Multi-solvent ellipsometric porosimetry analysis of plasma-treated porous SiOCH films

Porous ultra low-k (ULK) dielectrics are used to reduce resistance-capacitance delay for advanced complementary metal oxide semiconductor interconnects. Since the porosity leads to an increased sensitivity of the material to plasma processes (etching and post-etching plasmas), dedicated characterization techniques are needed to assess the ULK properties during its integration. This study shows that ellipsometric porosimetry, employed with an appropriate multi-solvent protocol, can be effectively used to characterize different plasma-treated porous SiOCH (p-SiOCH) films in terms of porosity, pore sealing and hydrophobicity. It was found that after exposure to fluorocarbon, NH₃, H₂, CH₄ or O₂ based plasmas the p-SiOCH surface is modified leading to moisture uptake. According to the plasma, the solvent adsorption is also modified due to a densification of the surface. In that case solvent adsorption measurements were performed in a kinetic mode to quantify the plasma-sealing effect.     

Thin film passivation of organic light emitting diodes by inductively coupled plasma chemical vapor deposition

The characteristics of an SiN_x passivation layer grown by a specially designed inductively coupled plasma chemical vapor deposition (ICP-CVD) system with straight antennas for the top-emitting organic light emitting diodes (TOLEDs) are investigated. Using a high-density plasma on the order of ∼ 10¹¹ electrons/cm³ formed by nine straight antennas connected in parallel, a high-density SiN_x passivation layer was deposited on a transparent Mg-Ag cathode at a substrate temperature of 40 °C. Even at a low substrate temperature, single SiN_x passivation layer prepared by ICP-CVD showed a low water vapor transmission rate of 5 × 10^− 2 g/m²/day and a transparency of ∼ 85% respectively. In addition, current-voltage-luminescence results of the TOLED passivated by the SiN_x layer indicated that the electrical and optical properties of the TOLED were not affected by the high-density plasma during the SiN_x deposition process.     

Thermal stability of advanced gate stacks consisting of a Ru electrode and Hf-based gate dielectrics for CMOS technology

Metallic Ru and Hf-based dielectrics such as HfO₂, HfSiO_x and HfSiON, are promising materials for the gate electrode and gate dielectrics, respectively. This paper reports on the thermal stability of gate stack systems comprised of Ru/Hf-based dielectrics. Layers of both types of material were prepared on Si substrate by metal-organic chemical vapour deposition (MOCVD). The stacks underwent exposure by rapid thermal annealing (RTA) in pure nitrogen ambience at temperatures 800, 900, and 1000 °C for 10 s. The samples were analysed using Rutherford backscattering spectrometry (RBS). Small changes were found in the stacks treated at 800 and 900 °C. The most stable stack was found to be one with a HfSiON dielectric layer, which was resistant also at temperature 900 °C. However, the annealing at 1000 °C induced massive diffusion at both interfaces for all types of stack. The results imply a limited thermal stability of the Ru/Hf-based dielectric gate stacks during the source/drain activation step.     

CF4 plasma effect combined with rapid thermal annealing for high-k Er2O3 dielectrics

In this study, the influence of the duration of CF₄ plasma treatment of rapid thermal annealing on high-k Er₂O₃ dielectrics deposited on polycrystalline silicon was investigated using electrical and material analyses. Results demonstrate that Er₂O₃ dielectric films annealed at 800 °C and plasma treated with CF₄ for a period of 1 min exhibited excellent dielectric performance, including a higher breakdown electric field, lower charge trapping rate, and a larger charge-to-breakdown than the as-deposited sample. Performance improvements were caused by the incorporation of fluorine atoms and the reduction of dangling bonds and defect traps.     

