Titanium Tetrakis Isopropoxide Research Articles

Growth behavior and structural characteristics of TiO2thin films using (CpN)Ti(NMe2)2and oxygen remote plasma

This study examined the effect of a novel precursor on the growth behavior and structure of titanium dioxide (TiO2) thin films. TiO2 thin films were deposited by remote plasma atomic layer deposition (RPALD). Dimethylamin-cyclopentadienyl titanium, (CpN)Ti(NMe2)2, was used as a Ti precursor and oxygen plasma was used as a reactant. (CpN)Ti(NMe2)2 is a newly synthesized precursor for TiO2 deposition. Characteristics of TiO2 thin films deposited by (CpN)Ti(NMe2)2 were compared with those of films deposited using a titanium tetrakis isopropoxide (TTIP) precursor. A wide processing window from 170 to 400 °C was observed, and the growth rate was around 0.44 Å/cycle at 200 °C. X-ray photoelectron spectroscopy (XPS) measurements revealed that nearly stoichiometric TiO2 films were deposited. The residual impurity concentrations inside the films were almost the same for (CpN)Ti(NMe2)2 and TTIP. TiO2 films deposited on ruthenium showed a pure rutile phase at a low deposition temperature and low power pre-treatment. Therefore, this TiO2 film is very promising for metal–insulator–metal (MIM) capacitor dielectrics for dynamic random access memory (DRAM) applications.

TiO2/GeOxNy stacked gate dielectrics for Ge-MOSFETs

In this work, we present the results of physical and electrical characterization of Ti-based high-k gate dielectrics on Ge substrates. Titanium tetrakis iso- propoxide (TTIP) was used as the organometallic source for the deposition of ultra-thin TiO2 films on p-Ge (1 0 0) at low temperature (<200 °C) by plasma enhanced chemical vapor deposition (PECVD) technique in a microwave (700 W, 2.45 GHz) plasma cavity discharge system at a pressure of ∼65 Pa. The presence of an ultra-thin lossy GeO2 interfacial layer between the deposited high-k film and the substrate, results in frequency-dependent capacitance–voltage (C–V) characteristics in strong accumulation and a high interface state density (∼1013 cm−2 eV−1). To improve the electrical properties, nitrogen engineering has been employed to convert the lossy GeO2 interfacial layer to its oxynitride, thus forming TiO2/GeOxNy/Ge stacked-gate structure with improved interface/electrical properties. Different N sources, such as NO, NH3 and NO/NH3, have been used for nitrogen engineering. XPS and Raman spectroscopy analyses have been used for surface morphological study. Electrical properties, such as gate leakage current density, interface state density, charge trapping, flatband voltage shift, etc, have been studied in detail for TiO2/GeOxNy/Ge MIS capacitors using the current–voltage (I–V), capacitance–voltage (C–V), conductance–voltage (G–V) and stress (both constant voltage and current) measurements. Although a significant improvement in electrical characteristics has been observed after nitridation in general, the formation of the interfacial GeOxNy layer, obtained from NO-plasma nitridation, is found to provide the maximum improvement among all the nitridation techniques used in this study. It is shown that the insertion of an ultra-thin oxynitride (GeOxNy) interfacial layer is advantageous for producing gate-quality TiO2 high-k dielectric stacks on Ge substrates.

Analysis of interface states of Al/TiO2/Si0.3Ge0.7 MIS structures using the conductance technique

TiO2 films have been deposited at a low temperature (∼150 °C) using titanium tetrakis isopropoxide (TTIP) as an organometallic precursor on Si0.3Ge0.7 heterolayers by a microwave plasma-enhanced chemical vapour deposition system. Interfacial properties of the as-deposited films have been characterized using capacitance–voltage and conductance–voltage techniques measured at different frequencies. The energy distribution of interface states and the relaxation time have been determined from Gp/ω versus ω analysis. A Dit level of Al/TiO2/SiGe MIS capacitors in the range of 2.87 × 1011 eV−1 cm−2 (in EC-0.446) eV to 5.04 × 1011 eV−1 cm−2 (in EC-0.696) eV has been observed from conductance measurements.

Electrical properties of ultrathin TiO 2 films on Si 1− yC y heterolayers

Titanium dioxide (TiO 2) based gate insulators are being considered seriously for next generation metal oxide semiconductor field effect transistor applications due to its high permittivity. In this work, ultrathin TiO 2 films have been deposited at 150 °C on carbon implanted solid phase epitaxy grown strained Si 1− y C y layers by microwave plasma enhanced chemical vapor deposition using titanium tetrakis isopropoxide and oxygen. The deposited films have been analyzed by X-ray photoelectron spectroscopy for chemical composition. Using a metal–insulator–semiconductor capacitor structure, the interfacial and electrical properties of the deposited films have been characterized in the temperature range 25–125 °C. The leakage current has been found to be dominated by the Schottky emission at a low electric field, whereas Poole–Frenkel emission takes over at higher fields.

Electrical properties of TiO2 films deposited on strained Si1−yCy layers

Insulating high dielectric constant (high-k) titanium dioxide (TiO2) films have been deposited on solid phase epitaxially-grown tensilely strained Si1−yCy layers by microwave plasma enhanced chemical vapour deposition using titanium tetrakis isopropoxide (TTIP) as source material and oxygen. Using metal insulator semiconductor capacitor structure, the interface and electrical properties have been studied both at room and high temperature. Good electrical properties are observed in deposited TiO2 thin films.

