Metalorganic Chemical Vapor Deposition Method Research Articles

Deposition of silicon carbide films using a high vacuum metalorganic chemical vapor deposition method with a single source precursor: Study of their structural properties

Silicon carbide (SiC) thin films were prepared on Si(100) substrates by high vacuum metalorganic chemical vapor deposition using a single-source precursor at various growth temperatures in the range of 700–1000 °C. The precursor is diethylmethylsilane, and is used without carrier gas. The effects of substrate temperature as well as deposition time on the crystal growth were investigated. The optimum temperature for the formation of high quality polycrystalline SiC thin films was found to be 900 °C on the basis of x-ray diffraction and transmission electron diffraction results. X-ray photoemission spectroscopy shows that SiC films grown at 900 °C have slightly carbon-rich compositions (Si:C=1:1.2) in the surface region, but stoichiometric composition in the bulk. Scanning and transmission electron microscope images show the influence of substrate temperature on the grain size and crystallinity of the films. Large grain sizes and high quality crystallinity can be obtained below 900 °C.

A comparative study of microstructure of RuO 2 nanorods via Raman scattering and field emission scanning electron microscopy

Raman scattering (RS) and field emission scanning electron microscopy (FESEM) have been used to extract microstructural information of RuO 2 nanorods (NRs) and a two-phase system comprising NRs embedded in polycrystalline matrix deposited on different substrates by the metal-organic chemical vapor deposition method. The red shifts and asymmetric broadening of the Raman line shape for the NRs are analyzed by the spatial correlation model. The deduced spatial correlation length l is found to be much smaller than that of the average size L 0 estimated from the FESEM images. The Raman features for the two-phase system can be resolved into two parts: a Lorentzian line shape feature corresponding to the polycrystallite at higher frequency side and an asymmetrically broadened NRs' signature located at lower frequency end. The volume fraction of NRs in the two-phase system can be determined from the analysis. These results demonstrate the significance of RS as a structural characterization method when used in conjunction with FESEM.

Aligned TiO2 Nanorods and Nanowalls.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Preparation and Characterization of RuOx Thin Films by Liquid Delivery Metalorganic Chemical Vapor Deposition

RuOx films were deposited by liquid delivery metalorganic chemical vapor deposition method using a new Ru(C8H13O2)3 precursor for the advanced capacitor electrode in Gbit-scale dynamic random access memory. Deposition was carried out on a TiN barrier layer in the range of 250–400°C and the ratio of the O2 flow rate to the total flow rate of Ar and O2 was varied from 20 to 80%. RuOx thin films were annealed at 650°C for 1 min with Ar, N2 or NH3 ambient. Film characterization was performed in terms of resistivity, crystal structure, surface morphology, microstructure and film purity. The resistivity depended on the impurity, grain density and crystalline structure of the film. The oxygen used to form Ru the oxide was found to eliminate the carbon and hydrogen elements in an organic source. The O2 flow ratio that changes the crystal structure of the films from Ru to RuO2 was found to be 40%. The metallic Ru phase forming a RuO2/Ru bilayer at the RuO2/TiN interface was observed at O2 flow ratios of 50% and 60%. The X-ray diffraction results indicate that the RuO2 phase and the silicidation are not observed regardless of the ambient gases. Ar was more effective than N2 and NH3 as an ambient gas for the postannealing of the Ru films.

Deposition of epitaxial silicon carbide films using high vacuum MOCVD method for MEMS applications

Silicon carbide (SiC) thin film have been prepared on both Si(100) and SiO 2 patterned Si(100) substrates by the high vacuum metal-organic chemical vapor deposition (MOCVD) method using a single source precursor at various growth temperatures in the range of 700–1000 °C. Diethylmethylsilane(DEMS) was used as precursor without carrier gas. The effects of substrate temperature as well as deposition time on the crystal growth and hardness were mainly investigated in this study. The optimum temperature for the formation of the epitaxial SiC thin films were found to 900 °C on the basis of XRD results. However, the XPS result shows that the SiC film grown at 900 °C have carbon rich (Si:C=1:1.2 composition) surface due to surface reaction of the precursor itself. From the SEM images, substrate temperature has influence on the grain size and crystallinity of the SiC films. Especially, the major crystal form of these deposited films was rectangular in shape on the substrates at 900 °C. We also obtain a high hardness SiC thin film with 32 GPa.

