The influence of titanium nitride sputter deposition temperature on surface-hardened 2.5% silicon iron

Surface-hardened silicon iron (SiFe), with 2.5% Si, was sputter deposited with TiN by a reactive d.c. magnetron sputtering process. In this work we have studied the influence of the substrate temperature on the adhesion, hardness and the chemical composition of the TiN film and the substrate hardened structure during sputtering. Glow discharge optical spectrometry (GDOS) and electron microprobe analysis (EPMA), together with a scratch tester and a Vickers' hardness instrument, were used to study the chemical composition depth profiles, hardness and the critical load C_L at the TiN-substrate interface. The substrate surface hardness drops from 820 to 225 HV after TiN deposition as a result of decarburization of the SiFe surfaces. This drop in hardness level was found for all the substrate deposition temperatures, between 200 and 600 °C. The TiN surface hardness reached a maximum of 2700 HV at a substrate temperature of 300 °C and dropped to 1400 HV for a substrate temperature of 600 °C. At 200 °C substrate temperature the TiN surface hardness is 2100 HV which is considered to be a normal hardness for stoichiometric TiN film. GDOS chemical composition depth profiles show changes in the relative intensities at the interface when the substrate deposition temperature was at 400 and 550 °C for the elements carbon, nitrogen, titanium, silicon and iron. The O:Ti ratio increases from 200 to 300 °C and decreases between 300 and 500 °C. Above 500 °C, O:Ti starts to increase again. EPMA shows that the TiN surface hardness and critical load values reach a maximum when the interface C:Ti ratio is 0.1 at a deposition temperature of about 300 °C.     

Reduction of carbon impurities in silicon oxide films prepared by rf plasma-enhanced CVD

Silicon oxide films were deposited at near room temperature by a remote-type radio frequency plasma-enhanced chemical vapor deposition using a mixture of tetramethoxysilane and oxygen as source gas. The temperature of the reactor wall was controlled from 25 to 150°C. Carbon impurities which existed as Si–CH₃ in the deposited films were reduced markedly when the substrate temperature was kept higher than the wall temperature during deposition. The optimum substrate temperature was 50°C to obtain carbon-free silicon oxide films at a wall temperature of 30°C. X-Ray photoelectron spectroscopic analyses of the films proved that carbon impurities existed only on the film surfaces.     

Growth, selectivity and adhesion of CVD-deposited copper from Cu (hexafluoroacetylacetonate trimethylvinylsilane) and dichlorodimethylsilane

Copper films have been deposited by low-pressure (1–20 mTorr) chemical vapour deposition using Cu¹⁺ (hexafluoroacetylacetonate) trimethylvinylsilane onto SiO₂ patterned substrates having seed layers of W, TiN and Al. Blanket deposition is observed for all growth temperatures in the range 140 °C ≤ T_g ≤ 240 °C. However, depending on the initial substrate seed layer and pre-treatment, the relative strength of the copper-oxide and copper-seed layer bond can be dramatically altered particularly when growth is carried out in the presence of dichloromethylsilane (DCDMS). The degree of selectivity as well as film morphology is also found to be sensitive to the initial pre-treatment, growth temperature and flow rate of DCDMS.     

Titanium nitride deposition on hardened high speed steel by reactive magnetron sputtering

Hardened W-Mo-Co high speed steel SIS-2723 (Swedish standard) used for the manufacture of cutting tools was deposited with titanium nitride by reactive magnetron sputtering. In this work we have studied the influence of the substrate deposition temperature on the chemical composition, hardness and adhesion at the interface and in the bulk of the TiN film.

At an approximately 400°C deposition temperature the critical load C_L is at maximum. At the TiN film-substrate interface and at a 400°C deposition temperature it was also found that the ratios Si:N, C:N, C:Ti, Mo:N and Cr:N are at maxima and N:Ti is at a minimum. At a 200°C deposition temperature the O:Fe ratio at the interface is at a maximum and between 400 and 500°C this ratio is at a minimum. The titanium nitride surface hardness as well as the ultramicrohardness in cross-section reach maxima at a 400°C deposition temperature. Further analysis of the TiN film adhesion shows that it is adhesive at deposition temperatures below 350°C and cohesive at higher temperatures.     

