Effect Of Fluorine Incorporation Research Articles

Effect of Fluorine Incorporation on DLC Films Deposited by Pulsed Cathodic Arc Deposition on Nitrile Butadiene Rubber and Polyurethane Rubber Substrates

Diamond-like carbon (DLC) and fluorinated diamond-like carbon (F-DLC) films were deposited via pulsed cathodic arc deposition on pretreated nitrile butadiene rubber (NBR) and polyurethane (PU) rubber substrates. Both DLC and F-DLC films showed a more than 50% decrease in coefficients of friction compared to uncoated NBR and PU rubber substrates. The incorporation of fluorine was found to have little influence on the film coefficient of friction. However, a decrease in film wettability was overserved in the F-DLC films compared to the DLC films.

Effects of fluorine incorporation into β-Ga2O3

β-Ga2O3 rectifiers fabricated on lightly doped epitaxial layers on bulk substrates were exposed to CF4 plasmas. This produced a significant decrease in Schottky barrier height relative to unexposed control diodes (0.68 eV compared to 1.22 eV) and degradation in ideality factor (2.95 versus 1.01 for the control diodes). High levels of F (>1022 cm−3) were detected in the near-surface region by Secondary Ion Mass Spectrometry. The diffusion of fluorine into the Ga2O3 was thermally activated with an activation energy of 1.24 eV. Subsequent annealing in the range 350–400 °C brought recovery of the diode characteristics and an increase in barrier height to a value larger than in the unexposed control diodes (1.36 eV). Approximately 70% of the initial F was removed from the Ga2O3 by 400 °C, with the surface outgas rate also being thermally activated with an activation energy of 1.23 eV. Very good fits to the experimental data were obtained by integrating physics of the outdiffusion mechanisms into the Florida Object Oriented Process Simulator code and assuming that the outgas rate from the surface was mediated through fluorine molecule formation. The fluorine molecule forward reaction rate had an activation energy of 1.24 eV, while the reversal rate of this reaction had an activation energy of 0.34 eV. The net carrier density in the drift region of the rectifiers decreased after CF4 exposure and annealing at 400 °C. The data are consistent with a model in which near-surface plasma-induced damage creates degraded Schottky barrier characteristics, but as the samples are annealed, this damage is removed, leaving the compensation effect of Si donors by F− ions. The barrier lowering and then enhancement are due to the interplay between surface defects and the chemical effects of the fluorine.

Effects of Fluorine Doping on the Electrical Performance of ZnON Thin-Film Transistors.

In this work, the effects of fluorine incorporation in high mobility zinc oxynitride (ZnON) semiconductor are studied by both theoretical calculations and experimental evaluation of thin film transistors (TFTs). From density functional theory (DFT) calculations, fluorine acts as a carrier suppressor in the ZnON matrix when it substitutes a nitrogen vacant site (VN). Thin films of ZnON and ZnON:F were grown by reactively cosputtering Zn metal and ZnF2 targets, and their electrical, physical, and chemical characteristics were studied. X-ray photoelectron spectroscopy (XPS) analyses of the nitrogen 1s peaks in ZnON and ZnON:F suggest that as the fluorine incorporation increases, the relative fraction of Zn-N bonds from stoichiometric Zn3N2 increases. On the other hand, the Zn-N bond characteristics arising from nonstoichiometric ZnxNy and N-N bonds decrease, implying that indeed fluorine anions have an effect of passivating the N-related defects. The corresponding TFTs exhibit optimum transfer characteristics and switching ability when approximately 3.5 atomic percent of fluorine is present in the 40 nm thick ZnON:F active layer.