Effect of dislocations on luminescence properties of silicon-doped GaN grown by metalorganic chemical vapor deposition method

The effect of dislocations on the structural and electro-optic characteristics of n-GaN has been studied. X-ray diffraction, Hall measurement, photoluminescence spectroscopy, Raman spectroscopy, and transmission electron microscopy (TEM) have been performed to understand the interdependence of strain, dislocation, and doping concentration. The most remarkable observation of the study is the blueshift observed at a doping level ND∼1018 cm−3 as a result of the relaxation of strain. The TEM results reveal a higher dislocation defect density at lower doping levels (∼1017 cm−3) than at moderate doping levels. Blueshift is found to result from the redistribution of the dislocation density due to the reduction in strain at a certain optimum doping level(s). This distribution of the dislocation is such that there are virtually no dislocations at some locations, as evident from the sample MD27 with doping ⩾1018 cm−3.

Aligned TiO2 Nanorods and Nanowalls

Well-aligned rutlie and anatase TiO2 nanorods as well as anatase TiO2 nanowalls have been synthesized using a template- and catalyst-free metalorganic chemical vapor deposition (MOCVD) method. Stru...

The Effect of Iridium Bottom Electrode on the Characteristics of Pb(Zr,Ti)O3 Films Grown by MOCVD Method

A novel method of metal-organic chemical vapor deposition (MOCVD) Pb(Zr,Ti)O3 (PZT) has been developed for use in high-density ferroelectric memory device. Well-aligned polycrystalline PZT films were grown onto Iridium bottom electrode by the MOCVD method with tmhd-family precursors in octane-based solvent under oxygen atmosphere at 550°C. Moreover, crystallinity of the PZT films on Ir bottom electrode was improved dramatically by inserting TiAlN barrier layer. It is also investigated the Iridium bottom electrode effect on the PZT in the ways of roughness, grain size, remnant polarization, fatigue and retention properties. Resultantly, highly reliable (111)-oriented PZT capacitors were obtained with 2Pr of 45 μC/cm2 and Vc of 0.8 V through MOCVD method and the interface engineering of the Iridium bottom electrode.

Low Temperature Synthesis of AlN Films by ICP-Assisted Metalorganic Chemical Vapor Deposition Method

AlN thin films were synthesized using induction-coupled plasma (ICP) chemical vapor deposition process. The material characteristics, especially the surface morphology and the texture characteristic, for the AlN thin films were observed to vary with processing parameters markedly. Formation of (110) textured AlN thin films is facilitated when the growth rate is lowered by reducing the flow rate of Ar/NH3 gases. The optical refractive index of the crystalline AlN thin films, (n)c = 1.8899–2.0294, is larger than that for amorphous ones (n)a = 1.7826. Moreover, the n-value for (110) textured AlN thin films is slightly larger than that for randomly oriented ones, which render that the textured and randomly oriented AlN thin films to be a good core/cladding materials system for a planar optical waveguides.

Defects in GaN Films Grown on Si(111) Substrates byMetal-Organic Chemical Vapour Deposition

We report the transmission-electron microscopy study of the defects inwurtzitic GaN films grown on Si(111) substrates with AlN buffer layersby the metal-organic chemical vapour deposition method. TheIn0.1Ga0.9N/GaN multiple quantum well (MQW) reduced thedislocation density by obstructing the mixed and screw dislocationspassing through the MQW. No evident reduction of the edge dislocationsdensity by the MQW was observed. It was found that dislocations withscrew component can be located at the boundaries of sub-grains slightlyin-plane misoriented.

Growth parameters effect on the thermoelectric characteristics of Bi 2Se 3 thin films grown by MOCVD system using Ditertiarybutylselenide as a precursor

The growth of Bi 2Se 3 thin films by metalorganic chemical vapour deposition (MOCVD) using Trimethylbismuth (TMBi) and a novel Se-precursor: Ditertiarybutylselenide (DTBSe) as bismuth and selenium sources, respectively, is investigated on pyrex substrates. The effect of the growth parameters such as substrate temperature, T g, and TMBi partial pressure, P TMBi, on the structural, electrical and thermoelectrical properties for the following growth conditions: 440°C⩽ T g⩽475°C, 0.5×10 −4 atm⩽ P TMBi⩽1×10 −4 atm and a total hydrogen flow rate D T=3 l/mn, of Bi 2Se 3 films has been investigated. The crystallinity versus growth condition ( T g, P TMBi) using X-ray diffraction was studied and a typical preferential c-orientation was observed. Thus, these layers always displayed n-type conduction using Hall effect measurement. The best electric and thermoelectric characteristics under the optimal growth conditions have been found; μ>250 cm 2/V s, ρ⩽11.8 μΩ m and α=–163.7 μV/K Then, These initial results suggest a significant potential for the MOCVD method to produce good thermoelectrical materials using DTBSe as Se-precursor.

