HfO 2 films were grown by atomic layer deposition ͑ALD͒ from Hf͓N͑CH 3 )(C 2 H 5 )] 4 and H 2 O on Si͑100͒ substrates. The thickness of 5-45 nm thick films on HF-etched Si was proportional to the number of growth cycles. Crystallization was observed in the 30-45 nm thick films, containing the monoclinic HfO 2 polymorph. Films with thicknesses lower than 10 nm were amorphous. The effective permittivity of the dielectric films varied between 6.5 and 17. The leakage and capacitive characteristics did not show any clear dependence on the HfO 2 growth temperature. HfO 2 is a recognized candidate for high-permittivity dielectric oxide in complementary metal-oxide-semiconductor ͑CMOS͒ devices. 1 The promise for the suitability of HfO 2 for near-term implementation in CMOS transistors stems from its thermal stability in contact with silicon and from its high bandgap ensuring its insulating properties. Uniform growth of ultrathin and dense dielectric layers on complex-shaped, trenched, and large-area substrates common in microelectronic industry can be provided using atomic layer deposition ͑ALD͒ routes to HfO 2 . [2][3][4][5] In ALD, a substrate surface is alternately exposed to highly reactive metal and oxygen precursors and the solid film forms as a result of successive surface reactions between ͑sub͒monolayers of precursor molecules alternately adsorbed. Since the precursors do not meet in the gas phase, they can be chosen to be as reactive as possible to ensure rapid surface reactions and formation of dense structures at as low temperatures as possible. However, monotonously decreasing growth temperature has usually caused a monotonous increase in the residual contamination when common precursors such as metal halides were used, especially at temperatures below 300°C. 6-8 Increase in impurity levels directly results in lower film density and inferior dielectric properties.In recent ALD studies, the use of hafnium alkylamides has been described. 4,9,10 In the case of hafnium tetrakis͑ethylmethylamide͒, Hf͓N͑CH 3 )(C 2 H 5 )] 4 , and H 2 O, 10 it is reported, that crystalline, 100-200 nm thick HfO 2 films can be grown with high rates and uniform compositions at lower temperatures ͑at 200-300°C͒ than found necessary for halide ALD ͑300°C and higher͒. The oxygen to hafnium ratio was found to be 2.0 Ϯ 0.1, with carbon and nitrogen residues of 0.3-0.6 and 0.1-0.2 atom %, respectively. The hydrogen content was, however, rather high, reaching 2-3 atom %.In the present study, thin HfO 2 films were atomic layer deposited from the liquid hafnium precursor Hf͓N͑CH 3 )(C 2 H 5 )] 4 and H 2 O in order to investigate the growth of ultrathin films with this precursor combination. The influence of the number of growth cycles on film thickness and structure was examined. The effect of substrate temperature on the film growth rate, capacitance-voltage, and leakage current characteristics was monitored. ExperimentalThe films were grown in a hot-wall horizontal flow-type F120 ALD reactor 11 onto Si͑100͒ substrates. The substrate temperat...

This study describes deposition of HfO 2 thin films by chemical vapor deposition ͑CVD͒ and atomic layer deposition ͑ALD͒ using HfI 4 as the metal precursor. The layer-by-layer growth was also studied in real time with a quartz crystal microbalance. In ALD, the deposition rate was independent of the growth temperature, whereas in CVD, an exponential rate increase was observed. Monoclinic HfO 2 was deposited on MgO and poly-Si substrates in a wide temperature range, and the choice of substrate had a strong influence on the orientation of the films. Epitaxial growth of HfO 2 was observed on MgO͑001͒ substrates at 400-500°C in the ALD process and at 500-600°C in the CVD process. The electrical characterization showed that the crystallinity of the films had a stronger influence on the dielectric constant than did the film thickness.

Chemical vapor deposition (CVD) of the superconducting YBa2Cu307 = phase from the halide precursors YX:~, BaX2 and CuX, where X = C1 or I, was thermodynamically investigated. The oxygen source was O2, H20, or a mixture of 02 + HzO. The effect of different deposition parameters on the yield of the YBa2Cu:~OT_ ~ phase was studied and the results are summarized in calculated CVD stability diagrams. The choice of metal halide was found to affect the phase stability of YBa2Cu307 = to a large extent. The best conditions were obtained by using exclusively iodides as metal precursors and with O2 as the oxygen source. For a total pressure of 10 kPa, YBa2Cu~O~_~. can be deposited with 100% yield fi)r all values of the [O2]/([YI3] + [BaI2] + [CuI]) molar ratio between 10 ~ and 10 ~, if the temperature is below 900~ If chlorides are used as metal precursors, the presence of H20 is found to be necessary in order to deposit the superconducting phase.Since the discovery of the new oxide high-Tr superconductors, various techniques have been employed to prepare superconducting films. One of the most attractive methods is chemical vapor deposition (CVD). The CVD technique oilers several advantages; control of the oxygen activity during growth, deposition of extremely dense material, control of microstructure and texture, and in situ growth of superconducting films can be obtained. The most common precursors in CVD of these superconductors are different metal chelates. Such precursors have been used to deposit thin films of the superconducting phases in the Y-Ba-Cu-O system [see e.g., (1-5)], the Bi-Sr-Ca-Cu-O system [see e.g., (6-8)], and the T1-Ba-Ca-Cu-O system (9, 10). A disadvantage with using metal chelates is the risk for carbonate formation in the grain boundaries, which also has been observed (5). Carbonate formation can be prevented by using metal halides as source materials. Only two investigations exist where the superconducting phase has been deposited from the respective metal halides, viz., in the Y-Ba-Cu-O system (11) and in the Bi-Sr-Ca-Cu-O system (12). In both studies a mixture of chlorides and iodides was used, YCI:, + BaI2 * CuC1 for the YBa2Cu307 = phase and BiC13 q SrI., + CuI for the superconducting phase in the Bi-Sr-Ca-Cu-O system. Furthermore, both studies employed a mixture of O., and H20 as the oxygen source. Typical deposition temperatures were 870-910~ in the Y-Ba-Cu-O system and 800-850~ in the Bi-Sr-Ca-Cu-O system.A thermodynamic investigation of CVD of YBa2Cu3OT. x from the metal precursors YCI3, BaI=, and CuC1 was recently presented (13). The results were found to agree well with the experimental findings (11). The presence of both H20 and O2 was required to deposit the YBa2Cu:~OT_ ~. phase and rather high values of the oxygen source vapor concentration to metal source vapor concentration ratio were found to be necessary. In the present paper, CVD of the superconducting YBa.,Cu30.~_x phase from different halide precursors was thermodynamically investigated. Two different and extreme conditions wer...

Several phases in the Bi-0 system have been deposited by chemical vapor deposition on MgO(00l) substrates.Bismuth iodide, Bi13, and oxygen were used as source materials. An experimental chemical vapor deposition stability diagram has been determined as a function of the deposition temperature and the [02]/BiI,] ratio. Depending on these parameters different phases such as a-Bi,03, 13-Bi203, and Bi20233 were deposited. At low deposition temperatures bismuth oxyiodides (BiOl or Bi5071) were also obtained. For suitable conditions the BiOl phase was found to grow epitaxially on the MgO(001) substrate with the two different orientations [l00}Mgo//[100]eboI and [lO0IMgo//[1lO1B,oI.

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