Tetrakis Diethylamino Titanium Research Articles

Atomic Layer Deposition of Environmentally Benign Tin-Titanate for Ferroelectric Application

Perovskite-based oxides that possess ferroelectric properties, such as BaTiO3 and PbTiO3, have long been a research interest because of their wide applications in devices such as actuators and sensors.1 Due to the toxicity of lead, emphasis has been put on the replacement of Pb2+ by isoelectronic, environment friendly Sn2+, in hope of maintaining similar ferroelectric performance.Theoretical studies using first principle calculations have predicted that perovskite SnTiO3 (P-SNO) would exhibit excellent ferroelectric properties,2-6 yet the actual synthesis of P-SNO by conventional methods remains unsuccessful due to the less stable Sn2+ at high temperatures.2,3 No success was achieved in depositing P-SNO thin films, either. Several studies suggest that P-SNO is metastable,2,7,8 which leads to the proposition of alternative synthetic routes that can stabilize the metastable structure,9 such as atomic layer deposition (ALD)3/chemical vapor deposition (CVD), sol-gel, etc.2 Different from the predicted perovskite structure, nonpolar, ilmentile-type thin film of SnTiO3 has been achieved on sapphire and perovskite substrates using pulsed laser deposition (PLD) techniques from ceramic SnO2 and TiO2 targets.10 This result further motivates a more thorough investigation as to whether or not thin film deposition techniques could stabilize the metastable P-SNO structure which is crucial for high ferroelectric performance.In this work, we report the result of atomic layer deposition of tin-titanate using tin(II)acetylacetonate (Sn(acac)2) and tetrakis(diethylamino)titanium (TDEAT). The ALD reaction is carried out on Si substrates using a custom-built ALD reactor (Fig. 1).11 ALD process parameters were optimized for SnOx and TiO2 deposition. Linear growth behavior was observed for both the films, indicating self-limited ALD growth. The ALD temperature windows of both ALD processes were found to overlap, which facilitates co-deposition of SnOx and TiO2 for tin-titanate deposition. The resulting film is subsequently analyzed by several characterization techniques to determine its stoichiometry, composition, impurities and structural and surface characteristics. The results of this work provide more insights into achieving lead-free, perovskite SnTiO3 structure to facilitate future research on this subject.

Novel functionalization of Ti-V alloy and Ti-II using atomic layer deposition for improved surface wettability

Surface wettability characteristics of commercially pure titanium (CP-Ti/Ti-II) and titanium Grade 5 alloy (Ti–6Al–4V/Ti-V) with 10nm-thick atomic layer deposited (ALD) TiO2 from Tetrakis DiEthyl Amino Titanium and water vapor were studied in conjunction with cleaning steps before and after the ALD treatment. The wettability characteristics of rough Ti-II and Ti-V samples were investigated after each step, that is, as received, after de-ionized (DI) water rinse followed by N2 drying, sonication in methanol, ALD treatment, and post-ALD DI water rinse. Samples without ALD or cleaning treatments were hydrophobic to variable extents, depending on exposure to different environments, surface impurities, roughness, and aging. Surface treatments reported in the literature resulted in hydrophilic/hydrophobic surfaces likely due to organic and/or inorganic impurities. In this study, (i) it is established that it is critically important to probe surface wettability after each substrate treatment; (ii) both Ti-II and Ti-V surfaces are found to become more hydrophilic after each one of the sequential treatments used; and (iii) independently of the initial wettability characteristics of Ti-II and Ti-V surfaces, the aforementioned treatments result in a water contact angle well below 10°, which is an important factor in cellular response. X-ray photoelectron spectroscopy of ALD titania films indicated trace impurities in them. Grazing incidence X-ray diffraction suggested amorphous ALD TiO2 at 200°C; anatase TiO2 was obtained with as little as 5min annealing at 600°C in nitrogen.