Effects of fluorine incorporation on the structural and electrical properties of Diamond-like carbon

ABSTRACTDiamond-like carbon (DLC) has widespread attention as a new material for its application to thin film solar cells and other semiconducting devices. DLC can be produced at a lower cost than amorphous silicon, which is utilized for solar cells today. However, the electrical properties of DLC are insufficient for this purpose because of many dangling bonds in DLC. To solve this problem, we investigated the effects of the fluorine incorporation on the structural and electrical properties of DLC.We prepared five kinds of fluorinated DLC (F-DLC) thin film with different amounts of fluorine. Films were deposited by the radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD) method. C6H6 and C6HF5 were used as source gases. The total gas flow rate was constant and the gas flow rate ratio R (=C6H6 / (C6H6 + C6HF5)) was changed from 0 to 1 in 0.25 ratio steps. We also prepared nitrogen doped DLC (F-DLC) on p-Si using N2 gas as a doping gas to form nitrogen doped DLC (F-DLC) / p-Si heterojunction diodes.X-ray photoelectron spectroscopy (XPS) showed that fluorine concentration in the DLC films was controlled. Moreover, the XPS analysis of the C1s spectrum at R=2/4 showed the presence of CF bonding. At R=1, CF2 bonding was observed in addition to CF bonding. The sheet resistivity of the films changed from 3.07×1012 to 4.86×109 Ω. The minimum value was obtained at R=2/4. The current-voltage characteristics indicated that nitrogen doped F-DLC of 2/4 and p-Si heterojunction diode exhibited the best rectification characteristics and its energy conversion efficiency had been maximized. This is because of a decrease of dangling bonds density by ESR analysis and an increase of sp2 structures by Raman analysis. When the fluorine is over certain content, the sheet resistivity increases because chain structures become larger, which is due to the CF2 bonding in F-DLC prevents ring structures. Many C2F4 species were observed and it may become precursors of the chain structure domains, such as (CF2)n.In this study, we revealed effects of fluorine incorporation on DLC and succeeded in increasing its conductivity and improving rectification characteristics of DLC/ p-Si hetero-junction diodes. Our results indicate that DLC fluorination is effective for the semiconducting material, such as solar cell applications.

Removal of Interfacial Layer in HfO<sub>2</sub> Gate Stack by Post-Gate Cleaning Using NF<sub>3</sub>/NH<sub>3</sub> Dry Cleaning Technique

HfO2 gate stack has been one of the most popular subjects of research in recent years due to its outstanding material properties, such as high-k (20~25), wide band gap (~5.68eV), and the compatibility with Si-based semiconductor process technology. However, the interfacial layer (IL) with a reduced k-value between HfO2 dielectric and Si channel is still a critical issue for future ultra large scale integration (ULSI) technology application of the HfO2 gate stack. Various ways have been studied to improve the IL properties of HfO2 gate stack and to achieve ~1nm-thick equivalent oxide thickness (EOT) of the gate stack. Recently, fluorine incorporations into the HfO2 gate stack have been suggested for improvement of the electrical properties of the gate stack by defect passivation.1,2 However, it was reported that the SiOx IL grows during the fluorine treatment of HfO2 film, which finally led to degradation of electrical characteristics.2 In this paper, we present interesting findings on the IL removal effect of fluorine incorporation into the HfO2 gate stack where a post-gate dry cleaning technique is used with the NF3/NH3 plasma.

Improved Characteristics of InGaZnO Thin-Film Transistor by Using Fluorine Implant

The effects of fluorine incorporation in amorphous InGaZnO by ion implant on the characteristics of InGaZnO thin-film transistor have been investigated. The electrical characteristics of thin-film transistor can be improved by this treatment due to increase of carrier concentration and passivation of defects in InGaZnO. Consequently, the saturation carrier mobility can be increased from 25.2 cm2/V·s to a high value of 34.0 cm2/V·s, and the output current can be nearly doubled. However, device degradation is observed for very high fluorine dose above 1.0 × 1015 /cm2, possibly ascribed to excessive interstitial fluorine atoms and too many fluorine-induced electrons in InGaZnO.

Electrical properties improvement of high-k HfO2 films by combination of C4F8 dual-frequency capacitively coupled plasmas treatment with thermal annealing

Abstract The effect of fluorine incorporation on the electrical properties of HfO 2 gate oxide were investigated, especially on the frequency dispersion, hysteresis and the density of interface states. By treating HfO 2 films using octafluorocyclobutane (C 4 F 8 ) 60 MHz/2 MHz dual-frequency capacitively coupled plasmas, fluorine atoms were incorporated into the HfO 2 films, but thinner C:F films also deposited on the surface of the HfO 2 films. After a following thermal annealing, the C:F films were removed, accompanied the formation of the C C group and Hf F bonds. By optimizing the low frequency (LF) power, the appropriate fluorine incorporation significantly improved the quality of the gate oxide, resulting in excellent electrical properties. At the LF power of 30 W, the smallest Δ V fb , hysteresis and the lowest interface state density were obtained. These improvements were attributed to the passivation of oxygen vacancies and the reduction of defects states density in the gap by forming Hf F bonds.

