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With ALD-Co on n+ -Ge (ND of $2\times {10}^{{19}}\text {cm}^{\text {-3}}$ ) as the platform, annealing schemes including rapid thermal annealing (RTA) and laser thermal annealing (LTA) were employed to study its impact on the characteristics of CoGe2. CoGe2 formed by LTA shows no agglomeration and a low $\rho _{\text {c}}$ of $1.3\times {10}^{\text {-8}} \Omega $ -cm2 which is reduced by 54 % as compared to the counterpart RTA. In addition, a uniform and atomically smooth CoGe2 with nearly epitaxial crystal structure is also achieved by LTA. Furthermore, LTA-formed CoGe2 does not require any barrier layer during formation which is in stark difference to other germanides and would greatly improve line resistance of the ever scaled contact trench. The promising results mainly stem from the low thermal budget with significant thermal gradient/shallow heat distribution of LTA that effectively limits excess surface Co diffusion and grooving effect, proving the high contact performance enabler beyond 5 nm node.

This letter represents the first direct experimental demonstrations and mechanism proposal regarding abnormal palladium diffusion into germanium (Ge). Our experiments indicated that excess Ge atoms among palladium germanide alloy formation indirectly induce the abnormal out-diffusion of mass palladium atoms into Ge. Consequently, palladium germanide alloy on both n-type and p-type Ge form ohmic-like Schottky junctions. To identify this phenomenon, first-principle calculations and technology computer-aided design simulation were used to evaluate the electrical influence of palladium atoms in Ge. We discovered that the activated palladium atoms in Ge induce large midgap bulk-trap states, which contribute to a severe increment of trap-assisted tunneling current at the palladium germanide/Ge junction.

The process to form Ti germanide on P-implanted Ge ( $ {2} \times {10}^{ {19}}$ cm−3) with low contact resistivity ( $\rho _{c}$ ) was developed. Sequential deposition of Ti and TiN on n-Ge without annealing leads to rectifying ${I}$ – ${V}$ characteristic due to Fermi level pinning. With 600 °C annealing, Ohmic-like ${I}$ – ${V}$ behavior was achieved due to Ti germanide (C54 phase included) formation that depins Fermi level and makes $\rho _{c}$ of ${1.5}\times {10}^{{{-{5}}}} ~\Omega -\text {cm}^{{{2}}}$ and Schottky barrier height for electron ( $\Phi _{\text {BN}}$ ) of 0.22 eV. Even for 700 °C annealing, the Ti germanide exhibits comparable $\rho _{c}$ and good thermal stability without agglomeration, which is a concern of NiGe. By adopting additional P implantation after germanide, $\rho _{c}$ and $\Phi _{\text {BN}}$ can be further improved to ${3.6}\times {10}^{{{- {6}}}}~\Omega $ -cm2 and 0.17 eV, respectively. The improvement is ascribed to the enhanced dopant segregation at the germanide/Ge interface that results in stronger dipoles and more significantly reduced $\Phi _{\text {BN}}$ and $\rho _{c}$ . The Ti germanide process paves a promising path to enable a next-generation Ge technology.

Nickel germanide (NiGe) was formed from atomic layer deposition (ALD) Ni on Ge and a subequent annealing process; the Ni film with low resistivity ( $34~\mu \Omega \cdot \text {cm}$ ) at 15 nm was obtained by N2 + H2 plasma treatment after Ni precursor injection. The formed NiGe film showed low specific contact resistivity ( $\rho _{c})$ values of 9.01 $\mu \Omega \cdot \text {cm}^{2}$ for an NiGe/n+Ge contact and 3.61 $\mu \Omega \cdot \text {cm}^{2}$ for an NiGe/p+Ge contact. These values were comparable to those obtained using sputtered Ni. In addition, the ALD process-based NiGe showed excellent thermal/electrical stability up to 600 °C.