Atomic Layer Deposition of HfO2, TiO2, and HfxTi1 − xO2 Using Metal (Diethylamino) Precursors and H2O

Tetrakis (diethylamino) hafnium (TDEAH), tetrakis (diethylamino) titanium (TDEAT), and were used for the atomic layer deposition (ALD) of , , and films on silicon substrates. The ALD temperature windows were found to be for and for . The overlap region is ideal for the ALD of the films. Different compositions of were obtained by varying the cycle ratios, and excellent tunability of film composition was found using X-ray photoelectron spectroscopy (XPS). The deposition rate was found to be the superposition of the two individual growth rates. Both as-deposited and postdeposition annealed films were studied with XPS, phase shift interferometry, and grazing incidence X-ray diffraction. As-deposited and films were found to be amorphous, and they began to crystallize after annealing at in the monoclinic phase and in weak anatase phase . The films remained amorphous after annealing up to about in for .

Band Gap Narrowing versus Formation of Electronic States in the Gap in N−TiO2 Thin Films

N-containing TiO2 thin films with different amounts of nitrogen have been prepared by plasma enhanced chemical vapor deposition (PECVD) by using different titanium precursors without (titanium isopropoxide, TTIP) and with (tetrakis diethylamino titanium, TDEAT and tetrakis dimethylamino titanium, TDMAT) nitrogen in their structures and different N2/O2 ratios as plasma gas. For low/high content of nitrogen, Ti−NO- and/or Ti−N-like species have been detected in the films by X-ray photoelectron spectroscopy (XPS). Their optical behavior is characterized by a red shift of their absorption edge when Ti−N species are a majority, and by an unmodified edge with localized absorption states in the gap when only Ti−NO-like species are present in the film. The experimental results have been interpreted by calculating the density of states of model systems consisting of a 2 × 2 × 3 repetition of the anatase unit cell. This basic structure incorporates nitrogen defects in either substitutional or interstitial lattice p...

Ti Source Precursors for Atomic Layer Deposition of TiO2, STO and BST

In this study we evaluated several precursors such as tetrakis(dimethylamino) titanium (TDMAT), tetrakis (diethylamino) titanium (TDEAT), tetrakis(ethylmethylamino) titanium (TEMAT) along with novel PrimeTiTM, StarTiTM and TyALDTM for TiO2 ALD application with both water and ozone as the oxidizer. Each precursor is evaluated with respect to some of the important characteristics like growth rate of TiO2 per ALD cycle, range and upper limit of process temperature window, volatility and stability of precursor, chemistry with desired oxidizer etc., that are critical for the selection of the precursor. All amino-compounds had a narrow process window. Precursor decomposition was observed for TDMAT, TDEAT and TEMAT at temperature higher than 225 oC limiting the deposition process at 225 {degree sign}C. On the other hand, TiO2 ALD using PrimeTiTM and StarTiTM is observed up to 325 and 400 {degree sign}C respectively. Finally, photoelectron spectroscopy analysis of some the films will be discussed.

Numerical studies on PACVD processes used for TiN multifunctional films using metal organic precursors

In this study, we performed a numerical simulation of the low-temperature thin-film growth of TiN layers in a plasma-assisted MOCVD reaction chamber for the purpose of eventual scale-up. Tetrakis(dimethylamino)titanium (TDMAT) or tetrakis(diethylamino)titanium (TDEAT) is commonly employed as a precursor for TiN layers to avoid chlorine contamination on the substrate. A reaction mechanism of TiN layer formation from TDMAT/TDEAT under the plasma-activated condition suggested by the mass spectrum analysis is employed for numerical calculations. This study is expected to make significant contributions to the understanding of the plasma-activated TiN reaction pathways, which are not yet clearly understood. The deposition rate is dependent on the process parameters such as the flow rate, pressure and plasma power, as well as the concentration gradient near the substrate. In this study, the multiple parameters described above are examined through numerical analysis to determine the deposition rate as well as to provide optimal processing conditions.

