Si film stack at 300 C, where the oxide layer acts as a diffusion barrier. 39 In addition, the thermodynamic driving force (negative DG total ) for the nucleation of NiSi 2 on Si at a low temperature can be provided by the following factors: (1) the low interfacial energies 39,40 DG i at the NiSi 2 /Si(100) and NiSi 2 /Si(111) interfaces as compared to that of NiSi/Si(100) interface, (2) the small lattice mismatch (0.4%) between NiSi 2 and Si, 39,41 and (3) the small volume change 42 of only 2% arising from the difference in thickness between NiSi 2 and Si (volume change for the difference in thickness between NiSi and Si is 10%). Furthermore, due to the fact that (111) planes of NiSi 2 are parallel to Si (111) and the nucleation of NiSi 2 is easiest on (111) Si planes, the NiSi 2 crystallites therefore take the form of a pyramidal shape.…”

Nickel silicide formation using multiple-pulsed laser annealing

“…2 However, formation of Ni silicide has been found to be very sensitive to the presence of native oxide at the Ni/ Si interface. 3 Ti capping, 4 Ti interlayer, 5 or Ti alloying 6 has been reported to successfully tackle the problem of residual interfacial oxide. After metal deposition, silicide formation is usually carried out by subjecting the whole device wafer to an elevated temperature for a short duration using rapid thermal annealing ͑RTA͒ process.…”