Thermal effects and plasma damage upon encapsulation of polymer solar cells

A barrier structure consisting of silicon oxide and silicon nitride films was deposited via plasma-enhanced chemical vapor deposition (PECVD) for the encapsulation of polymer solar cells (PSCs). The total concentration of the solution and the ratio of P3HT and PCBM on the performance of polymer solar cells were studied by UV-Vis absorption spectroscopy, atomic force microscopy and photocurrent measurement. Base on these measurements, there is a compromise between light absorption and phase separation with increasing blend concentration. The PSCs were annealed at 80, 100, 120 and 140 °C for 10-60 min to investigate the thermal effects and to estimate the best deposition temperature of the barrier layers. Nevertheless, the devices with the encapsulation of barrier layers had relatively low power conversion efficiencies (PCE) of 0.98% comparing to the devices heated in the PECVD system (1.57%) at the same condition of 80 °C for 45 min due to the plasma damage during the film deposition process. After inserting a 5-nm TiO_x layer between Al/barrier structure and active layer against the plasma damage, the annealed devices presented an average PCE of 2.26% and demonstrated over 50% of their initial value after constant exposure to ambient atmosphere and sunlight for 1500 h.     

The effect of nitrogen on the properties of zinc nitride thin films and their conversion into p-ZnO:N films

Zinc nitride thin films were deposited by magnetron sputtering using ZnN target in plasma containing either N₂ or Ar gases. The rf-power was 100 W and the pressure was 5 mTorr. The properties of the films were examined with thermal treatments up to 550 °C in N₂ and O₂ environments. Films deposited in Ar plasma were opaque and conductive (ρ ∼ 10^− 1 to 10^− 2 Ω cm, N_D ∼ 10¹⁸ to 10²⁰ cm^− 3) due to excess of Zn in the structure. After annealing at 400 °C, the films became more stoichiometric, Zn₃N₂, and transparent, but further annealing up to 550 °C deteriorated the electrical properties. Films deposited in N₂ plasma were transparent but very resistive even after annealing. Both types of films were converted into p-type ZnO upon oxidation at 400 °C. All thermally treated zinc nitride films exhibited a shoulder in transmittance at around 345 nm which was more profound for the Ar-deposited films and particularly for the oxidized films. Zinc nitride has been found to be a wide band gap material which makes it a potential candidate for transparent optoelectronic devices.     

Effect of CuO addition to Nd(Zn1/2Ti1/2)O3 ceramics on sintering behavior and microwave dielectric properties

The microwave dielectric properties and microstructures of CuO-doped Nd(Zn_1/2Ti_1/2)O₃ ceramics prepared by the conventional solid-state route were investigated. The prepared Nd(Zn_1/2Ti_1/2)O₃ exhibits a mixture of Zn and Ti showing 1:1 order in the B-site. As an appropriate sintering aid, not only did CuO lower the sintering temperature, it could effectively hold back the evaporation of Zn in the Nd(Zn_1/2Ti_1/2)O₃. Moreover, CuO only resided in boundaries, which was confirmed by EDX analysis. The measured lattice parameters of CuO-doped Nd(Zn_1/2Ti_1/2)O₃ (a = 5.4652 ± 0.0005 ?, b = 5.6399 ± 0.0007 ?, c = 7.7797 ± 0.0008 ? and β = 90.01 ± 0.01°) retained identical to that of the pure Nd(Zn_1/2Ti_1/2)O₃ in all cases. In comparison with the pure Nd(Zn_1/2Ti_1/2)O₃ ceramics, specimen with 1 wt.% CuO addition possesses a compatible combination of dielectric properties with a ε_r of 30.68, a Q × f of 158,000 GHz (at 8 GHz) and a τ_f of − 45 ppm/°C at 1270 °C. It also indicated a 60 °C lowering in the sintering temperature. The proposed dielectrics can be a very promising candidate material for microwave or millimeter wave applications requiring extremely low dielectric loss.     

Deposition of silicon nitride thin films by hot-wire CVD at 100 °C and 250 °C

Silicon nitride thin films for use as passivation layers in solar cells and organic electronics or as gate dielectrics in thin-film transistors were deposited by the Hot-wire chemical vapor deposition technique at a high deposition rate (1-3 ?/s) and at low substrate temperature. Films were deposited using NH₃/SiH₄ flow rate ratios between 1 and 70 and substrate temperatures of 100 °C and 250 °C. For NH₃/SiH₄ ratios between 40 and 70, highly transparent (T ~ 90%), dense films (2.56-2.74 g/cm³) with good dielectric properties and refractive index between 1.93 and 2.08 were deposited on glass substrates. Etch rates in BHF of 2.7 ?/s and < 0.5 ?/s were obtained for films deposited at 100 °C and 250 °C, respectively. Films deposited at both substrate temperatures showed electrical conductivity ~ 10^− 14 Ω^− 1 cm^− 1 and breakdown fields > 10 MV cm^− 1.     

