Atomic layer deposition of Ti-HfO2 dielectrics

J Mater Sci Mater Electron, 2003

Smooth, 4±6-nm thick hafnium oxide ®lms were grown by atomic layer deposition from HfI 4 or HfCl 4 and H 2 O on SiO 2 /Si(1 0 0) substrates at 300 C. Non-uniform ®lms were obtained on hydrogen-terminated Si(1 0 0). The stoichiometry of the ®lms corresponded to that of HfO 2 . The ®lms contained small amounts of residual chlorine and iodine. The ®lms deposited on SiO 2 /Si(1 0 0) were amorphous, but crystallized upon annealing at 1000 C. In order to decrease the conductivity, the HfO 2 ®lms were mixed with Al 2 O 3 , and to increase the capacitance, the ®lms were mixed with Nb 2 O 5 . The capacitance±voltage curves of the Hf±Al±O mixture ®lms showed hysteresis. The capacitance±voltage curves of HfO 2 ®lms and mixtures of Hf±Al±Nb±O were hysteresis free.

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2013

The electrical properties of HfO 2-based metal-insulator-semiconductor capacitors have been systematically investigated by means of I-V and C-V characteristics, admittance spectroscopy, deep level transient spectroscopy, conductance transient, and flat band voltage transient techniques. Attention is also given to the study of the temperature dependence of the leakage current. HfO 2 films were grown on p-type silicon substrates by atomic layer deposition using hafnium tetrakis(dimethylamide) as hafnium precursor, and ozone or water as oxygen precursors. The growth temperature ranged from 150 to 350 C. Low growth temperatures prevent decomposition and high growth rate, as well as high contamination levels. As a result, the leakage current is lower for lower deposition temperatures. Some of the deposited samples were submitted to a postdeposition annealing at 650 C in N 2 atmosphere, showing a decrease in the leakage current and an increase in the equivalent oxide thickness (EOT), whereas interfacial state density increases and defect density inside the dielectric bulk decreases. Regarding dielectric reliability, in our experimental conditions, HfO 2 layers grown at 150 C exhibit the largest EOT and breakdown voltage. The electrical behaviour is clearly linked with structural properties, and especially with the formation of an interfacial layer between the HfO 2 layer and the silicon substrate, as well as with the presence of several impurities. V

Microelectronic Engineering, 2008

Hf-ON and HfO 2 thin films were evaluated as barrier layers for Hf-Ti-O metal oxide semiconductor capacitor structures. The films were processed by sequential pulsed laser deposition at 300°C and ultraviolet ozone oxidation process at 500°C. The as-deposited Hf-Ti-O films were polycrystalline in nature after oxidation at 500°C and a fully crystallized (o)-HfTiO 4 phase was formed upon high temperature annealing at 900°C. The Hf-Ti-O films deposited on Hf-ON barrier layer exhibited a higher dielectric constant than the films deposited on the HfO 2 barrier layer. Leakage current densities lower than 5 Â 10 A/cm 2 were achieved with both barrier layers at a sub 20 Å equivalent oxide thickness.

Hafnium oxide (HfO 2) thin films have been made by radio-frequency (rf) magnetron-sputtering onto Si(1 0 0) substrates under varying growth temperature (T s). HfO 2 ceramic target has been employed for sputtering while varying the T s from room temperature to 500 • C during deposition. The effect of T s on the growth and microstructure of deposited HfO 2 films has been studied using grazing incidence X-ray diffraction (GIXRD), and high-resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive X-ray spectrometry (EDS). The results indicate that the effect of T s is significant on the growth, surface and interface structure, morphology and chemical composition of the HfO 2 films. Structural characterization indicates that the HfO 2 films grown at T s < 200 • C are amorphous while films grown at T s > 200 • C are nanocrystalline. An amorphous-to-crystalline transition occurs at T s = 200 • C. Nanocrystalline HfO 2 films crystallized in a monoclinic structure with a (−1 1 1) orientation. An interface layer (IL) formation occurs due to reaction at the HfO 2 –Si interface for HfO 2 films deposited at T s > 200 • C. The thickness of IL increases with increasing T s. EDS at the HfO 2 –Si cross-section indicate that the IL is a (Hf, Si)–O compound. The electrical characterization using capacitance–voltage measurements indicate that the dielectric constant decreases from 25 to 16 with increasing T s. The current–voltage characteristics indicate that the leakage current increases significantly with increasing T s due to increased ILs.

