Fully Silicided Ni[sub 1−x]Pt[sub x]Si Metal Gate Electrode for p-MOSFETs

Abstract

We investigated Ni 1−x Pt x Si ͑x = 0.05-0.33͒ as a metal gate electrode for p-metal oxide semiconductor field effect transistors ͑MOSFETs͒. Our results showed that, with a proper atomic composition of Ni 1−x Pt x Si, the work function of the gate electrode can be tuned from ϳ4.59 eV ͑for NiSi͒ to ϳ5.21 eV ͑for Ni 0.67 Pt 0.33 Si͒. Negligible variations in both the extracted flatband voltages and gate oxide thicknesses with processing temperature ͑up to 900°C͒ demonstrated the excellent thermal stability of the Ni 0.67 Pt 0.33 Si-SiO 2 gate stacks. High-resolution transmission electron microscopy also showed no evidence of degradation at the Ni 0.67 Pt 0.33 Si-SiO 2 interface and the formation Ni and/or Pt precipitates at/or beneath the SiO 2 -Si interface.The introduction of metal gate electrodes in nanoscale complementary metal-oxide-semiconductor ͑CMOS͒ devices is imperative to overcome problems associated with poly-Si gate such as polydepletion effects and boron penetration. 1 However, to achieve optimal operation of high performance bulk CMOS devices, the required gate work functions for n-and p-channel transistors should be within 0.2 eV of the conduction and valence bandedges of Si, respectively. 2 While tailoring the work functions of poly-Si is achieved readily by dopant incorporation, this may not be true for a metal gate electrode; hence the achievement of appropriate metal gate work functions for nanoscale CMOS devices is crucial to realizing dual metal gate CMOS devices. Recently, fully silicided NiSi was shown to be an attractive alternative to elemental metals for metal gate electrode applications. [3][4][5][6][7][8] It was demonstrated that fully silicided NiSi gates effectively reduce poly-depletion effects and have lower sheet resistance with a work function that can be tuned by the implantation of different dopants ͑e.g., As, P, B, and BF 2 ͒ at varying implant doses into a silicon film before full silicidation. Cabral and co-workers have also recently shown that the work function of the fully silicided NiSi gate can be tuned by the full silicidation of poly-Si or Al-doped poly-Si by a Ni͑Pt͒ alloy, increasing the work function value of the fully silicided NiSi gate to 4.76 and 4.96 eV, respectively. 9 In this letter, we investigated the dependence of Ni͑Pt͒Si gate work function on the Pt content and demonstrated that a continuous and tunable work function from ϳ4.59 to ϳ5.21 eV could be achieved. The effects of Pt incorporation on the Ni͑Pt͒Si-SiO 2 and SiO 2 -Si interface integrity were also examined, which revealed no evidence of degradation. Negligible variations in the extracted flatband voltages and gate oxide thickness from 400 to 900°C rapid thermal annealing also demonstrate the excellent thermal stability of the Ni 0.67 Pt 0.33 Si-SiO 2 interface.Ni 1−x Pt x Si-gated MOS capacitors with different Pt content ͑x = 0.05, 0.10, 0.25, and 0.33, calibrated by Rutherford backscattering for x = 0.05 and 0.10 with x = 0.25 and 0.33 estimated by the ratios of the original Ni and Pt layer thickn...

Effectiveness of Aluminum Incorporation in Nickel Silicide and Nickel Germanide Metal Gates for Work Function Reduction

“…Recently, Ni-alloys have been used during silicidation to modulate the NiSi gate È m and ternary nickel-platinum silicide (Ni 1Àx Pt x Si) was reported to successfully obtain PMOS È m tunability. [6][7][8] Alternatively, gate silicidation using nickel-rare-earth metal alloy (such as Ni-Tb and Ni-Yb) was also investigated for NMOS NiSi gate È m tunablity. 9,10) However, due to the different Ni and rareearth metal silicidation kinetics, the incorporation of low È m rare-earth metals at the gate/dielectric interface for È m modulation is difficult.…”

Full Range Work Function Tuning of MOSFETs using Interfacial Yttrium Layer in fully Germanided Ni Gate

“…Different methods have been reported for tuning the NiSi workfunction to the band edges. These include the use of p-type and n-type dopants in pre-silicided poly-silicon film (5-7), Nialloy (8) and formation of different Ni silicided phases (7) (9). Most of the efforts are focused on changing the gate electrode chemical potential to achieve workfunction tuning.…”

The Effect of an Yttrium Interlayer on a Ni Germanided Metal Gate Workfunction in $\hbox{SiO}_{2}/\hbox{HfO}_{2}$

“…The workfunction value of 4.6-4.7 eV makes NiSi suitable for a midgap (4.61 eV) metal gate application, whereas NiGe appears to be an ideal candidate for p-MOSFETs due to the excellent alignment of its workfunction to the valence band edge (5.17 eV). However, for the application in a dual-metal-gate architecture, the workfunctions of both NiSi and NiGe have to be further [6], Ni alloy [7], and formation of different Ni silicided phases [8], [9]. In our previous study [10], we reported the tuning of the Ni-based FUSI effective workfunction from 4.33 to 3.65 eV via the introduction of an yttrium (Y) layer between the Ni-based FUSI gate electrode and the SiO 2 gate insulator.…”