Effect of microwave remote plasma and radiofrequency plasma on the photoluminescence of (0001) epitaxial ZnO films

Photoluminescence of (0001) epitaxial ZnO films with thicknesses of 10, 30 and 100 nm on C-sapphire substrates have been studied at room temperature and after exposure to Ar, Ar–O₂, Ar–N₂ and Ar–H by remote microwave and radiofrequency plasmas. The photoluminescence are not modified by remote plasma treatments where only neutral species were involved. On the contrary, the photoluminescence signal is enhanced or quenched after radiofrequency plasma treatments when energetic ion species are involved in the surface treatment processes. Little changes of electric properties are observed, however, the optical transmission indicates that the absorption edge and probably also the index of refraction are affected. Photoluminescence peak shifts, widths and intensities changes show very strong similarities with polarized emission of ZnO single crystal where it exists a strong dichroism. The photoluminescence emission properties may then result from this optical modification. However, the plasma treatments on the different samples show very low stability in time, except, for the treatment in argon plasma alone. In this later case, in-situ monitoring of photoluminescence as a function of temperature revealed a partial recovery of the photoluminescence properties after a heat treatment at 400 °C for few minutes. These results indicate that photoluminescence of (0001) ZnO thin film, related to σ-emission polarized emission from c-axis polar surfaces, is highly affected by surface and implanted charged species.     

Synthesis and electroluminescent property of tris{2-(naphtha [3,4]imidazol-2-yl) pyridinato} Aluminum

An emission material, tris{2-(naphtha [3,4]imidazol-2-yl) pyridinato} Aluminum (AlNIP) used for organic light emitting devices, has been synthesized. The decomposition temperature was observed at 510 °C and no melting transition (T_m) of AlNIP was observed up to 400 °C. The emission spectrum of organic emitting device using AlNIP as emitted layer exhibits a broad maximum at 536 nm. The color of the emitted light is in the orange region in the CIE coordinate of x = 0.41 y = 0.53.     

Properties of screen-printed Ho-Ba-Cu-O films on YSZ substrates

High-T_c screen-printed Ho-Ba-Cu-O films were prepared on YSZ substrates by a melt processing method. The films were fired at T_s = 1000-1050 °C for 5 min and cooled to 450 °C by two steps in flowing O₂. The maximum critical current density J_c (77 K, 0 T) of 2.0 × 10³ A cm^− 2 was only attained under much limited firing conditions; T_s = 1020 °C and cooled to 800 °C at a cooling rate of 400 °C h^− 1.     

Electrical characterization of high-k gate dielectrics on Ge with HfGeN and GeO2 interlayers

Two kinds of HfSiO_x/interlayers (ILs)/Ge gate stack structures with HfGeN- and GeO₂-ILs were fabricated using electron cyclotron resonance (ECR) plasma sputtering and the subsequent post deposition annealing (PDA). It was found that HfGe was formed by the deposition of Hf metal on Ge and changed to HfGeN by N₂ ECR-plasma irradiation, which was used as IL. Another IL was GeO₂, which was grown by thermal oxidation at 500 °C. For dielectrics with HfGeN-IL, PDA of 550 °C resulted in effective oxide thickness (EOT) of 2.2 nm, hysteresis of 0.1 V, and interface state density (D_it) = 7 × 10¹² cm^− 2 eV^− 1. For dielectrics with GeO₂-IL, PDA of 500 °C resulted in EOT of 2.8 nm, hysteresis of 0.1 V, and D_it = 1 × 10¹² cm^− 2 eV^− 1. The structural change of HfSiO_x/GeO₂/Ge during the PDA was clarified by using X-ray photoelectron spectroscopy, and the gate stack formation for obtaining the good IL was discussed.     