Evaluation of Band-Gap Energies and Characterization of Nonradiative Recombination Centers of Film and Bulk GaN Crystals

We have measured photothermal spectra of bulk and film GaN crystals by the photothermal divergence (PTD) method in the temperature range from 110 K to 320 K. The band-gap energy of the GaN film grown by metalorganic chemical vapor deposition (MOCVD) method on a sapphire substrate shifts toward a higher energy because of the stress, compared with that of the bulk GaN grown by hydride vapor-phase epitaxy (HVPE) method. Moreover, the dependence of the PTD signal intensity, IPTD, on the doping has been observed. From IPTD spectra, we have found that a doping procedure may induce the degradation of the crystalline quality of GaN. For the bulk, two peaks in the energy region below the band edge have been observed in the IPTD spectra, and it has been found that such peaks may originate in nonradiative recombination centers. The two peaks have been characterized to be related to deep levels observed previously by means of the so-called deep-level transient-scan method.

Deposition and Characterization of High Dielectric Thin Films for Memory Device Application

(Pb,La)TiO 3 (PLT) and Pb(Zr,Ti)O 3 (PZT) thin films were deposited on Pt/SiO2/Si substrate by metal-organic chemical vapor deposition (MOCVD) using a solid delivery system. The domain configurations of the deposited PLT thin films were investigated, and the film with a columnar structure exhibited a very stable write/read operation for the domain memory application. Electrical properties of PLT, PZT and rf-sputter-deposited (Ba,Sr)TiO 3 (BST) thin films were measured, and their conduction mechanisms were analyzed. The composition and thickness uniformity of BST thin films deposited by the low temperature MOCVD method on a patterned wafer with 0.15 μm-diameter contact holes were investigated, and complete thickness and composition uniformity were obtained especially for the case of a dome-wall-type chamber with a wall temperature of 450°C.

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.

Selective growth of TiO2 thin films on Si(100) surfaces by combination of metalorganic chemical vapor deposition and microcontact printing methods

We successfully patterned TiO2 thin films by metalorganic chemical vapor deposition (MOCVD) on Si(100) substrates where the surface was first modified by an organic thin film. The organic thin film [octadecyltrichlorosilane (OTS)] of self-assembled monolayers (SAMs) was deposited by microcontact printing. Selective deposition of a 130 nm thick TiO2 film was done on a 300–500 °C surface prepared by MOCVD without any carrier or bubbler gas. Auger electron spectroscopy and x-ray diffraction analyses showed that the deposited TiO2 material was stoichiometric, polycrystalline, and consisted of anatase phase. Alpha-step profile and optical-microscopic images also showed that the boundaries between the OTS SAMs and selectively deposited TiO2 thin film areas are definite and sharp. Capacitance–voltage measurement of a TiO2 thin film yielded a dielectric constant of 29, suggesting possible application to electronic materials.

Microstructure of GaN films grown on Si(1 1 1) substrates by metalorganic chemical vapor deposition

We report the transmission electron microscopy (TEM) study of the microstructure of wurtzitic GaN films grown on Si(1 1 1) substrates with AlN buffer layers by metalorganic chemical vapor deposition (MOCVD) method. An amorphous layer was formed at the interface between Si and AlN when thick GaN film was grown. We propose the amorphous layer was induced by the large stress at the interface when thick GaN was grown. The In 0.1Ga 0.9N/GaN multiple quantum well (MQW) reduced the dislocation density by obstructing the mixed and screw dislocations from passing through the MQW. But no evident reduction of the edge dislocations by the MQW was observed. It was found that dislocations located at the boundaries of grains slightly in-plane misoriented have screw component. Inversion domain is also observed.