Studies using AFM and STM of the correlated effects of the deposition parameters on the topography of gold on mica

A systematic study of the correlated effects of deposition temperature, film thickness and deposition rate on the morphology of gold films on mica was carried out using atomic force microscopy and scanning tunnelling microscopy. For the range of thicknesses, rates and temperatures concerned, a variety of surface structures, mainly in the form of rounded mounds, islands, long channel and short channel plateaux topographical features were formed under various combinations of these three parameters. The rounded mounds and islands formed, respectively, on the mica substrate at room temperature and at 150°C were found to be essentially independent of the film thickness and deposition rate selected. When deposited at higher temperatures (300°C and 440°C), a change from islands to channelled features, via the growth and coalescence of the islands, was observed either on increasing the film thickness for a given deposition rate (≈ 1.0 Å s⁻¹) or on increasing the deposition rate to a given film thickness (400 Å). It is evident from the results presented that, whereas the film thickness and the deposition rate at a given temperature determine to what extent the film has coalesced, the growth temperature influences the lateral size of the surface features formed. In consequence, conducting films were found when the gold coverage was ≥ ≈0.9. Investigation of the vertical characteristics of the films was also conducted. The origin of all the phenomena observed can be attributed to competition between secondary nucleation and thermally enhanced diffusion processes occurring on the gold surface during deposition and film formation.     

Diffusion barrier property of TiN and TiN/Al/TiN films deposited with FMCVD for Cu interconnection in ULSI

Flow modulation chemical vapor deposition (FMCVD) with titanium tetrachloride (TiCl₄) and ammonia (NH₃) is effective for depositing titanium nitride (TiN) films with conformal morphology, good step coverage, low electrical resistivity, and low chlorine residual contamination. It means that FMCVD TiN film is a good candidate of diffusion barriers for copper interconnection technology in ULSI. But the diffusion barrier property of FMCVD TiN film against Cu diffusion has not been confirmed. So, firstly, we deposited Cu (100 nm)/FMCVD TiN (25 nm)/Si multilayer films and investigated the thermal stability of Cu/TiN/Si structure. Vacuum annealing was done at 400, 500, 550 and 600 °C. For films annealed for 30 min at 400 °C, Cu diffused through the TiN layer and formed copper silicides on the surface of Si substrates. Therefore, FMCVD films formed under such conditions are unsatisfactory diffusion barriers. To enhance the diffusion barrier property of FMCVD TiN films, we used sequential deposition to introduce a monolayer of Al atoms between two TiN films. Etch-pit tests showed that for TiN films with Al interlayer, Cu diffusion through the barrier occurred at 500 °C and that is 100 °C higher than TiN film without Al interlayer. Al atoms formed AlO_x with oxygen atoms present in the TiN films as impurities, and fill up the grain boundaries of TiN film, thereby blocking the diffusion of Cu atoms.     

Epitaxial growth of SrTiO3 films with different orientations on TiN buffered Si(001) by pulsed laser deposition

Epitaxial SrTiO₃ (STO) films have been grown on TiN buffered Si(001) by pulsed laser deposition. The TiN layer was in situ deposited at 540, 640 or 720°C whereas the STO film was grown at a fixed temperature of 640°C. We have studied the effect of the growth temperature of TiN on the epitaxial relationship of STO/TiN heterostructures. It is found that for TiN grown at 540 or 640°C the epitaxial relationship is 001STO 001TiN, and for TiN grown at 720°C it changes to (101)STO (001)TiN and [ 01]STO [1 0]TiN (or [ 01]STO [110]TiN). This change of relationship is accompanied by a sharp reduction in the out-of-plane lattice constant of the TiN layer. Fourier transform infrared spectra show that the longitudinal optic modes are active for all the STO films, but the absorption peak associated with the transverse optic mode is observed only in the (101) oriented STO films.     