Effect of NH3 on the low pressure chemical vapor deposition of TiO2 film at low temperature using tetrakis(diethylamino)titanium and oxygen

The effect of NH3 on TiO2 film deposition using tetrakis(diethylamino)titanium (TDEAT) and O2 as source gases in a low pressure chemical vapor deposition reactor was studied at low temperatures ranging from 100to250°C. TiO2 film is traditionally deposited at temperature above 300°C using oxygen-based Ti precursors, such as titanium tetraisopropoxide. In this study, the authors demonstrate that a combination of both reactive precursors, i.e., TDEAT and NH3, is an effective technique for TiO2 film deposition at lower temperatures, albeit with some nitrogen incorporation. It was found that films can be formed at temperatures as low as 100°C when NH3 is used. At higher temperatures, the growth rate of TiO2 films deposited using NH3 is higher than that of films deposited without NH3 by up to one order of magnitude. X-ray photoelectron spectroscopy data show that NH3 enhances the formation of TiNO and TiN, and x-ray diffraction analysis shows that all as-deposited films have amorphous structure. Both x-ray photoelectron spectroscopy and secondary ion mass spectroscopy depth profiles show that nitrogen, carbon, and oxygen are uniformly distributed throughout the film. The mechanism of enhancement of growth rate using NH3 is also discussed.

Comparison of TiN Films Deposited Using Tetrakisdimethylaminotitanium and Tetrakisdiethylaminotitanium by the Atomic Layer Deposition Method

TiN films were deposited by the atomic layer deposition (ALD) method using either tetrakisdimethylaminotitanium (TDMAT) or tetrakisdiethylaminotitanium (TDEAT) as the Ti precursor and NH3 as the reactant gas. The TiN films deposited using TDMAT showed two saturated TiN film growth regions which were observed in the temperature ranges between 175 and 190°C and between 200 and 210°C. The TiN films deposited using TDEAT showed a saturated growth rate in the temperature range between 275 and 300°C. The growth rates of the TiN films deposited using either TDMAT or TDEAT were about 5 and 1 Å/cycle, respectively. The TiN films grown by the ALD method showed relatively low carbon content compared to the TiN films deposited by other conventional chemical vapor deposition and metalorganic chemical vapor deposition methods using the same precursors. The resistivity of the TiN films deposited by the ALD method was below 1,000 µΩ·cm. The TiN films deposited using TDEAT showed a lower resistivity than the films deposited using TDMAT. The calculated densities of the TiN films deposited using either TDMAT or TDEAT were about 3.55 and 4.38 g/cm3, respectively. This paper presents a comparison of the characteristics of the TiN films deposited using the two different precursors, TDMAT and TDEAT.

Optimisation of the MOCVD of Ti(C, N) in a pulsed H2 - N2 plasma by gas-phase analysis

Favourable gas-phase conditions for the deposition of Ti(C,N) in a large scale reactor vessel have been determined by a mass spectroscopic study of the activation of tetrakis(dimethylamino)titanium (TDMAT) and tetrakis(diethylamino)titanium (TDEAT) in a mixed H 2 -N 2 pulsed DC plasma. Activated hydrogen seemingly attacks the M-L bond. At least part of the ligands are stripped from the Ti atom. This prevents hydrocarbon incorporation in the coating. However, no nitrogen remains available for the formation of TiN. Addition of N 2 to a H 2 plasma seems to result in transamination. Transamination by NH (1≤x≤4) in a H 2 -N plasma appears to be a very attractive mechanism for cleavage of ligands and nitrogen supply at low temperatures. Deposition under preferred conditions produced bronze adherent coatings. The hardness varied between 1600 and 2300 kgf/mm 2 on stainless steel and tungsten carbide. The coatings are very ductile and might improve wear resistance of tools in non-lubricating forging processes.

Low pressure MOCVD of TiN thin films

From multiple regression analysis in the bottom coverage and resistivity of TiN films deposited using tetrakis(diethylamino)titanium (TDEAT), contour maps were calculated as functions of wafer temperature and reactor pressure. High bottom coverage and low resistivity were predicted at low pressure and low temperature with NH 3 additives. Films have been deposited below 400°C and total reactor pressures below 133.3 Pa. Especially by adding a little NH 3 to TDEAT, bottom coverages of 100% have been accomplished in 4.0 aspect ratio contacts with 300 nm diameter. Film resistivities have been also decreased from 24, 000 μΩ cm to about 10, 000 μΩ cm with 15 sccm NH 3.