Characterization of growth behavior and structural properties of TiO 2 thin films grown on Si(1 0 0) and Si(1 1 1) substrates

To comparative study on the growth behavior and structural properties of thin films, in this work, we have deposited the titanium oxide (TiO 2) thin films on both Si(1 0 0) and Si(1 1 1) substrates using a single molecular precursor by metal-organic chemical vapor deposition method at temperature in the range of 600–750 °C and working pressure of 1.0×10 −5 Torr. X-ray diffraction and transmission electron diffraction data suggest that the main film growth directions are [1 1 0] on Si(1 0 0) and [2 0 0] on Si(1 1 1), respectively, indicating that the film growth direction is highly affected by Si wafer orientation. Atomic force microscope and transmission electron microscope images showed that a TiO 2 film deposited on Si(1 0 0) at 750 °C at 1.0×10 −5 has more smooth surface than that grown on Si(1 1 1) under the same deposition condition. The as-grown TiO 2 films were also investigated using Rutherford backscattering spectroscopy (RBS) and secondary ion mass spectroscopy (SIMS) for detail analysis of relationship between film composition and impurity. RBS analysis showed that the as-grown TiO 2 films on both Si(1 0 0) and Si(1 1 1) have nearly stoichiometric composition. Different contamination level, especially hydrogen and carbon, of the TiO 2 films grown on either Si(1 0 0) or Si(1 1 1) substrates have been determined by SIMS analysis.

Texture and surface analysis of NiO buffer deposited on biaxially textured Ni tapes by a MOCVD method

NiO buffer layers for YBCO coated conductors were deposited on textured Ni substrates by a metal-organic chemical vapor deposition(MOCVD) method. Processing variables were the oxygen partial pressure and substrate temperature. The degree of texture and the surface roughness of the deposited NiO surface were analyzed by X-ray pole figure, atomic force microscopy (AFM), and scanning electron microscope (SEM). The (200) textured NiO layer was formed at 450 /spl sim/ 470 /spl deg/C and oxygen partial pressure of 1.67 Torr. Out-of-plane(/spl omega/-scan) and in-plane(/spl Phi/-scan) texture were 10.34/spl deg/ and 10.00/spl deg/, respectively. The surface roughness estimated by atomic force microscopy was in the range of 3.1 /spl sim/ 4.6 nm which was much smoother than that prepared by an oxidation method. We discuss the development of the (200) texture in the MOCVD-NiO films in terms of processing variables.

Deposition of CeO/sub 2/ buffer layers for YBCO coated conductors on biaxially textured Ni substrates by MOCVD technique

CeO/sub 2/ buffer layers for YBa/sub 2/Cu/sub 3/O/sub 7/(YBCO) coated conductors were deposited on biaxially textured Ni substrates by metalorganic chemical vapor deposition (MOCVD) method. The variables were the oxygen partial pressure (P/sub O2/), deposition temperature and time. The [200] texture of CeO/sub 2/ was formed at T = 500 /spl deg/C - 520 /spl deg/C, t = 3 - 15 min and P/sub O2/ = 2.30 torr, while the [111] and [200] texture were competitively formed at other condition. The surface roughness of CeO/sub 2/ films was as good as 5 - 15 nm up to 500 /spl deg/C, while it rapidly increased as a result of grain growth of the CeO/sub 2/ at T /spl ges/ 520 /spl deg/C. The surface roughness of the CeO/sub 2/ films also increased as the deposition time increased. The growth rate of the CeO/sub 2/ films at T = 520 /spl deg/C and P/sub O2/ = 2.30 torr was 200 nm/min, which is much higher than those prepared by other physical deposition methods.

Raman and photoluminescence of ZnO films deposited on Si (111) using low-pressure metalorganic chemical vapor deposition

The highly c-oriented ZnO films were epitaxially grown on n-type Si (111) substrate at the temperature range of 340–460 °C using the low-pressure metalorganic chemical vapor deposition method. All films exhibit a pronounced (002) peak for ZnO, indicative of the strong c-axis oriented characteristic. The ZnO film grown at 400 °C shows the best structural quality along with the largest lateral grain size, well supported by the narrowest full width at half maximum of ZnO (002) peak about 0.19° in x-ray diffraction. However, the temperature dependence of the vibrational modes at 436 and ∼563 cm−1 in Raman spectra revealed a low density of oxygen vacancies in the films grown at low temperatures, which is supposed to determine the photoluminescence (PL) properties. At low temperatures, the narrow ultraviolet (UV) near band emission dominated the PL spectrum with a very weak low energy tail near the band. High temperature (up to 460 °C) would cause serious oxygen deficiency, resulting in the weak broad UV band with obvious blue band emission.