Effects of fluorine incorporation on the microstructure and optical properties of ZnO thin films synthesized by Sol-gel technique

Fluorine doped Zinc oxide (ZnO) [FZO] transparent conducting thin films were deposited by sol-gel spin coating method. Zinc acetate and amonium fluoride were used as precursor solution materials. Microstructural, morphologycal, and optical properties of the films were investigated as a function of flourine (F) doping ranging from 0 to 3.5% mole. From x-ray diffraction (XRD) patterns the films exhibited a hexagonal wurtzite structure with preferred c-axis orientation. All the films had a highly preferential c-axis orientation and exhibited (002) preferential growth in all the dopant ratios. Grain sizes of the films were varied in range of 15 to 18 nm. TheSEM images of the films showed well crystallinity with good homogeneity, smooth surface and uniform grains. The average optical transmittance in the entire visible wavelength region was higher than 95% for all F-doped ZnO except undoped ZnO thin film. The band gap energy values were determined as 3.270, 3.291, 3.293 and 3,287 eV, respectively for undoped ZnO, 0.5, 1.5 and 3.5% mole FZO samples. The band gap values increased with increasing the F dopant concentration for all doped samples. These results make FZO thin films an attractive candidate for transparent material applications. Key words: Flourine doped Zinc oxide (ZnO), Sol-gel growth, transparent conducting oxide (TCO), thin films, microstructures.

Structural properties of porous silicon/SnO2:F heterostructures

In this work we present structural studies made on SnO2 deposited on macroporous silicon structures. The porous silicon substrates were prepared by anodization of p-type silicon wafers. The SnO2 doped layers were synthesized by the sol–gel method from SnCl4·5H2O-ethanolic precursor, where the effect of fluorine doping level on structural properties was investigated. The fundamental structural parameters of tin oxide such as the lattice parameter and the crystallite size were studied in correlation with the dopant concentration. In addition, the effect of fluorine incorporation into the structure of tin oxide was analyzed on the basis of theoretical calculations that take into account the structural factor. The results obtained indicate that incorporation of fluorine occurs only at substitutional sites for SnO2 deposited on porous silicon.

Effect of fluorine incorporation on long-term stability of magnesium-containing hydroxyapatite coatings

Dissolution resistance and adhesion strength are two main concerns for long-term stability of surface coated metal implants. In this study, fluorine ions are incorporated into magnesium-containing hydroxyapatite coatings (MgF(y)HA) via sol-gel method to improve the long-term stability of the implants. Surface and interface are studied in terms of phases, depth profiling and chemical bonds by grazing incidence X-ray diffraction, glow discharge optical emission spectroscopy and X-ray photoelectron spectroscopy. The long-term stability is evaluated by dissolution and pull-off test. The results show that fluorine promotes the incorporation of magnesium in HA lattice. The elemental interdiffusion and chemical bonding take place at the coating/substrate interface. Both the dissolution resistance and the adhesion strength are enhanced by fluorine incorporation, thus the long-term stability of the implant is improved.

Effects of fluorine incorporation into HfO2 gate dielectrics on InP and In0.53Ga0.47As metal-oxide-semiconductor field-effect-transistors

In this work, the effects of fluorine (F) incorporation on electrical characteristics of HfO2/InP and HfO2/In0.53Ga0.47As gate stack are presented. F had been introduced into HfO2 gate dielectric by postgate CF4 plasma treatment, which was confirmed by x-ray photoelectron spectroscopy analysis and a secondary ion mass spectrometry technique. Compared to the control sample, fluorinated samples had great improvements in subthreshold swing, hysteresis, the normalized extrinsic transconductance, and the normalized drain current. These improvements can be attributed to the reduction in fixed charge in the HfO2 bulk and less interface trap density at the HfO2/III–V interface.