Comparison of TiN films produced by TDEAT (Ti[N(C2H5)2]4), TDMAT (Ti[N(CH3)2]4), and a new precursor TEMAT (Ti[N(CH3)C2H5]4)

AbstractTiN films have been deposited by chemical vapor deposition (CVD) from a new TiN precursor, tetrakis(ethylmethylamino)titanium (TEMAT), and compared with those from tetrakis(diethylamino)titanium (TDEAT) and tetrakis(dimethylamino)titanium (TDMAT) in terms of film quality and conformality. The TDEAT process at 350°C provides films with low resistivity of ˜2500μΩ-cm and 30% carbon. In addition, films deposited from TDEAT contain no oxygen and show good stability in resistivity with time. Furthermore, this process provides bottom-coverage ranging from 65% at 275°C to 30% at 350°C. In contrast, excellent bottom-coverage of ˜90% over 0.5μΩ contact holes is obtained by the TDMAT process. However, films deposited from TDMAT are air-reactive upon air-exposure, resulting in a large increase in resistivity when exposed to air. The use of TEMAT, possessing physical properties between those of TDMAT and TDEAT, allows less air-reactive and better crystalline films, compared with TiN films from TDMAT. It is also observed that the carbon level is ˜2x lower than that in TiN films from TDEAT. Futhermore, this process provides good step-coverage in 0.35μΩ contacts with an aspect ratio of 2.9. Consequently, the TEMAT process can be an attractive choice for sub-0.5 μΩ application.

Kinetics and conformality of TiN films from TDEAT and ammonia

We propose a heterogeneous reaction mechanism which is consistent with experimental observations of the kinetics of metal-organic chemically vapor deposited TiN films from tetrakisdiethylaminotitanium (TDEAT) and ammonia. The proposed mechanism includes the readsorption of diethylamino radicals, which are formed as a byproduct of the deposition reaction. We use film profiles in holes on patterned wafers, in addition to available growth rate data from flat wafer experiments, to estimate parameter values for a kinetic expression derived from the proposed mechanism. EVOLVE, a low pressure deposition process simulator, is used to estimate the value of the adsorption parameter for the adsorbing reaction byproduct. Reactant partial pressures at the wafer surface are estimated simultaneously. Step coverage depends on both the spatially dependent TDEAT sticking factor and the value of the adsorption parameter for the inhibiting byproduct. The byproduct inhibition model can explain the observed kinetics as well as the film conformality; however, film profiles calculated using a simple sticking factor model (first order reaction model) matched experimental profiles almost as well. In this simple model, the step coverage of TDEAT sourced films depends on the sticking factor of the depositing species, which may be formed by homogeneous reactions. The activation energy estimated using the byproduct inhibition model is about 2300 cal g −1 mol −1.

Low temperature MOCVD of advanced barrier layers for the microelectronics industry

Metalorganic chemical vapor deposition (MOCVD) of TiN thin films at low temperatures and low pressures using tetrakis(diethylamino) titanium (TDEAT) and NH 3 is described. Conformal TiN films, having layer resistivities as low as 200 μΩ·cm, densities close to those of sputtered films, and low impurity contents can be obtained with this chemistry. These TiN films can be applied as adhesion layers for chemical-vapor-deposited W, or as barrier layers between Si and Al. Rapid thermal anneal (RTA) of MOCVD-TiN and physical-vapor-deposited (PVD) Ti/MOCVD-TiN bi-layers is described. RTA at temperatures of 600 to 800°C is shown to lead to formation of a TiSi 2/TiN bi-layer on Si substrates, just as with completely sputter-deposited Ti/TiN bi-layers. Low contact resistance to p +-Si is demonstrated with PVD-Ti/MOCVD-TiN bi-layers. It is demonstrated that thermal decomposition of TDEAT (i.e. without NH 3 as the coreactant) leads to films having better conformality. But, the resistivity and impurity content of the material produced by thermal decomposition of TDEAT is too high for them to be good candidates for barrier and adhesion layers.