Investigation of SiOxCy film as the encapsulation layer for full transparent OLED using hollow cathode discharge plasma at room temperature

The plasma polymer of SiO_xC_y film has attracted much attention because it could possess both the organic and inorganic properties simultaneously for wide range applications. In this work, a SiO_xC_y film with a gradient composition through tuning the N₂O/N₂O + Ar ratio from 0% to 100% was used for TOLED encapsulation using hollow cathode discharge plasma. In order to confirm whether the plasma damage was caused during the PECVD process, a ZnO buffer layer prepared using RF sputtering was deposited before encapsulation. Furthermore, the reference samples with glass lid encapsulation were also used for comparison. The results showed that the SiO_xC_y film with a gradient composition cooperated with the sputtering ZnO buffer layer was a simple and effective method for TOLED encapsulation.     

Initial stages of metal-organic chemical-vapor deposition of ZrO2 on a FeCrAl alloy

The initial stages of metal-organic chemical-vapor deposition of ZrO₂ on a model FeCrAl alloy was investigated using synchrotron radiation photoelectron spectroscopy, X-ray absorption spectroscopy, scanning Auger microprobe, and time of flight secondary mass spectrometry. The coatings were grown in ultra-high vacuum at 400 °C and 800 °C using the single source precursor zirconium tetra-tert-butoxide. At 400 °C the coatings mainly consist of tetragonal ZrO₂ and at 800 °C a mixed ZrO₂/Al₂O₃ layer is formed. The Al metal diffuses from the FeCrAl bulk to the metal/coating interface at 400 °C and to the surface of the coating at 800 °C. The result indicates that the reaction mechanism of the growth process is different at the two investigated temperatures.     

Realization of high mobility p-type co-doped ZnO: AlN film with a high density of nitrogen-radicals

High mobility p-type ZnO:AlN thin films have been efficiently realized by utilizing pre-activated nitrogen (N) plasma sources with an inductively coupled dual target co-sputtering system. High density of N-plasma-radicals was generated with an additional RF power applied through a ring-shaped quartz-tube located inside the chamber during co-sputtering process. The AlN codoped ZnO film shows excellent p-type behavior with a high mobility and a hole concentration of 154 cm^2°V^− 1s^− 1 and about 3 × 10^18°cm^− 3 at 600 °C, respectively. Electrical properties of p-n homo-junction devices based on p-type ZnO film are also discussed.     

In-situ production of Fe-TiC composite

A TiC/Fe composite was produced by a novel process which combines in situ with powder metallurgy techniques. The microstructure of the Fe-TiC composite was studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD); with the help of differential thermal analysis (DTA), the reaction path of the Fe-Ti-C system was discussed. The results show that the production of an iron matrix composite reinforced by TiC particulates using the novel process is feasible. TiC particles exhibit homogeneous distribution in the α-Fe matrix. The reaction path is as follows: first, allotropic change Fe_α → Fe_γ at 765.6 °C; second, formation of the compound Fe₂Ti at 1078.4 °C because of the eutectic reaction between Ti and Fe; third, reaction between carbon and melted Fe₂Ti causing formation of TiC at 1138.2 °C; finally, Fe₃C formation due to the eutectic reaction between remanent C and Fe at 1146.4 °C.     

Effect of high temperature post-oxidizing on tribological and corrosion behavior of plasma nitrided AISI 316 austenitic stainless steel

In this research, the microstructure, tribological and corrosion properties of plasma nitrided-oxidized AISI 316 austenitic stainless steel at high oxidation temperature were studied and compared with conventional plasma nitride. The structural, tribological and corrosion properties were analyzed using XRD, SEM, microhardness testing, pin-on-disk tribotesting and electrochemical polarization. Plasma nitriding was conducted for 5 h at 450 °C with gas mixture of N₂/H₂ = 1/3 to produce the S-phase. The nitrided samples were post-oxidized at 500 °C with gas mixture of O₂/H₂ = 1/5 for 15, 30 and 60 min. X-ray diffraction confirmed the development of CrN, ? and γ′ nitride phases and magnetite (Fe₃O₄) oxide phase under plasma nitriding-oxidizing process. In addition, it was found that oxidation treatment after plasma nitriding provides an important improvement in the friction coefficient and the corrosion resistance. The optimized wear and corrosion resistance of post-oxidized samples were obtained after 15 min of oxidation.     

