Boron redistribution during formation of nickel silicides

Zaring, Carina; Jiang, Han; Svensson, B. G.; Östling, Mikael

doi:10.1016/0169-4332(91)90255-i

Cited by 16 publications

(14 citation statements)

References 19 publications

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“…During the silicidation the Ni forms silicide phases consuming the doped Si. Impurities segregate out of the silicide because of their silicide solubility is low [10]- [12]. However, the diffusivity of the dopants in Si is not significant at the silicide formation temperature (360 C-450 C), so the impurities segregate to the formation boundary between the nickel silicide and the remaining poly-Si.…”

Section: Discussionmentioning

confidence: 97%

Threshold voltage control in NiSi-gated MOSFETs through SIIS

Kedzierski

Boyd

Cabral

et al. 2005

IEEE Trans. Electron Devices

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Complete gate silicidation has recently been demonstrated as an excellent technique for the integration of metal gates into MOSFETs. From the various silicide gate materials NiSi has been shown to be the most scalable. In this paper, a versatile method for controlling the workfunction of an NiSi gate is presented. This method relies on doping the poly-Si with various impurities prior to silicidation. The effect of various impurities including B, P, As, Sb, In, and Al is described. The segregation of the impurities from the poly-Si to the silicide interface during the silicidation step is found to cause the NiSi workfunction shift. The effect of the segregated impurities on gate capacitance, mobility, local workfunction stability, and adhesion is studied.

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Section: Discussionmentioning

confidence: 97%

Threshold voltage control in NiSi-gated MOSFETs through SIIS

Kedzierski

Boyd

Cabral

et al. 2005

IEEE Trans. Electron Devices

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“…3 shows SIMS profiles for the NiSi FUSI with As-and B-doped poly-Si samples before and after FUSI, and with and without a TiN capping layer. Silicidation has been reported to segregate (snow-plow) dopants to the surface and the interface, causing dopant redistribution [13], [14]. In Fig.…”

Section: Resultsmentioning

confidence: 99%

Work Function Tuning of Fully Silicided NiSi Metal Gates Using a TiN Capping Layer

Sim

Wen

et al. 2004

IEEE Electron Device Lett.

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This paper investigates a new way of tuning the work function of fully silicided (FUSI) NiSi metal gates for dual-gate CMOS using a TiN capping layer on Ni to control the poly-Si dopant distribution during FUSI formation. In addition, by comparing the work function change of NiSi FUSI with and without TiN capping, we provide clear evidence that dopants at the gate electrode and dielectric interface are responsible for the work function change. The TiN capping layer causes no degradation to the underlying gate dielectric in terms of fixed-oxide charge, gate leakage current, and time-dependent dielectric breakdown characteristics.

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“…Silicidation has been reported to segregate ͑snow-plow͒ dopants to the surface and the interface, causing dopant redistribution. 14,15 At such high silicidation temperatures ͑800°C͒, dopant out-diffusion is expected to be more severe than that of NiSi ͑500°C͒. The use of a TiN capping layer now acts as a diffusion barrier for As out-diffusion, and thus incorporates more As at the gate/ interface.…”

Section: G120mentioning

confidence: 98%

Investigation of Dopant Effects in CoSi2 and NiSi Fully Silicided Metal Gates

Wen

Liu

Sim

et al. 2005

Electrochemical and Solid-State Letters

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CoSi 2 full silicidation ͑FUSI͒ of doped poly-Si metal gates was investigated to further the understanding of the modulation of effective work function from dopants in CoSi 2 and NiSi FUSI gated metal oxide semiconductor devices. By using a TiN-capping layer to manipulate the dopant distribution, dopants have been confirmed to be effective in tuning the work function for both CoSi 2 and NiSi. However, from the drastic reduction of the As tuning effect in CoSi 2 , we understand that the amount of effective work function tuning is not only directly dependent on the interfacial dopant concentration, but the mechanism of dopant tuning the work function is strongly dependent of the bulk material type.Full silicidation ͑FUSI͒ of doped polysilicon gate has recently been proposed with a process compatible with present complementary metal oxide semiconductor ͑CMOS͒ technology to form tunable work function metal gates. NiSi, TiSi, and HfSi FUSI gates have been shown with tunable effective work function from variation of the type and concentration of dopants in poly-Si. As, B, P, and Sb dopants were found to be capable of setting threshold voltages suitable for n-and p-channel metal oxide semiconductor ͑NMOS and PMOS͒ transistors. 1-10 The mechanism of dopant incorporation on tuning the effective work function has not been thoroughly understood; possibilities of this change include metal/dielectric interface dipole formation, or interfacial grain structure change, etc. To enhance our understanding on this issue, CoSi 2 FUSI gates has been formed in comparison to the commonly researched NiSi FUSI gates with identical dopant incorporation processes. Undoped CoSi 2 FUSI gates also exhibits an effective work function near midgap. 2 Due to agglomeration effects and the reaction kinetics of CoSi 2 , some concerns need to be addressed for integration in the gate-last process when fully siliciding small poly-Si gate dimensions. 10 Other reports have suggested that high-temperature processes cause metal diffusion of Co toward the gate dielectric. 11 However, CoSi 2 is an attractive candidate for the FUSI gate due to its low resistivity and excellent thermal stability which is capable of withstanding the high S/D annealing temperature. In this work, a TiN-capping layer has also been added on the gate material to help identify the relationship between the distribution of As and B dopants and the work function. A distinct difference in the effect of dopant on work function tuning in CoSi 2 compared to that in NiSi has been observed. The role of the TiN-capping layer on dopant distribution on As-doped samples is also different from that observed in B-doped samples, and the trend in NiSi FUSI gates. 12 Explanation of the mechanism for dopant tuning effect is still uncertain; however, this observation suggests that dopants still play a factor in the work function change of CoSi 2 , and the differences in effective work function modulation is highly dependent on the bulk silicide material. ExperimentalCapacitors with 2.5 nm thick gate oxid...

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Boron redistribution during formation of nickel silicides

Cited by 16 publications

References 19 publications

Threshold voltage control in NiSi-gated MOSFETs through SIIS

Threshold voltage control in NiSi-gated MOSFETs through SIIS

Work Function Tuning of Fully Silicided NiSi Metal Gates Using a TiN Capping Layer

Investigation of Dopant Effects in CoSi2 and NiSi Fully Silicided Metal Gates

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