Cat-CVD-prepared oxygen-rich μc-Si:H for wide-bandgap material

Microcrystalline phase-involved oxygen-rich a-Si:H (hydrogenated amorphous silicon) films have been obtained using catalytic chemical vapor deposition (Cat-CVD) process. Pure SiH₄ (silane), H₂ (hydrogen), and O₂ (oxygen) gases were introduced in the chamber by maintaining a pressure of 0.1 Torr. A tungsten catalyzer was fixed at temperatures of 1750 and 1950 °C for film deposition on glass and crystalline silicon substrates at 200 °C. As revealed from X-ray diffraction spectra, the microcrystalline phase appears for oxygen-rich a-Si:H samples deposited at a catalyzer temperature of 1950 °C. However, this microcrystalline phase tends to disappear for further oxygen incorporation. The oxygen content in the deposited films was corroborated by FTIR analysis revealing SiOSi bonds and typical SiH bonding structures. The optical bandgap of the sample increases from 2.0 to 2.7 eV with oxygen gas flow and oxygen incorporation to the deposited films. In the present thin film deposition conditions, no strong tungsten filament degradation was observed after a number of sample preparations.     

Growth of copper thin films on sputtered-TiN surfaces by metallorganic chemical vapour deposition from (hfac)Cu(I)(VTMS)

Copper (Cu) films were deposited on sputtered TiN with metallorganic chemical vapour deposition (MOCVD) from (hexafluoroacetylacetonate) Cu^(I) (vinyltrimethylsilane) [(hfac)Cu^(I)(VTMS)] at substrate temperatures of 100–300°C, total pressures of 10–2000 mtorr (1–300 Pa) and bubbler temperature of 50°C with Ar carrier gas. Cu was deposited in the form of discontinuous islands up to the film thickness of about 100 nm on the TiN substrate. The orientation of growing films was changed from random orientation to 〈1 1 1〉 with increasing deposition time and temperature. Increasing temperature increased the surface roughness of the film, and grain coalescence. Resistivity was increased due to the carbon incorporation from the thermal decomposition of Cu precursor. This revised version was published online in July 2006 with corrections to the Cover Date.     

Formation of second phase particles in aluminum-copper alloy films

The formation of second phase particles in Al+3% Cu alloy films was examined in order to find differences of the precipitation in thin films from that occurring in bulk alloys. Compared to bulk alloys in the thin film material the formation of Guinier-Preston zones is retarded. In well quenched thin films 60 h at 100°C or 6 h at 130°C are necessary to produce G.P. zones. θ′ particles are nucleated after approximately 100 h at 120°C without formation of θ″. The stable θ-Al₂Cu precipitate was found at temperatures as low as 150°C on the film surface. The results show that excess vacancies cannot be retained in thin films and that the film surfaces provide preferential nucleation sites for the equilibrium precipitate θ-CuAl₂.     

Effect of the carrier gas on the metal-organic chemical vapor deposition of TiN from tetrakis-dimethyl-amido-titanium

The effect of carrier gas such as hydrogen, nitrogen and argon on the deposition rate, film morphology, resistivity and chemical composition of TiN film from tetrakis-dimethyl-amido-titanium (TDMAT) was studied. The deposition rate was higher with argon and nitrogen and lower with hydrogen when the substrate temperature was above 300°C. The surface morphology of the film deposited with hydrogen carrier gas was rough due to the gas phase reaction. The film deposited at the higher substrate temperature with hydrogen had higher resistivity than in the film deposited with argon or nitrogen due to the rough surface.     