Thin Solid Films, 2002

Hafnium tetraiodide and oxygen were used as precursors for atomic layer deposition of hafnium dioxide (HfO ) thin films on 2 silicon substrates at temperatures of 400-750 8C. At 500-750 8C the growth rate ranged from 0.11 to 0.12 nmycycle and, within the experimental uncertainty, did not depend on the substrate temperature. With the decrease of the substrate temperature from 500 to 400 8C, however, the growth rate decreased to 0.035 nmycycle. All films contained monoclinic HfO . In addition, some 2 amount of cubic, tetragonal or orthorhombic phase was observed in thinner films, particularly in those deposited at lower substrate temperatures and lower oxygen doses. The relative dielectric constant of the films measured at the frequency of 500 kHz reached 16. ᮊ

Thin Solid Films, 2002

Stoichiometric HfO films were atomic layer deposited from HfI and HfCl at 300 8C on p-Si substrates. Water was in 2 4 4 both cases used as an oxygen precursor. The films consisted dominantly of monoclinic HfO phase. Additional tetragonal HfO 2 2 could be detected only in the films grown from HfCl . Effective permittivities were frequency-independent and varied in the 4 range of 12-14, without clear dependence on the precursor used. Oxide rechargeable trap densities were relatively high for the films grown from HfCl . The films grown from HfI were more resistant against breakdown. The films grown from either 4 4

2003

Thin HfO 2 films have been deposited on silicon via atomic layer deposition using anhydrous hafnium nitrate ͓Hf(NO 3) 4 ͔. Properties of these films have been investigated using x-ray diffraction, x-ray reflectivity, spectroscopic ellipsometry, atomic force microscopy, x-ray photoelectron spectroscopy, and capacitance versus voltage measurements. Smooth and uniform initiation of film growth has been detected on H-terminated silicon surfaces. As-deposited films were amorphous, oxygen rich, and contained residual NO 3 and NO 2 moieties from the nitrate precursor. Residual nitrates were desorbed by anneals Ͼ400°C, however, the films remained oxygen rich. Crystallization of thin films (Ͻ10 nm) occurred at roughly 700°C. For films less than ϳ10 nm thick, the effective dielectric constant of the film and any interfacial layer ͑neglecting quantum effects͒ was found to be in the range of kϳ10Ϫ11. From a plot of electrical thickness versus optical thickness, the dielectric constant of the HfO 2 layer was estimated to be k HfO 2 ϳ12 Ϫ14. Leakage current was lower than that of SiO 2 films of comparable equivalent thickness. The lower than expected dielectric constant of the film stack is due in part to the presence of an interfacial layer ͑likely HfSiO x). Excess oxygen in the films may also play a role in the reduced dielectric constant of the HfO 2 layer.

Journal of Materials Science-materials in Electronics, 2007

Hafnium oxide (HfO2) has emerged as the most promising highkdielectric for MOS devices. As-deposited sputtered HfO2 thin films have large number of defects resulting in increased oxide charge and leakage current. In this paper the effect of sputtering voltage, bias sputtering and post deposition thermal annealing is investigated. The I–V and C–V characteristics of the dielectric film are studied employing Al–HfO2–Si MOS capacitor structure. It is found that oxide charge increases with increasing sputtering voltage. Thermal annealing in oxygen reduces the interface/oxide charges and leakage current. It is shown that applying substrate bias during film deposition leakage current is further reduced by an order of magnitude. The microstructure of thin film is examined by AFM. The reduction in surface roughness with bias sputtering is shown. The experimental results are presented and discussed for device application.

Chemical Vapor Deposition, 2002

HfO 2 films were grown by atomic layer deposition (ALD) from a new liquid precursor, Hf(ONEt 2 ) 4 and H 2 O, at temperatures between 250 C and 350 C on borosilicate glass and Si(100) substrates. The highest growth rate was achieved at 300 C, whereas the growth was essentially slower at 250 C and ceased at 350 C. The films possessed an O:Hf ratio of 2.15 ± 0.12, as determined by ion beam analysis. The films were weakly crystallized, showing X-ray diffraction (XRD) peaks characteristic of monoclinic phase. The refractive index of the films varied between 1.93 and 1.96. The effective permittivities of the dielectric layers in Al/HfO 2 /n-Si(100) capacitor structures were close to 10.

The electrical properties of HfO2/Al2O3 stacked dielectrics on n-type In0.53Ga0.47As were investigated as a function of the atomic layer deposition (ALD) temperature, particularly within the low temperature range from 100 to 200 • C. Although the capacitance equivalent oxide thickness increased due to decreases in the dielectric constants of the HfO2 and the Al2O3 films, lowering the ALD temperature to 100 • C improved the interface-related electrical characteristics, such as the interface state density and frequency dispersion under accumulation. In particular, a significant reduction in the leakage current was achieved at a similar physical thickness under substrate electron injection conditions, which was probably due to the improved near-interface characteristics enabled by the formation of the gate stack at a temperature of 100 • C.