In this paper, we demonstrated the enhancement of thermal stability of nickel germanide (NiGe) alloy up to 600 °C by using titanium nitride (TiN) metal capping. A high ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ ratio of $2.9 \times 10^{5}$ was achieved by capping TiN metal on Ni for NiGe alloy formation at 600 °C. Detailed analyses were performed for realizing the mechanism for TiN capping on NiGe/Ge, including vertical element diffusion profile observation through depth-profiling X-ray photoelectron spectroscopy (XPS), element diffusion distribution by energy-dispersive X-ray spectroscopy mapping, and direct junction leakage current path detection by conductive atomic force microscopy. The experimental results indicated that TiN capping can reduce the risk of agglomeration and form a graded NiGe/Ge Schottky junction that is beneficial for suppressing the degradation of junction leakage. Subsequently, we compared the electrical performance of TiN/NiGe/n-Ge at various N/Ti ratios of TiNs. Based on the depth-profiling XPS results and electrical performance, TiN with an N/Ti ratio of approximately 1:1 can resist the Ni and Ge diffusion, which facilitates the suppression of the agglomeration process. However, the TiN capping layers with an N/Ti ratio of less than approximately 1:1 (Ti-rich) were not favorable for resisting Ni and Ge diffusion.

© 2016 IEEE. Ti/p-Ge and NiGe/p-Ge contacts are compared on both planar- and fin-based devices. Ti/p-Ge contacts show low contact resistance, while NiGe/p-Ge devices show short circuit problems due to thermally driven Ni diffusion. Considering the thermal budget in the standard backend of line processing for CMOS, Ti is more suitable for p-Ge devices. A low Ti/p-Ge contact resistivity of 1.1 × 10-8 Ω cm2 is achieved by using a multi-pulse laser annealing technique for B activation. ispartof: IEEE Electron Device Letters vol:37 issue:4 pages:482-485 status: published

The phosphorus incorporation by chemical vapor deposition and activation by laser annealing reaches the electron concentration of $\sim 3\times 10^{20}$ cm $^{-3}$ . The pulsed laser not only activates the phosphorus but also produces the biaxial tensile strain of 0.35%. With the nickel germanide contact, the specific contact resistivity reaches as low as $1.5\times 10^{-8}~\Omega $ -cm2 by greatly reducing the tunneling distance. Due to 4% misfit between Ge and Si, there are still misfit dislocations near the Ge/Si interface. The misfit dislocations at the Ge/Si interface lead to the ideality factor of 1.6 for the Ge/Si hetero-junction diode with ON/OFF ratio of $\sim 1\times 10^{5}$ .

Free-standing and single-crystalline Cu3Ge nanowires (NWs) were synthesized by a vapor-phase deposition method on the Cu foil. The NWs are grown along the [010] direction via a vapor–solid mechanism. The localized surface plasmon resonance of individual NWs on a Si substrate is investigated using the dark-field scattering spectroscopy. The resonance peak wavelength for NWs with different diameters is observed, which ranges from 500 to 550 nm. This study proves the existence and provides an insight for understanding the LSPR property of free-standing Cu3Ge NWs.

Thermally robust Ni germanide (NiGe) using the cosputtering of Ni and Pt on Ge-on-Si substrate is proposed for high-performance nanoscale germanium metal-oxide-semiconductor field-effect transistors (Ge MOSFETs). The rapid thermal process temperature window for the stable sheet resistance of the proposed Ni-Pt cosputtered structures was about 50-100°C wider than that of the pure Ni structure, with neither NiGe agglomeration nor local penetration of Ni atoms into the substrate. In addition, the surface and interfacial morphologies of the Ni-Pt cosputtered structure were much smoother and more continuous than those of a pure Ni structure. The improvement in the thermal stability was attributed to the change of the crystal structure due to the suppression of the diffusion of Ni atoms and the uniform distribution of Pt atoms. Therefore, this proposed Ni-Pt cosputtered structure could be promising for high-mobility Ge-on-Si MOSFET applications.

We investigate the impact of metal-interfacial layer-semiconductor source/drain (M-I-S S/D) structure with heavily doped n-type interfacial layer (n+-IL) or with undoped IL on sub-10-nm n-type germanium (Ge) FinFET device performance using 3-D TCAD simulations. Compared to the metal-semiconductor S/D structure, the M-I-S S/D structures provide much lower contact resistivity. Especially, the M-I-S S/D structure with n+-IL provides much lower contact resistivity, resulting in $\sim 5 \times $ lower contact resistivity than $1\times 10^{\mathrm {\mathbf {-8 }}}~\Omega $ - $\mathrm{cm}^{\mathrm {\mathbf {2}}}$ , specified in International Technology Roadmap for Semiconductors. In addition, we found that the M-I-S structure with n+-IL remarkably suppresses the sensitivity of contact resistivity to S/D doping concentration.

