Thermal stability of hafnium silicate dielectric films deposited by a dual source liquid injection MOCVD

The hafnium and silicon precursors, Hf(NMe₂)₄ and Bu^tMe₂SiOH, have been investigated for the MOCVD of high- hafnium silicate, (HfO₂)_1–x –(SiO₂) _x films for gate dielectric applications. Control of the silica concentration in the hafnium silicate can be achieved by varying the relative precursor ratios up to a saturation level of 35–40% SiO₂. The thermal stability of the resulting hafnium silicate films in air has been investigated using medium energy ion scattering. Internal oxidation of the underlying silicon substrate is discernable when the films are annealed in dry air for 15 min over the temperature range 800–1000 °C.     

Thermal stability of GdScO3 and LaLuO3 films prepared by liquid injection MOCVD

We have studied thermal stability of GdScO₃ and LaLuO₃ films prepared by liquid injection metal-organic chemical vapour deposition (MOCVD). In the present work, we report on the characterization of LaLuO₃ and GdScO₃ thin dielectric films by SIMS and capacitance-voltage (C-V) measurements. In both GdScO₃ and LaLuO₃ films, SIMS analysis revealed the presence of a silicate interfacial layer. The C-V characteristics were found to be shifted after thermal treatment to negative and positive voltages for GdScO₃ and LaLuO₃ films, respectively. Furthermore we have observed that LaLuO₃ films exhibit C-V characteristics more stable to annealing conditions compared with GdScO₃ films.     

Stress control of a-SiC films deposited by dual source dc magnetron sputtering

In the present paper, we show that a-SiC films deposited from two independent Si and graphite magnetron sputtering sources have small tensile stress of ∼100 MPa without post-deposition annealing. Our sputtering apparatus has a rotation substrate holder that is designed to move to the front of individual targets alternately. In this experimental geometry, the relaxation period, when no deposition is made, must be present during sputtering. The presence of this relaxation period is found to be effective to change the compressive internal stress of deposited films into tensile direction. We have also succeeded to fabricate free-standing a-SiC soft X-ray filter with the thickness of 100-600 nm. The transmission spectra of these filters for soft X-ray beam showed good agreement with calculated ones.     

Thermal stability of the phase composition and structure of hafnium diboride films

The thermal stability of the composition and crystal structure of hafnium diboride films grown by rf magnetron sputtering have been studied by X-ray diffraction and secondary ion mass spectrometry. We have assessed the effect of high-temperature annealing in air on the phase composition and structure of the hafnium diboride films. The results demonstrate that annealing produces a HfO₂ oxide layer on the surface of the HfB₂ film. Raising the annealing temperature from 600 to 1000°C leads to an increase in the thickness of the oxide layer from 100 to 600 nm and to the formation of a multilayer HfB₂-HfO₂ coating.     

Carbonaceous alumina films deposited by MOCVD from aluminium acetylacetonate: a spectroscopic ellipsometry study

Spectroscopic ellipsometry was used to characterize carbonaceous, crystalline aluminium oxide films grown on Si(100) by low-pressure metal organic chemical vapour deposition, using aluminium acetylacetonate as the precursor. The presence of carbon in the films, attributed to the use of a metalorganic precursor for the deposition of films, was identified and analysed by secondary ion mass spectroscopy and X-ray photoelectron spectroscopy, for the elemental distribution and the chemical nature of the carbon in the films, respectively. Ellipsometry measurements over the photon energy range 1.5–5 eV were used to derive the pseudo-dielectric function of the aluminium oxide-containing films. Multi-layer modelling using linear regression techniques and the effective medium approximation were carried out to extract the structural details of the specimens. The excellent fit between the simulated and experimental optical data validates the empirical model for alumina-containing coatings grown by MOCVD.     

Conformal growth and characterization of hafnium silicate thin film by MOCVD using HTB (hafnium tertra-tert-butoxide) and TDEAS (tetrakis-diethylamino silane)

Hafnium silicate (HfSi _x O _y ) films were deposited by metal-organic chemical vapor deposition (MOCVD) using hafnium tetra-tert-butoxide [HTB, Hf(OC(CH₃)₃)₄] and tetrakis-diethylamino silane [TDEAS, Si(N(C₂H₅)₂)₄]. The grown Hf-silicate films showed Hf-rich composition and impurity concentrations less than 1 atomic % (below detection limits). Uniformly deposited films with good step-coverage were obtained on hole-patterned SiO₂ substrates. Hafnium silicate films had stable amorphous crystalline structure up to 800 °C annealing and above 900 °C, a tetragonal HfO₂ crystal phase was observed. Dielectric constant (k) of the Hf-silicate films was about 15 and flat band voltage (V _fb) and hysteresis were very low.     

