Search

Atomic layer deposition (ALD) is used in applications where inorganic material layers with uniform thickness down to the nanometer range are required. For such thicknesses, the growth mode, defining how the material is arranged on the surface during the growth, is of critical importance. In this work, the growth mode of the zirconium tetrachloride/water and the trimethyl aluminum/water ALD process on hydrogen-terminated silicon was investigated by combining information on the total amount of material deposited with information on the surface fraction of the material. The total amount of material deposited was measured by Rutherford backscattering, x-ray fluorescence, and inductively coupled plasma–optical emission spectroscopy, and the surface fractions by low-energy ion scattering. Growth mode modeling was made assuming two-dimensional growth or random deposition (RD), with a “shower model” of RD recently developed for ALD. Experimental surface fractions of the ALD-grown zirconium oxide and aluminum oxide films were lower than the surface fractions calculated assuming RD, suggesting the occurrence of island growth. Island growth was confirmed with transmission electron microscopy (TEM) measurements, from which the island size and number of islands per unit surface area could also be estimated. The conclusion of island growth for the aluminum oxide deposition on hydrogen-terminated silicon contradicts earlier observations. In this work, physical aluminum oxide islands were observed in TEM after 15 ALD reaction cycles. Earlier, thicker aluminum oxide layers have been analyzed, where islands have not been observed because they have already coalesced to form a continuous film. The unreactivity of hydrogen-terminated silicon surface towards the ALD reactants, except for reactive defect areas, is proposed as the origin of island growth. Consequently, island growth can be regarded as “undesired surface-selective ALD.” [ABSTRACT FROM AUTHOR]

The downscaling of highk/metal gate transistor devices requires thinfilm deposition processes that deliver not only an outstand ing highk oxide quality, but also a strict interfacial oxide thickness control in the subI nm thickness range. To study the impact of atomic layer deposition (ALD) process conditions and chemistry on the HfO2 quality and interfacial oxide thickness, we have used tetrakis[ethylmethylamino]hafnium (TEMAH) as a metal precursor and H2O and O3 as oxidants. The deposition temperature ranged from 285 up to 365°C, where TEMAH decomposition plays a role in the growth mechanism. Physical characterization and Pt dot capacitor devices have been used to study the impact of the oxidant and process conditions on the equivalent oxide thickness and gate leakage current of 24 nm thin HfO2 films. By combining Xray reflectometry and ellipsometry, we evaluated the Si/highk interfacial oxide layer thickness. Timeofflight secondaryion mass spectroscopy was used to determine the C impurity levels. Both the interfacial oxide layer thickness and the C impurity level in the Si/SiO2/HfO2 stacks are strongly dependent on the oxidant. The temperature dependence of the C impurity level is opposite for O3 and H2O. Furthermore, SiO2 regrowth was found for the O3 process. [ABSTRACT FROM AUTHOR]

We investigate colloidal Fe3O4 nanocrystals as a catalyst system for carbon nanotube (CNT) growth that allows for decoupling the CNT growth step from the catalyst shaping and activation step. The system consists of 6.4 nm Fe3O4 nanocrystals synthesized using a solution-based thermal decomposition reaction and, subsequently, transferred as hexagonally ordered Langmuir–Blodgett (LB) monolayers on TiN substrates. We demonstrate for the first time aligned CNT growth from LB deposited nanocrystals on a metallic underlayer. The hexagonally ordered monolayers of catalyst particles show promising stability up to the CNT growth temperature. In situ TEM heating experiments were performed to find this onset of particle deformation and showed stability of the nanoparticles up to 600 °C. The particle coalescence at high temperatures was also evidenced by the increasing CNT diameter, from 9.5 nm at 580 °C to 16 nm at 630 °C. By choosing to work at temperatures below the onset particle coalescence temperature, equivalent CNT diameters were obtained under different catalyst activation and growth conditions. The high stability of the catalyst on the metallic underlayer enables us to study CNT growth kinetics independently of the catalyst shaping step. This work opens a route towards combining growth studies with an electrical evaluation of the CNT growth as the TiN can be used as the bottom contact. [ABSTRACT FROM AUTHOR]

In this paper, we show the electrochemicaldeposition of a subnanometerfilm of nickel (Ni) on top of titanium nitride (TiN). We exploit theconcept of cluster growth inhibition to enhance the nucleation ofnew nuclei on the TiN substrate. By deliberately using an unbufferedelectrolyte solution, the degree of nucleation is enhanced as growthis inhibited more strongly. This results in a very high particle densityand therefore an ultralow coalescence thickness. To prevent the terminationof Ni deposition that typically occurs in unbuffered solutions, theconcentration of Ni2+in solution was increased. We haveverified with RBS and ICP-MS that the deposition of Ni on the surfacein this case did not terminate. Furthermore, annealing experimentswere used to visualize the closed nature of the Ni film. The closureof the deposited film was also confirmed by TOF-SIMS measurementsand occurs when the film thickness is still in the subnanometer regime.The ultrathin Ni film was found to be an excellent catalyst for carbonnanotube growth on conductive substrates and can also be applied asa seed layer for bulk deposition of a smooth Ni film on TiN. [ABSTRACT FROM AUTHOR]

Abstract: Carbon nanotubes (CNTs) were integrated successfully into 150nm contact holes having a TiN underlayer and a Cu single damascene top contact module. All the integration steps for CNT integration, for patterning the Cu top contact and the mask-set used are compatible with 130nm device technologies on 200mm wafers. The first resistance yield plots for the CNT contacts on full wafer level are presented. For CNT grown at 540°C in contact holes with aspect ratio 1.3, a single CNT contact hole resistance of 3.4kΩ was achieved. The structure designed, the process flow presented here for CNT integration, and the automatic probing constitute a platform that allows benchmarking different recipes and process conditions. This constitutes a significant step forward towards the realization of a contact module with vertical CNT interconnects of superior quality. This is because the platform can speed up the learning cycle time for optimizing the CNT interconnect based on learning from the electrical performance. [Copyright &y& Elsevier]

Abstract: We propose to use carbon nanotube (CNT)–CNT contacts instead of CNT–metal contacts as a route towards low resistance CNT horizontal interconnects. We characterize by electrical transport measurements and Kelvin probe force microscopy the contacts present in CNT horizontal interconnects grown by chemical vapor deposition between titanium nitride electrodes. When two CNTs with diameter around 30nm grow from opposing electrodes and touch each other with their outermost shells, typical contact resistances around 16kΩ are obtained. The corresponding contact resistivity of about 14Ωμm2 is one order of magnitude smaller than the contact resistivity of a CNT touching the TiN surface with its outermost shell. On the other hand, the contact resistance of a CNT grown from a nickel catalyst particle deposited on a TiN electrode is negligibly small when compared to the above mentioned contact resistances. Our results demonstrate that we are able to grow from opposing electrodes CNTs that touch each other with a corresponding high density (up to 1011 cm−2) of CNT–CNT contacts. This may offer an effective solution towards the growth of low resistance CNT horizontal interconnects. [Copyright &y& Elsevier]