In this paper, thermally stable Ni germanide using a Ni-Pt(1%) alloy and TiN capping layer is proposed for high-performance Ge MOSFETs. The proposed Ni-Pt(1%) alloy structure exhibits low-temperature germanidation with a wide temperature window for rapid thermal processing. Moreover, sheet resistance is stable and the germanide interface shows less agglomeration despite high-temperature postgermanidation anneal up to 550 °C for 30 min. In addition, the surface of the Ni-Pt(1%) alloy structure is smoother than that of a pure Ni structure both before and after the postgermanidation anneal. Only the NiGe phase and no other phases such as PtxGey and NixPt1-xGey can be observed in X-ray diffraction results, but X-ray photoelectron spectroscopy shows that PtGe is formed during the postgermanidation anneal. The larger Pt atomic radius is believed to inhibit the diffusion of Ni into the Si substrate, thereby improving the thermal stability of the NiGe. The higher melting point of PtGe is also believed to improve thermal stability. Therefore, this proposed Ni-Pt(1%) alloy could be promising for high-mobility Ge MOSFET applications.

Highly thermally stable Ni germanide technology for high performance germanium metal-oxide-semiconductor field-effect transistors (Ge MOSFETs) is proposed, utilizing Pd incorporation into Ni germanide. The proposed Ni germanide shows not only the improvement of thermal stability but also the reduction of hole barrier height, which can improve the device on-current by reducing the Ni germanide to p+ source/drain contact resistance. The proposed Ni germanide showed a stable sheet resistance of up to 500degC 30-min postgermanidation annealing due to the suppression of agglomeration and oxidation of Ni germanide and the diffusion of Ni and Ge atoms by the incorporated Pd. Therefore, the proposed Ni0.95Pd0.05 alloy could be promising for the high mobility Ge MOSFET applications.

In this letter, we report the demonstration of an effective electron Schottky barrier height (ΦBn) reduction technology for NiGe/n-type Germanium (n-Ge) contacts using ion implantation of selenium (Se) followed by its segregation at NiGe/n-Ge interface. Se was found to segregate at NiGe/n-Ge interface after germanide formation. Nickel monogermanide was formed using a 350°C 30-s anneal. Se segregation gives ΦBn as low as ~0.13 eV.

P+Ge1-xSnx is a promising source and drain (S/D) stressor material for Ge p-MOSFETs, and an S/D material in Ge1-xSnx channel p-MOSFETs. In this paper, we investigate the dopant segregation (DS) effects in the stanogermanidation of p+Ge0.947Sn0.053 (boron-doped). A study comparing the contact resistance RC of nickel stanogermanide [Ni(Ge1-xSnx) or Ni(GeSn)] contact on p+Ge1-xSnx and nickel germanide (NiGe) contact on p+ Ge was performed. A more pronounced DS effect is achieved during the stanogermanidation in comparison with the NiGe/p+Ge control. RC is 44% lower in the Ni(Ge1-x Snx)/p+GeSn structure as compared to the NiGe/p+Ge control. The reduced RC is attributed to a more significant DS effect and the lower bandgap of Ge1-xSnx as compared with Ge.

The thermal stability of a nickel germanide film formed on a tensile-strained Ge epilayer on a silicon substrate with a low-temperature Si0.77Ge0.23 (50-nm)/Ge (50-nm) buffer is investigated. A record temperature of 700°C for the stability of sheet resistance of nickel germanide is reported, which is increased by about 150°C compared to that on bulk Ge and comparable to the temperature for nickel silicide on the Si substrate. The improvement of the thermal stability is demonstrated due to the delay of the agglomeration of the nickel germanide film on Ge-on-Si, which is proposed to be attributed to the increase of the tensile strain in the Ge epilayer during thermal annealing due to the thermal mismatch between Si and Ge.

The material and electrical characteristics of /spl epsiv/-Cu/sub 3/Ge as a contact metal were investigated. The samples were prepared by direct copper deposition on germanium wafers, followed by rapid thermal annealing. The /spl epsiv/-Cu/sub 3/Ge formed at 400 /spl deg/C has a resistivity of 6.8 /spl mu//spl Omega//spl middot/cm, which is lower than typical silicides for silicon CMOS. Cross-sectional transmission electron microscopy showed smooth germanide/germanium interface, with a series of nanovoids aligning close to the top surface. These voids are believed to be the results of Kirkendall effect arising from the different diffusion fluxes of copper and germanium. The specific contact resistivity of Cu/sub 3/Ge, obtained from four-terminal Kelvin structures, was found to be as low as 8/spl times/10/sup -8/ /spl Omega//spl middot/cm/sup 2/ for p-type germanium substrate. This low resistivity makes Cu/sub 3/Ge a promising candidate for future contact materials.