Lithium cobalt oxide thin films deposited at low temperature by ionized magnetron sputtering

Thin films of lithium cobalt oxides have been deposited by ionized magnetron sputter deposition with and without substrate heating. The technique uses a built-in radio frequency coil to generate an inductively coupled plasma (ICP) confined close to the substrate. The ICP plasma results in ion bombardment on the film surface, which serves as an extra energy input during film growth. Therefore, the film properties can be modified at a relatively lower temperature. The plasma irradiation induces variations of crystallography and morphology, as characterized by X-ray diffraction and scanning electron microscopy. The deposited films were tested as cathodes for lithium batteries, and the discharge curves were measured to compare the electrochemical properties of the deposited films. Applying suitable plasma irradiation, well crystallized LiCoO₂ phase was obtained at 350 °C (substrate temperature), which was much lower than the temperature (700 °C-750 °C) for conventional post anneal process. The LiCoO₂ films, fabricated under in-situ plasma irradiation and a relatively lower substrate temperature (350 °C), showed a discharge potential plateau at 4.3 V-3.8 V with a capacity of ∼ 110 mAh/g as discharged to 1.5 V.     

Plasma surface interaction in PACVD and PVD systems during TiAlBN nanocomposite hard thin films deposition

In a PACVD system, titanium alloys were exposed to inductive radio-frequency (RF) plasmas of H₂ + N₂ and Ar + BCl₃+H₂ + N₂ gas mixtures for their nitriding and boron nitride respectively. Hard nanocomposite thin films of TiAlN and TiAlBN were formed on Ti-6Al-4V alloys in an inductive RF plasma of Ar + H₂ + N₂ and Ar + 3.5 vol.% of BCl₃ + H₂ + N₂, respectively. The substrates were grounded, i.e., self-biased, during plasma thin film formation for 30 min each. TiAlBN was deposited by sputtering in a reactive PVD system. A quadrupole mass spectrometer (QMS) sampled the plasma at a constant distance of 0.5 cm from the sample surface in real time. The mass species (m/e) at 0.5 cm were recorded during the deposition process. To separate the particles reaching the substrate surface from those leaving it, the nanocomposite thin films coated samples of Ti alloys were introduced in an RF plasma of Ar + H₂ mixture without the presence of N₂ and BCl₃ and negatively biased up to V_b = − 350 V. The QMS at 0.5 cm measures the etched and sputtered species from the surface of the coated samples. Comparing the QMS results between the grounded samples with the monomers in the RF plasma and the negatively biased voltage samples without monomers in the Ar + H₂ plasma the net plasma surface interactions (PSI) were evaluated. The behavior of the coating process of nanocomposite thin films of TiAlN and TiAlBN on the Ti alloy samples is strongly dependent on the plasma surface phenomena.     

Room-temperature crystallization of amorphous films by RF plasma treatment

The crystallization of amorphous thin films was achieved by 13.56 MHz RF (radio frequency) plasma treatment. This crystallization process has a strong advantage that the sample temperature is lower than 120 °C during the plasma treatment even without compulsory cooling and various amorphous films are crystallized after 2 min or so. This treatment works on amorphous films of various materials, independently of the film preparation method and substrate materials. Crystallization has been confirmed on amorphous thin films of sputtered ITO (tin doped indium oxide) deposited on soda-lime glass and PET (polyethylene terephthalate), of sputtered TiO₂ on soda-lime glass, of sol-gel derived TiO₂ on silicon wafer and of sputtered hydrogen-doped silicon on soda-lime glass.The plasma gas pressure was found to be the key parameter in the plasma crystallization process. The appropriate gas pressure depends on the plasma gas species and not on film or substrate materials. A Cu electrode, attached to the backside of the substrate and is electrically floated from the electric ground, was found to enhance the plasma crystallization performance.