Effects of fluorine incorporation on the properties of Ge p -MOS capacitors with HfTiON dielectric

In this work, Ge p-MOS capacitors with HfTiON gate dielectric were fabricated by sputtering method. Pre-deposition fluorine plasma treatment and post-deposition fluorine plasma annealing were used to improve the electrical and reliability properties of Ge p-MOS capacitors. Experimental results showed that both methods could improve the interface quality with lower interface-state density, less frequency dispersion, and also enhance the reliability properties with smaller increases of oxide charge and gate leakage after high-field stressing. Compared with pre-deposition fluorine-plasma treatment, post-deposition fluorine plasma annealing achieved higher quality of high- k/Ge interface such as lower interface-state density, higher dielectric constant and lower stress-induced gate leakage current. By XPS and AFM analyses, the improvements should be due to the passivation effects of fluorine on oxygen vacancies, dangling bonds and the dielectric surface.

Effects of fluorine incorporation and forming gas annealing on high-k gated germanium metal-oxide-semiconductor with GeO2 surface passivation

Effective pregate surface passivation and postgate treatments are very important to optimize the germanium metal-oxide-semiconductor (MOS) interface quality. In this work, pregate GeO2 surface passivation and postgate treatments including CF4-plasma treatment and forming gas annealing are employed to make high quality HfO2 gated germanium MOS capacitors. Excellent electrical characteristics with negligible capacitance-voltage stretch-out and frequency dispersion are achieved. The interface trap density of TaN∕HfO2∕GeOx∕Ge MOS structure is as low as 2.02×1011cm−2eV−1 at the minimum. Comparing to the forming gas annealing, it is found that CF4-plasma treatment is more effective to passivate interface states located in the upper half of Ge bandgap.

Physical properties of transparent and conducting sprayed fluorine doped zinc oxide thin films

Transparent and conductive thin films of fluorine doped zinc oxide (FZO) were deposited onto the corning glass substrates by a spray pyrolysis technique using aqueous solutions of zinc acetate and ammonium fluoride as precursors. The effect of fluorine incorporation on structural, electrical, and optical properties of as-deposited and annealed (473 K for 2 h) films was studied. The X-ray diffraction studies indicate the polycrystalline hexagonal (wurtzite) crystal structure of the film. The FZO films were oriented along (002) plane parallel to the substrate. The crystallite size determined using a Scherrer's formula was in the range of 43–94 nm. SEM and AFM images of FZO films show uniformly distributed spherical grains of varying sizes. Films were uniform, pinhole-free, with 80–90 % transmittance in the visible region at 550 nm. The addition of fluorine induces a decrease in the electrical resistivity of FZO films upto 15 at% F doping. The lowest resistivity (∼10 −4 Ω cm) was observed for the annealed film deposited at 15 at% fluorine doping thereby resulting in the highest figure of merit achieved till date (7 × 10 −2□ Ω −1).

Fluorine incorporation at HfO2∕SiO2 interfaces in high-k metal-oxide-semiconductor gate stacks: Local electronic structure

Effects of fluorine incorporation on the electrical properties of HfO2∕SiO2 dielectric stacks are investigated through both ab initio simulations and electrical measurements. The results show that F ions are able to remove midgap states resulting from undercoordinated Hf ions at the HfO2∕SiO2 interface. They also indicate that F incorporation increases the leakage current if an excessive amount of F ions are present in the dielectric, beyond that required to passivate the undercoordinated interfacial Hf ions. A possible way to maximize the benefits of F incorporation for high-k gate stack electrical characteristics is discussed.

Effect of fluorine incorporation on silicon dioxide prepared by high density plasma chemical vapor deposition with SiH4∕O2∕NF3 chemistry

The effect of fluorine incorporation on properties of silicon dioxide thin films has been studied as a function of NF3∕O2 gas flow ratio. Fluorine was incorporated into silicon dioxide films during high density plasma chemical vapor deposition with the SiH4∕O2∕NF3∕He gas mixture used to improve the gap-filling ability for shallow trench isolation of devices. Refractive index measured by ellipsometry decreased with increasing NF3∕O2 flow ratios for both as-deposited and annealed films. X-ray reflectivity measurements showed that both fluorine incorporation and thermal annealing reduced the film density. The analysis of infrared absorption spectra showed the relaxation of the Si-O-Si bond with increasing NF3∕O2 flow ratios and thermal annealing. The secondary ion mass spectroscopy and x-ray photoelectron spectroscopy studies confirmed the behavior of fluorine diffusion and the binding energy for each species in the films, respectively. These results showed that through fluorine incorporation and thermal annealing, the network structures of silicon dioxide could be modified from low order rings to high order rings accompanied by the enlargement of nanovoids.