We have measured the physical properties and resistivity of nickel germanide thin films formed by the rapid thermal annealing of nickel metal on p-type germanium substrates. Rutherford back scattering and high-resolution electron diffraction confirm that the stoichiometry of the resulting nickel germanide film corresponds to NiGe and has an orthorhombic unit cell with dimensions comparable to that of bulk samples. Transmission electron microscopy shows a poly-crystalline film structure with grain size > 0.1 /spl mu/m. The resistivity values for films annealed in the range 350/spl deg/C-500/spl deg/C are comparable to those of metal silicides. Measurements of the specific contact resistance suggest that values approaching 2 /spl times/ 10/sup -7/ /spl Omega/.cm/sup 2/ can be realized using NiGe formed on heavily doped p-type germanium.

We demonstrate, for the first time, successful operation of Schottky-barrier source/drain (S/D) germanium-on-insulator (GOI) MOSFETs, where a buried oxide and a silicon substrate are used as a gate dielectric and a bottom gate electrode, respectively. Excellent performance of p-type MOSFETs using Pt germanide S/D is presented in the accumulation mode. The hole mobility enhancement of 50%/spl sim/40% against the universal hole mobility of Si MOSFETs is obtained for the accumulated GOI channel with the SiO/sub 2/-Ge interface.

Schottky-barrier source/drain (S/D) germanium p-channel MOSFETs are demonstrated for the first time with HfAlO gate dielectric, HfN-TaN metal gate and self-aligned NiGe S/D. The drain drivability is improved over the silicon counterpart with PtSi S/D by as much as /spl sim/5 times due to the lower hole Schottky barrier of the NiGe-Ge contact than that of PtSi-Si contact as well as the higher mobility of Ge channel than that of Si.

In this paper, state-of-the-art laser thermal annealing is used to form germanide contacts on n-doped Ge and is systematically compared with results generated by conventional rapid thermal annealing. Surface topography, interface quality, crystal structure, and material stoichiometry are explored for both annealing techniques. For electrical characterization, specific contact resistivity and thermal stability are extracted. It is shown that laser thermal annealing can produce a uniform contact with a remarkably smooth substrate interface with specific contact resistivity two to three orders of magnitude lower than the equivalent rapid thermal annealing case. It is shown that a specific contact resistivity of 2.84 × 10 -7 Ω·cm 2 is achieved for optimized laser thermal anneal energy density conditions.

The dynamic pyromagnetic response of several materials with magnetic phase transitions near 300°K has been measured by a method initially described by Chynoweth [1]. The results indicate that practical broad-band pyromagnetic radiation detectors operating in a fast dynamic thermal mode are possible. The best results were obtained with gadolinium and manganese germanide crystals which have second-order magnetic phase transitions slightly below 300°K. Their responses peaked at 300°K, but remained high over fairly large temperature ranges, a 25°C interval in the case of gadolinium. The NEP of ∼ 10-8W.Hz-1/2(0.12 cm2active area) obtained with gadolinium is larger by a factor of 10 than that reported for 300°K pyroelectric detectors, but was limited by laboratory noise pickup in the detector coil rather than the internal Johnson noise. Improved techniques should result in lower NEPs. The pyromagnetic responses at the critical temperatures of two materials with first-order magnetic phase transitions, FeRh and MnAs, were considerably smaller than expected. They were also anomalously discontinuous compared with the measured step in the static magnetization. A third material, Fe .71 Mn 1.44 As, with a first-order transition at 344°K, gave a much larger response, but over a very narrow temperature range.

Using gadolinium and manganese germanide crystals we have previously demonstrated the feasibility of fast broad-band pyromagnetic detectors utilizing the critical transition of their spontaneous magnetization. In the present study we have carried out a formal thermodynamic analysis of other reversible quasi-static pyromagnetic phenomena in an attempt to discover new detection mechanisms. The formal result was applied to the case of a uniaxial ferromagnet and the results compared with experiments on gadolinium single crystals. The pyromagnetic response associated with a transition of the hard axis component of the magnetization is in good qualitative agreement with the theory. We also predict a significant increase in the response of the easy axis component with a field applied along the hard axis, but this has not yet been observed. We have made initial measurements of the pyromagnetic response at the Meissner transition of superconducting lead and tantalum. Their pyromagnetic response peaks near the critical point and has a field dependence consistent with their demagnetizing factors. The latter are at present limiting the responsivities to a few volts/watt.