双离子束溅射法制备铁氮薄膜

使用双离子束溅射法制得了铁氮薄膜,随着基片温度的变化,薄膜的成分是ε－Fe2-3N,γ′－Fe4N或是二相的混合物,薄膜的晶粒尺寸随基片温度的升高而增大。以振动样品磁强计（VSM）测定了薄膜的磁性能。另外,研究了在基片温度为160℃时,改变主源中通入N2／Ar的比例对薄膜成分的影响。     

Anomalous optical absorption in dielectric thin films deposited by electron bombardment

The advantages of electron bombardment sources over conventional resistance-heated ones for the deposition of dielectric films can occasionally be outweighed by the occurrence of anomalous optical absorption.Work is described which attempts to identify the cause of this unwanted absorption. A charge analyser was developed which showed that relatively large electron currents can accompany the vapour stream emanating from this type of source. The resulting electron bombardment of the substrate during film deposition apparently gives rise to “colour centre” types of absorption phenomena in the condensed film. Although the mechanism of this process is not fully understood, experimental results are presented which demonstrate the importance of the effect in optical coating technology and show how the absorption can be either eliminated or enhanced by controlling the deposition conditions.     

Electrochemically deposited sol-gel-derived silicate films as a viable alternative in thin-film design

Sol-gel-derived silicate films were electrochemically deposited on conducting surfaces from a sol consisting of tetramethoxysilane (TMOS). In this method, a sufficiently negative potential is applied to the electrode surface to reduce oxygen to hydroxyl ions, which serves as the catalyst for the hydrolysis and condensation of TMOS. The electrodeposition process was followed by the electrochemical quartz crystal microbalance and cyclic voltammetry. The electrodeposited films were characterized for their surface morphology, porosity, and film thickness using atomic force microscopy, electrochemical probe techniques, surface area and pore size analysis, and profilometry. The electrodeposited films were found to have a completely different surface structure and to be significantly rougher relative to spin-coated films. This is likely due in part to the separation of the gelation and evaporation stages of film formation. The electrodeposited films were found to be permeable to simple redox molecules, such as ruthenium(III) hexaammine and ferrocene methanol. Film thickness can be easily varied from < 75 nm to > 15 microm by varying the electrode potential from -600 mV to more than -1000 mV, respectively. The electrodeposition process was further applied for the electroencapsulation of redox molecules and organic dyes within the silicate network. Cyclic voltammograms for the gel-entrapped ferrocene methanol (FcCH2OH) and ruthenium(II) tris(bipyridine) (Ru(bpy)3(2+)) exhibited the characteristic redox behavior of the molecules. The electroencapsulation of organic dyes in their "native" form proved to be more difficult because these species typically contain reducible functionalities that change the structure of the dye.     

Synthesis and characterization of hafnium tert-butylacetoacetate as new MOCVD precursor for HfO2 films

A new hafnium β-ketoesterate Hf(tbob)₄ (tbob=tert-butyl-3-oxobutanoate or tert-butylacetoacetate) was obtained by ligand exchange reaction applied to Hf₂(OⁱPr)₈(ⁱPrOH)₂. It was characterized by elemental analysis, FT-IR, ¹H NMR, mass-spectroscopy and TGA. The compound is volatile and it was tested for the growth of HfO₂ films on Si(100) and R-plane sapphire substrates at 600–800 °C by pulsed liquid injection MOCVD. The films were characterized by XRD, XPS and AFM. Stoichiometric amorphous films were obtained on silicon, while those on sapphire were relatively well crystallized (00l) monoclinic. The growth was kinetically limited in all the temperature range studied (600–800°C).     

Mechanical and thermal properties of physical vapour deposited alumina films Part I Thermal stability

Thermal stability of non-reactive physical vapour deposited alumina films of varying thickness on Al₂O₃-TiC and Si substrates, deposited at two different substrate biases, is examined. Substrate curvature measurements were used to determine the deposition stress and stress development during thermal cycling and annealing. Thermal cycling experiments revealed that the films deposited on Al₂O₃-TiC substrates become irreversibly more compressive on heating and annealing while films deposited on Si substrates become irreversibly more tensile. The deposition stress was found to be independent of film thickness, substrate material, and substrate bias during deposition. The thermal stability was independent of film thickness and substrate bias during deposition.     

Radio frequency source power effect on silicon nitride films deposited by a room-temperature pulsed-PECVD

Silicon nitride (SiN) films deposited by using a pulsed-plasma enhanced chemical vapor deposition system at room temperature were investigated as a function of radio frequency source power and duty ratio in the experimental ranges of 200-800 W and 40-90%, respectively. Diagnostic parameters, measured using a non-invasive ion energy analyzer, were related to SiN deposition rate. Decreasing the source power increased high ion energy, but decreased low ion energy. A high similarity between ion energy flux and ion energy was observed. Decreasing the source power increased the deposition rate for all duty ratios. For all the variations in the power and duty ratio, the deposition rate varied in the range of 290-640 Å/min. Decreasing the duty ratio was effective in increasing the deposition rate. The deposition rate was strongly correlated to high ion energy and high ion energy flux as a function of source power.     