Improvement of charge-to-breakdown distribution by fluorine incorporation into thin gate oxides

This paper reports on the effect of fluorine incorporation on gate-oxide reliability, especially the spatial distribution of charge-to-breakdown (Q/sub BD/). Fluorine atoms were implanted into gate electrodes and introduced into gate-oxide films by annealing. Excess fluorine incorporation increased the oxide thickness and degraded not only the reliability of Si/SiO/sub 2/ interfaces but also dielectric-breakdown immunity. However, it was found, for the first time, that appropriate fluorine incorporation into gate-oxide films could dramatically improve Q/sub BD/-distribution tails in Weibull plots, while maintaining both Si/SiO/sub 2/ interface characteristics and average Q/sub BD/ values. The experimental result for a depth profile of fluorine atoms indicated that fluorine atoms are located dominantly at the two interfaces of the gate-oxide film. In addition, the results of infrared (IR) absorption analysis indicated that the strain of SiO/sub 2/ structures is reduced with increasing fluorine doses. We proposed that both strain release and restructuring of the SiO/sub 2/ network by fluorine incorporation are responsible for improving the Q/sub BD/ of weaker oxide films.

Analysis of the role of fluorine content on the thermal stability of a-C:H:F thin films

The effect of fluorine incorporation on the thermal stability of hydrogenated amorphous carbon (a-C:H) films was investigated by Raman spectroscopy, infrared (IR) absorption, X-ray photoelectron spectroscopy (XPS), as well as measurements of the film thickness. Results of IR and XPS analysis suggest that the total fluorine content after annealing corresponds to the amount of fluorine bonded to carbon in the as-deposited films. The evolution of Raman spectra obtained on films before annealing indicates that progressive fluorine incorporation is accompanied by graphitisation. In particular, the decrease in the optical bandgap is interpreted as a clustering of the existing sp2 carbon sites. Under thermal annealing, the film structures are very stable and the films do not show any change in refractive index values with respect to the original as-deposited films, for all fluorine contents. This behaviour is most likely due to extended graphitisation, with no sp2 clustering. The experimental findings suggest that the strength of the CF bonding configuration promotes thermal stability of the films.

Synthesis and self‐assembly of fluorinated block copolymers

AbstractFluorinated block copolymers combine the unique properties of fluoropolymers and the intriguing self‐assembly of hybrid macromolecules. The preparation of the title molecules by selective fluorination procedures and the effect of fluorine incorporation on the material thermodynamics are presented. We highlight two fluorination schemes developed in our laboratory, difluorocarbene and perfluoroalkyliodide additions to polydienes, that allow for the selective and tunable incorporation of different fluorinated groups into model block copolymers. The fluorination changes the physical properties of the parent materials and leads to interesting changes in the component incompatibilities. The role of fluorination in determining block copolymer thermodynamics in both the solid state and in solution and in ultimately exploiting fluorination to produce novel, higher order structures is central to our research efforts. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 1–8, 2002

Relationship between the optical and mechanical properties of fluorinated amorphous carbon thin films

Fluorinated amorphous carbon (a-C:H:F) thin films were grown from CH 4/CF 4/Ar gas mixtures using a 13.56 MHz radiofrequency (RF) plasma source. The effect of fluorine incorporation on the mechanical properties of the films was investigated by depth sensing indentation, while Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray reflectivity (XRR) and ellipsometry measurements were exploited to study their vibrational, structural and optical properties. While raising fluorine content in the film, visible Raman results show that the sp 2 carbon sites undergo a gradual ordering into graphitic clusters, which are responsible for a higher optical absorption. Nanoindentation measurements showed decreased elasticity of the film, as well as decreased hardness upon fluorine incorporation. A clear correlation between the mechanical properties and the optical constants was found as a function of fluorine content in the film.