The authors investigated the dielectric constant change of Hf(1−x)SixO2 film as functions of Si concentration and annealing temperature. As a result, the dielectric constant of Hf(1−x)SixO2 was increased when doped with a small amount of Si after 800°C annealing. The authors revealed that the dielectric constant enhancement of Hf(1−x)SixO2 films is related to the phase transformation from the monoclinic to the tetragonal phase of HfO2. By using the Clausius-Mossotti relation, it is concluded that the dielectric constant enhancement through the structural phase transformation is derived from the molar volume shrinkage rather than the molar polarizability increase.

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Articles you may be interested inDetailed leakage current analysis of metal-insulator-metal capacitors with ZrO2, ZrO2/SiO2/ZrO2, and ZrO2/Al2O3/ZrO2 as dielectric and TiN electrodes J. Vac. Sci. Technol. B 31, 01A109 (2013); 10.1116/1.4768791 Impact of bottom electrode and Sr x Ti y O z film formation on physical and electrical properties of metalinsulator-metal capacitors Appl. Phys. Lett. 98, 182902 (2011); 10.1063/1.3584022 Influence of precursor chemistry and growth temperature on the electrical properties of SrTiO 3 -based metalinsulator-metal capacitors grown by atomic layer deposition J. Vac. Sci. Technol. B 29, 01AC04 (2011); 10.1116/1.3525280 Impact of crystallization behavior of Sr x Ti y O z films on electrical properties of metal-insulator-metal capacitors with TiN electrodes Appl. Phys. Lett. 97, 162906 (2010); 10.1063/1.3505323 Atomic-layer-deposited Al 2 O 3 -Hf O 2 -Al 2 O 3 dielectrics for metal-insulator-metal capacitor applications Appl. Phys. Lett.In this work, the physical and electrical properties of Sr x Ti 1−x O y ͑STO͒-based metal-insulator-metal capacitors ͑MIMcaps͒ with various compositions are studied in detail. While most recent studies on STO were done on noblelike metal electrodes ͑Ru, Pt͒, this work focuses on a low temperature ͑250°C͒ atomic layer deposition ͑ALD͒ process, using an alternative precursor set and carefully optimized processing conditions, enabling the use of low-cost, manufacturable-friendly TiN electrodes. Physical analyses show that the film crystallization temperature, its texture and morphology strongly depends on the Sr/Ti ratio. Such physical variations have a direct impact on the electric properties of Sr x Ti 1−x O y based capacitors. It is found that Sr-enrichment result in a monotonous decrease in the dielectric constant and leakage current as predicted by ab initio calculations. The intercept of the EOT vs physical thickness plot further indicates that increasing the Sr-content at the film interface with the bottom TiN would result in lower interfacial equivalent-oxide thickness.

Metastable perovskite SrxTiyOz (STO) films were formed over a wide composition range by crystallization of layers grown by atomic layer deposition. An expansion of the lattice, decrease in permittivity and mild increase in band gap are observed with increasing Sr content. Sr-rich films [Sr/(Sr+Ti)∼62 at. %] show significant improvement in leakage current at low equivalent oxide thicknesses (EOT) as compared to stoichiometric films (Sr/(Sr+Ti) ∼50 at. %). TiN/STO/TiN capacitors with leakage ∼10−6 A/cm2 at 1 V were obtained at 0.6 nm EOT for crystalline Sr-rich STO. The difference in leakage behavior was found to correlate with different microstructures developed during crystallization.

In this work, we discuss doping effects of other metal oxides into HfO2 as a function of annealing temperature or doping concentration, and demonstrate a dramatic change of dielectric properties of doped HfO2 films. In addition to the relative dielectric constant (k-value), crystallization/amorphous characteristics have been also studied. One case induces easier crystallization than the pure HfO2, while the other case keeps amorphous up to 900 ºC without nitrogen introduction. From those observations, we discuss a general guideline for obtaining higher-k dielectric films.

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Hafnium titanate ͑HTO͒ films were deposited within a large Hf-Ti compositional range by atomic layer deposition using HfCl 4 /TiCl 4 /H 2 O precursors. The Hf content of the layers is well controlled by the precursor pulse ratio, as indicated by Rutherford backscattering. The saturation conditions of ternary HTOs are different compared to those of the binary oxides. First-principles simulation confirmed the enhancement of the Hf precursor reactivity in the presence of Ti-OH. Growth curves of HTOs showed a good linearity with the number of reaction cycles. A linear correlation between density, quantified by X-ray reflectometry, and composition was observed. X-ray diffraction indicated that the as-deposited films are amorphous up to 500-700°C, depending on the Hf/Ti ratio. The orthorhombic HfTiO 4 diffraction lines in the samples ͑30-64% Hf͒ annealed at 850°C were observed. For a Hf content higher than 82%, a monoclinic HfO 2 -like structure was reported. The dielectric constant and leakage current depend on the Ti content, the film crystallinity, and the anneal atmosphere. The postdeposition anneal in O 2 is found to have a drastic effect in leakage current density reduction and could be a key for further improvements of HTO electrical properties.Hafnium titanate ͑HTO͒ is studied as a high-k dielectric in metalinsulator-metal ͑MIM͒ capacitors for dynamic random access memory applications to meet the need for continuously increasing permittivity values. HfO 2 shows a moderate permittivity ͑ ϳ 20 to 25͒, a wide bandgap ͑5.6 eV͒, and a thermal stability toward Si/SiO 2 at high temperatures. TiO 2 has a lower bandgap ͑3.0-3.5 eV͒ but displays a higher permittivity, which ranges between 40 and 86. This variation is assigned to the dependence of permittivity on crystalline phase or the presence of low permittivity interfacial layer. 1 Therefore, HTO could present intermediate properties between the binary oxides. In this regard, chemical vapor deposition ͑CVD͒ of Hf x Ti 1−x O 2 thin films with a permittivity of approximately 50 was reported. 2 Other authors report as well on the deposition of HTO via CVD, 3,4 or physical vapor deposition, 5 pulsed laser deposition, 6 dc magnetron sputtering, 7-10 and reactive sputtering. 11 Few reports exist on Hf x Ti 1−x O 2 via atomic layer deposition ͑ALD͒. 12-14 Using Ti͑OCH 3 ͒ 4 , HfCl 4 , and H 2 O as precursors, a permittivity value of 51 at 1 MHz and a leakage current of 8.6 ϫ 10 −5 A/cm 2 at 1 V bias for a Ru bottom electrode were reported. Alternatively, the ALD using TiCl 4 , HfCl 4 , and H 2 O as precursors was presented focusing on film characteristics 12,13 of 8-45% Ti content.In this present study, a series of HTO compositions was prepared by ALD using TiCl 4 , HfCl 4 , and H 2 O precursors and a deposition temperature of 300°C over a wide range of compositions including Ti-rich ones ͑4-70% Ti͒. A typical ALD process occurs in a sequence of metal and oxygen source pulses separated by N 2 purge periods. The reactants are chemisorbed until saturation was reached. Inert g...

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