Aluminum-induced in situ crystallization of HWCVD a-Si:H films

Aluminum-induced in situ crystallization (AIC) of amorphous silicon films deposited by hot wire chemical vapor deposition (HWCVD) on glass is demonstrated. Aluminum was deposited at temperatures varying from room temperature to 300 °C on HWCVD a-Si:H films. The AIC was observed to take place in situ during the deposition of Al films, when the glass/a-Si:H temperature is kept 300 °C. A 20-nm Al film was effective in inducing crystallization of about 63% in the a-Si:H film. Thus, separate post-deposition annealing step can be avoided. For an Al film thickness comparable to the amorphous silicon film deposited at an optimum deposition rate, crystallization at temperature as low as 200 °C is observed. It was also observed that the growth pattern of c-Si in case of AIC without post-deposition annealing was identical to AIC with annealing step.     

Chemical vapor deposition of copper–cobalt binary films

Chemical vapor co-deposition of Cu–Co films has been demonstrated using (1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)Cu(II) [Cu(hfac)₂] [hfac=hexafluoroacetylacetonate] and (acetylacetonate)Co(II) [Co(acac)₂] [acac=acetylacetonate] as precursors. The deposition was performed at the substrate temperature of 270°C in a warm-wall impinging jet type reactor. The precursor Co(acac)₂ was sublimed at 140°C to achieve reasonable precursor delivery rates and avoid decomposition of precursor in the sublimator. Films with varying Cu content from 17 wt.% to 98 wt.% were deposited by subliming Cu(hfac)₂ in the temperature range of 40–100°C with a fixed Co(acac)₂ delivery rate. The morphologies and crystallinities of the binary films were strongly dependent on the film stoichiometry. Overall, this study provides insights into the mechanism of Cu–Co binary film formation by CVD.     

Morphological changes induced by thermal anneals in NiFe/Ag multilayers; their relation to the resistive and magnetoresistive properties

(Ti, Al)N films have drawn much attention as alternatives for TiN coatings, which are oxidized easily in air above 500 °C. We have investigated the effect of Al content on the oxidation resistance of (Ti_{1 − x}Al_x)N films prepared by r.f. reactive sputtering.

(Ti_{1 − x}Al_xN films (O ≤ x ≤ 0.55) were deposited onto fused quartz substrates by r.f. reactive sputtering. Composite targets with five kinds of Al-to-Ti area ratio were used. The sputtering gas was Ar (purity, 5 N) and N₂ (5 N). The flow rate of Ar and N₂ gas was kept constant at 0.8 and 1.2 sccm, respectively, resulting in a sputtering pressure of 0.4 Pa. The r.f. power was 300 W for all experiments. Substrates were not intentionally heated during deposition. The deposited films (thickness, 300 nm) were annealed in air at 600 900 °C and then subjected to X-ray diffractometer and Auger depth profiling.

The as-deposited (Ti_{1 − x}Al_x)N films had the same crystal structure as TiN (NaCl type). Al atoms seemed to substitute for Ti in lattice sites. The preferential orientation of the films changed with the Al content of the film, x. Oxide layers of the films grew during annealing and became thicker as the annealing temperature increased. The thickness of the oxide layer grown on the film surface decreased with increasing Al content in the film. For high Al content films an Al-rich oxide layer was grown on the surface, which seemed to prevent further oxidation. All of the films, however, were oxidized by 900 °C annealing, even if the Al content was increased up to 0.55.     

Structure and conducting properties of La0.5Sr0.5CoO3−δ films on YSZ

La_0.5Sr_0.5CoO_3−δ (LSCO) thin films were deposited on yttria stabilized zirconia (YSZ) substrates by pulsed laser deposition (PLD) for application to thin film solid oxide fuel cell electrodes. During the deposition, the substrate temperature was varied from 450 to 750°C, and the oxygen pressure in the chamber was varied from 80 to 310 mTorr. Films deposited at 650°C and an oxygen background pressure of 150 mTorr were mostly (100) oriented. Deposition at higher temperatures or under lower oxygen pressures lead to mostly (110) oriented films. Films with low electrical resistivity of 10⁻³ Ω·cm were obtained.     