The effect of WO3 source stability on the properties of films deposited by electron beam deposition

This study investigates the impact of high temperature and vacuum on the properties of WO₃ powder during electron beam deposition and evaluates the consequential effects on the as-deposited films. Therein, the grain size and the crystallinity of the source were observed to increase and become non-stoichiometric tungsten oxide (WO_3−x) due to the high temperature and vacuum during the first deposition. As a result of these changes in the source, the optical band gap, E_g, of the deposited film decreased from 3.11 eV to 3.07 eV, and the absorbance was observed to increase. The coloration efficiencies of the deposited films decreased from 23 to 16 cm² C⁻¹. WO₃-incorporated carbon nanotubes (WO₃/CNT) were observed in the source after electron beam deposition if there were some initial carbon impurities in the source prior to deposition.     

Investigation of alumina-silica films deposited by pulsed injection metal-organic chemical vapour deposition

This work is devoted to deposition of alumina-silica films using an innovative pulsed injection metal organic chemical vapour deposition technique and aluminium tri(iso-propoxide) (Al(i-OPr)₃) and tetraethoxysilane (TEOS) as precursors. The deposited aluminium silicate films have been characterised by scanning electron microscopy, infrared spectroscopy, X-ray diffractometry and capacitance-voltage (C-V) measurements. The investigation of the deposition at different Si/Al ratios and substrate temperatures has shown that the growth rate increases with the increase of Al(i-OPr)₃ proportion in solution and decreases as the proportion of TEOS increases. We have also shown that aluminium content in the film increases at lower deposition temperatures while silicon content increases at higher temperatures. The permittivity of the films determined from C-V measurements decreases with increasing substrate temperature. It was found that films deposited at substrate temperatures of 600 or 700 °C and with the highest Si/Al ratio have the lowest dielectric permittivity. This research should be useful for further development of MOCVD technology for the deposition of aluminosilicate-based dielectric materials with controlled dielectric permittivity.     

Effect of precursor ratio on the structural properties of ZnO thin films deposited by low pressure MOCVD

The effect of precursor ratio (H2O/DEZ) on the texture orientation, surface morphology, optical transparency and electrical resistivity of ZnO thin films deposited by MOCVD was investigated. Deposition temperature and pressure were fixed at 120 degrees C and 0.67 torr, respectively. The precursor ratio was varied between 0.1 and 4. It was found that the texture orientation changed from (0002) to (1120) with increase of the precursor ratio. (1120) textured film shows well facetted tetrapod like rough surface morphology, which scatters the incident light very effectively. The electrical resistivity was in the range of about 0.1 omega cm in the undoped state, which was found to decrease with increase of the film thickness and decrease of the precursor ratio.     

Physical properties of erbium implanted tungsten oxide films deposited by reactive dual magnetron sputtering

Amorphous and partially crystalline WO₃ thin films were prepared by reactive dual magnetron sputtering and successively implanted by erbium ions with a fluence in the range from 7.7 × 10¹⁴ to 5 × 10¹⁵ ions/cm². The electrical and optical properties were studied as a function of the film deposition parameters and the ion fluence. Ion implantation caused a strong decrease of the resistivity, a moderate decrease of the index of refraction and a moderate increase of the extinction coefficient in the visible and near infrared, while the optical band gap remained almost unchanged. These effects could be largely ascribed to ion-induced oxygen deficiency. When annealed in air, the already low resistivities of the implanted samples decreased further up to 70 °C, whereas oxidation, and hence a strong increase of the resistivity, was observed at higher annealing temperatures.     

类金刚石碳膜的热稳定性

总结了各种ＤＬＣ膜的热稳定性及分析手段,概述了加热退火情况下ＤＬＣ膜结构,内应力的变化,评述了国内的最新研究进展,并提出了有等进一步研究的问题。     

Electrochemical properties of dielectric films of aluminium oxide deposited on silicon

Chemical, physical and some electrical properties of aluminium oxide dielectric films deposited on silicon substrates are reported. In the growth of these films we utilized the vapour phase reaction of the hydrolysis of aluminium trichloride (AlCl₃) in an r.f. heated horizontal reactor tube to give films of good thickness uniformity and run-to-run consistency. The activation energies associated with the constituent components of this complex chemical reaction were determined. It is shown that the films exhibit high dielectric constant (7.7±0.2) and field strength (in excess of 6 × 10⁶ V cm^?1) with low ionic content (typically anout 10¹⁰ cm^?2), making them an attractive contender for passivation and for use as the gate dielectric of metal-insulator-semiconductor (MIS) devices.     

Evaluation of hafnium nitride thin films sputtered from a hafnium nitride target

Hafnium nitride (HfN) thin films were prepared on Si (100) substrates by radio frequency magnetron sputtering with a compound target. Nitrogen composition, work function and electrical resistivity were investigated to evaluate thin film properties. Nitrogen composition and work function had little dependence on argon gas pressure and radio frequency power. Electrical resistivity showed strong correlation with the substrate temperature. When thin films were fabricated at room temperature, the electrical resistivity was 100 μΩ cm, and it became lower with an increase in the substrate temperature. When the films were fabricated at 600 °C, the resistivity became less than 50 μΩ cm.