Interface control in the chemical vapor deposition of titanium dioxide on silicon(100)

A novel deposition sequence has been developed for the growth of carbon-free, amorphous titanium dioxide thin films on p-type Si(100) using titanium tetrakis–isopropoxide (TTIP) as the metalorganic precursor. The deposition process occurs in an ultra-high vacuum chamber and consists of three stages. Initially, a continuous layer of titanium was deposited on silicon at a substrate temperature of 650 K using a Ti sublimator. The substrate temperature was then lowered to 300 K and the titanium layer was oxidized using a gas phase oxygen source to form a TiO x buffer layer. Subsequently, a TiO 2 thin film was deposited by MOCVD using TTIP at low temperature (below 650 K). Auger electron spectroscopy (AES) performed at each stage of growth showed no detectable carbon contamination. Additional AES measurements suggest that at the process temperature, titanium grows on silicon according to the Stranski–Krastanov mode, which permits the uniform growth of the titanium layer. Finally, X-ray diffraction (XRD) studies show that the thermal decomposition of TTIP produces amorphous TiO 2 at 650 K. This unique process allows for the production of a high-quality amorphous titanium dioxide thin film without interfacial carbon contamination.

Determination of effects of deposition and anneal properties for tetranitratotitanium deposited TiO2 dielectrics

Carbon and hydrogen free tetranitratotitanium was synthesized, which is believed to thermally decomposed primarily as: Ti(NO3)4→TiO2+4NO2+O2. The by-products of the thermal decomposition of tetranitratotitanium, which include NO2 and O2, may possibly provide a robust ultrathin tunnel interfacial layer. Due to the hydrogen free nature of thermolysis, N2O may form an oxynitride layer which has been shown to produce thermal oxynitrides with higher quality than NH3-based nitride oxides. Unlike titanium tetrakis isopropoxide (TTIP) deposited films, the interface state density more closely follows the “U” shape characteristic of conventional thermal SiO2/Si interfaces. The integrated interface state density is considerably less for the film annealed at higher temperature, which should produce considerably higher inversion layer mobilities. This improvement of the interface, compared to TTIP deposited films, is believed to be due to the elimination of water vapor from the deposition ambient.

Charge trapping and degradation in high-permittivity TiO2 dielectric films

Suitable replacement materials for ultrathin SiO/sub 2/ in deeply scaled MOSFETs such as lattice polarizable films, which have much higher permittivities than SiO/sub 2/, have bandgaps of only 3.0 to 4.0 eV. Due to these small bandgaps, the reliability of these films as a gate insulator is a serious concern. Ramped voltage, time dependent dielectric breakdown (TDDB), and capacitance-voltage (C-V) measurements were done on 190 /spl Aring/ layers of TiO/sub 2/ which were deposited through the metal-organic chemical vapor deposition (MOCVD) of titanium tetrakis-isopropoxide. Measurements of the high- and low-frequency capacitance indicate that virtually no interface states are created during constant current injection stress. The increase in leakage current upon electrical stress may be due to the creation of uncharged, near interface states in the TiO/sub 2/ film near the SiO/sub 2/ interfacial layer that give rise to increased tunneling leakage.

MOSFET transistors fabricated with high permitivity TiO/sub 2/ dielectrics

Layers of polycrystalline anatase TiO/sub 2/ have been deposited through the thermal decomposition of titanium tetrakisisopropoxide (TTIP). 500 /spl Aring/ films deposited and annealed in oxygen at 750/spl deg/C had average roughnesses (R/sub a/) of about 30 /spl Aring/. Capacitors made from 190 /spl Aring/ layers of TiO/sub 2/ displayed a voltage dependent accumulation capacitance. This was postulated to be caused by finite width effects in the accumulation layer which we have dubbed the quantum capacitance effect. N-channel transistors made with these films showed near ideal behavior, but mobilities were significantly lower than those of thermal oxide MOSFETs. This mobility reduction was believed to be caused by interface states, which fell below 10/sup 11/ cm/sup -2/ eV/sup -1/ at midgap, but rose sharply on either side, unlike the U shaped behavior in thermal oxide MOSFET's.

Structural and electrical characterization of TiO2 grown from titanium tetrakis-isopropoxide (TTIP) and TTIP/H2O ambients

Thin films of TiO2 have been deposited on silicon wafers from titanium tetrakis-isopropoxide (TTIP) and TTIP/H2O using low pressure metalorganic chemical vapor deposition. The films have been characterized by Rutherford backscattering spectrometry, forward recoil spectrometry, x-ray diffraction, and electrical techniques. Dielectric constants of approximately 30 were measured by high frequency C–V. Metal–oxide–semiconductor capacitors were fabricated using sputtered platinum as the upper electrode material. Films deposited in the presence of water vapor had a much lower quality interface with the silicon substrate. Normal thermionic emission was observed when the gate electrode was positively biased and barrier heights were extracted. Dramatically reduced leakage currents and increased barrier heights were seen after 750 °C anneals in dry oxygen. Using a ramped voltage test, capacitors were found to break down at applied fields of 3.0 MV/cm.

Charge Trapping and Degradation of High Permittivity TiO2 Dielectric Metal-Oxide-Semiconductor Field Effect Transistors

AbstractSuitable replacement materials for ultrathin SiO2 in deeply scaled MOSFETs such as lattice polarizable films, which have much higher permittivities than SiO2, have bandgaps of only 3.0 to 4.0 eV. Due to these small bandgaps, the reliability of these films as a gate insulator is a serious concern. Ramped voltage, time dependent dielectric breakdown, and capacitance-voltage measurements were done on 190Å layers of TiO2 which were deposited through the metal-organic chemical vapor deposition of titanium tetrakis-isopropoxide. Measurements of the high and low frequency capacitance indicate that virtually no interface states are created during constant current injection stress. The increase in leakage upon electrical stress suggests that uncharged, near-interface states may be created in the TiO2 film near the SiO2 interfacial layer that allow a tunneling current component at low bias.