Effect of annealing temperature on ZnO:Al/p-Si heterojunctions

Al-doped, zinc oxide (ZnO:Al) films with a 1.2 at.% Al concentration were deposited on p-type silicon wafers using a sol-gel dip coating technique to produce a ZnO:Al/p-Si heterojunction. Following deposition and subsequent drying processes, the films were annealed in vacuum at five different temperatures between 550 and 900 °C for 1 h. The resistivity of the films decreased with increasing annealing temperature, and an annealing temperature of 700 °C provided controlled current flow through the ZnO:Al/p-Si heterojunction up to 20 V. The ZnO:Al film deposited on a p-type silicon wafer with 1.2 at.% Al concentration was concluded to have the potential for use in electronic devices as a diode after annealing at 700 °C.     

Sputter deposited nanocrystalline Ni-25Al alloy thin films and Ni/Ni3Al multilayers

Thin films of nominal composition Ni-25at%Al have been sputter deposited from a target of the intermetallic compound Ni₃Al at different substrate deposition temperatures. The film deposited on an unheated substrate exhibited a strongly textured columnar growth morphology and consisted of a mixture of metastable phases. Nanoindentation studies carried out on this film exhibited a strong strain hardening tendency. In contrast, the film deposited at 200 °C exhibited a recrystallized non-textured microstructure consisting of grains of a partially ordered Ni₃Al phase. At higher deposition temperatures (∼400 °C), larger grains of the bulk equilibrium, long-range ordered, Ll₂ Ni₃Al phase were observed in the film. Unlike the film deposited on an unheated substrate, the films deposited at elevated temperatures did not exhibit any dependence of the hardness on the indentation depth and, consequently no strain hardening. The average hardness of the film deposited at 200 °C was higher than the one deposited at 400 °C. In addition to monolithic Ni-25Al thin films, multilayered Ni/Ni3Al thin films were also deposited. Multilayers deposited non-epitaxially on unheated substrates exhibited a strong {111} fiber texture while those deposited epitaxially on (001) NaCl exhibited a {001} texture. Free-standing multilayers of both types of preferred orientations as well as of different layer thicknesses were deformed in tension untill fracture. Interestingly, the {111} oriented multilayers failed primarily by a brittle fracture while the {001} multilayers exhibited features of ductile fracture.     

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.     

Anomalous photovoltaic effect in vacuum-deposited CdTe films

CdTe films of thicknesses varying from 125 to 1250 nm were vapour deposited onto glass substrates at oblique incidence in vacuum at substrate temperatures varying from room temperature to 250 °C. The samples are irradiated with an He-Ne laser from the direction of the deposited layer and through the substrate. It was found that the film thickness and substrate temperature play an important role in changing the magnitude and polarity of the photovoltages generated in CdTe films. A reversal in the polarity of the photovoltage is obtained in certain films depending on the deposition parameters. An attempt is made to interpret the results.     

Preparation of Pt-PtOx thin films as electrode for memory capacitors

Pt-PtO_x thin films were prepared on Si(100) substrates at temperatures from 30 to 700°C by reactive r.f. magnetron sputtering with platinum target. Deposition atmosphere was varied with O₂/Ar flow ratio. The deposited films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. Resistively of the deposited films was measured by d.c. four probe method. The films mainly consisted of amorphous PtO and Pt₃O₄ (or Pt₂O₃) below 400°C, and amorphous Pt was increased in the film as a deposition temperature increased to 600°C. When deposition temperature was thoroughly increased, (111) oriented pure Pt films were formed at 700°C. Compounds included in the films strongly depended on substrate temperature rather than O₂/Ar flow ratio. Electrical resistivity of Pt-PtO_x films was measured to be from the order of 10⁻¹ Ω cm to 10⁻⁵ Ω cm, which was related to the amount of Pt phase included in the deposited films.