Influence of moisture on BCN (low-K) film for interconnection reliability

The integration of low dielectric constant (low-K) interlayers and Cu wiring is necessary to produce next-generation LSI devices. Low-K films of porous type have been investigated to reduce a dielectric constant (K value). However, most porous low-K materials have faced a serious problem of water incorporation during the wet processes used in making the interconnections. Thus, the influence of moisture on boron carbon nitride (BCN) films is important to investigate. To study water-treated BCN films, we measured the current-versus-voltage (I–V) and capacitance-versus-voltage (C–V) characteristics of BCN films, using an MIS (mercury electrode/BCN/Si substrate) structure. We found that both the leakage current and dielectric constant of BCN films decrease as the film's carbon-composition ratio increases. D₂O detection using thermal desorption spectroscopy (TDS) reveals that BCN films with carbon-composition ratios greater than 30% can suppress the incorporation of water into the film. Desorption of hygroscopic water from the BCN film occurred at temperatures as low as 390 °C, which is a normal LSI-production process temperature. The use of BCN film appears to resolve the serious problem of water incorporation into the porous low-K materials. In addition, we have investigated a conduction mechanism resulting from the water protons, based on the frequency dependence of the BCN film impedance before and after water treatment.     

Atomic bonds in boron carbon nitride films synthesized by remote plasma-assisted chemical vapor deposition

Boron carbon nitride (BCN) films are synthesized by remote plasma-assisted chemical vapor deposition (RPCVD) method. The present experimental apparatus is featured by introducing BCl₃ gas near the substrate without mixing to plasma consisting of N₂ and CH₄ gases. Two sample groups of the BCN films are prepared. One is grown with various CH₄ flow rates, and another is grown with various BCl₃ flow rates. The composition ratio of the constituent atoms, atomic bonds and optical bandgap are investigated. C composition ratio of the BCN film increases with increasing CH₄ flow rate, leading to a reduction in the optical bandgap with increasing C composition ratio. On the other hand, it is found that no significant variation in the composition ratio occurs for the BCN films grown with various BCl₃ flow rates and that the optical bandgap decreases with increasing BCl₃ flow rate. This behavior of the optical bandgap is related to a change of the atomic bonds in the BCN film grown with various BCl₃ flow rates.     

Effects of annealing on low dielectric constant carbon doped silicon oxide films

Dielectric materials with lower permittivity (low k) are required for isolation to reduce the interconnect RC delay in deep submicron integrated circuit. In this work, carbon doped silicon oxide [SiO(C–H)] films are investigated as a potential low k material. The films were prepared by the radio frequency plasma enhanced chemical vapor deposition (PECVD) technique from trimethylsilane (C₃H₁₀Si or 3MS) in an oxygen (O₂) environment. SiO(C–H) films deposited with O₂ and 3MS flow rates of 100 sccm and 600 sccm, respectively have been previously found to produce dielectric constant as low as 2.9. This is attributed to the incorporation of carbon in the form of Si–CH₃ bond, which has lower polarizability compared to the Si–O bonds that were replaced. In this work, these low k films were annealed at 400, 500, 600 and 700 °C in a N₂ atmosphere for 30 min to determine the thermal stability of their properties. The films were characterized in terms of their thickness shrinkage, refractive indices, dielectric constants, infrared absorption, surface morphology and stress upon annealing. For annealing temperatures up to 500 °C, which is beyond the current highest processing temperature for back end of the line structure of around 450 °C, a slight decrease in the refractive indices and dielectric constants of the films are observed. The SiO(C–H) films also remain smooth and exhibit tensile stress with stress level that is within practical acceptable range. The results suggest that the SiO(C–H) films are thermally stable to be applied as low dielectric constant materials for deep submicron integrated circuit.     

Characterization of BCN film after wet process for interconnection integration

In this study, we investigate the influence of the wet chemical processes involved in the chemical treatment of boron carbon nitride (BCN) films deposited by plasma-assisted chemical vapor deposition (PACVD). BCN film is expected to be a low dielectric constant (low-K) material useful in fabricating future generation LSI devices. BCN film with less than 10% oxygen was hardly etched. The etching rate of the BCN film with an oxygen composition ratio more than 10% depends on the pH of the solution. The relationship between the film etching rate and the atomic bonds in BCN film is also investigated using XPS and FTIR. It was found that the BCN films without C–O and B–O bonds are not etched by acid and alkaline solutions. Therefore, suppression of oxygen concentration in the BCN film is important for LSI integration.     

Characterization of amorphous carbon films deposited by surface wave plasma CVD

Many dangling bonds in hydrogenated amorphous carbon (a-C:H) films are usually generated by bombardments of high-energy ion precursors in typical chemical vapor deposition (CVD). To generate low dangling bonds, a-C:H films should be deposited from low-energy radical species. Surface wave plasma (SWP) generates low-energy and high-density radicals. We prepare a-C:H films using SWP and investigate the relationship between the plasma characteristics and structures of a-C:H films. The microwave of the TM01 mode was introduced through the dielectric window and SWP generate under the dielectric window. An Ar and C₂H₂ plasma mixture mainly consists of neutral radical species, and the electron temperature is as low as 1 eV. Electron density significantly decreases with increasing distance from the dielectric window. The a-C:H films are prepared from these hydrocarbon and carbon low-energy radicals as main precursors. The sp² bonded network cluster size in a-C:H films increase with electron density in SWP. This structure change is the influence of the termination structure of clusters changing to CH from CH₃ and CH₂.     

Effects of acetylene addition on mechanical and dielectric properties of amorphous carbon films

The para-xylene added with acetylene from 15% to 50% was plasma polymerized at 50 to 150 W to deposit the a-C:H films. After the films were annealed from 200 to 400 °C, the network structure, hardness and dielectric constant of films were analyzed by FT-IR, Raman, nanoindentor and capacitance–voltage plot, respectively. Those measured results suggest that hydrocarbon bonds and oxygen related bonds of the a-C:H film effectively reduce and the number of ordered aromatic rings increases with decreasing the deposition power after annealing at 400 °C. In addition, both the dielectric constant and the hardness, respectively, increase up to 2.82 and 2.37 GPa, but the adhesion strength decreases with increasing the C₂H₂ concentration and deposition power. Therefore, the a-C:H films not only have a lower dielectric constant, but also have enough mechanical strength for the IC processing.     

What makes a dangling bond a binding site for thermal CH3 radicals? — A combined molecular dynamics and potential energy analysis study on amorphous hydrocarbon films

Identification of dangling bonds on amorphous films is not as straight forward as in the case of crystalline materials. The task is further complicated in the case of amorphous hydrocarbon (a-C:H) films by the existence of a wide variety of atomic arrangements. We present a technique based on potential energy analysis of a-C:H films to identify dangling bonds and physisorption sites. However, molecular dynamics simulations of the sticking of thermal CH₃ on a-C:H surfaces show that not all dangling bonds are binding sites for a CH₃ radical. Furthermore, the total sticking coefficient of the surface is not solely linked to the number of dangling bonds and can even decrease for the same number of dangling bonds because the carbon atoms that possess a binding site, active carbon atoms, show drastically different reactivity towards CH₃. The reactivity of active carbon atoms is decided by (a) their type, which is decided by the bonding partners, (b) their distance from the local surface and (c) the local environment. The reactivity of the active carbon atoms can be largely increased by energetic ion bombardment due to hydrogen depletion and local rearrangement.     

Dry etching properties of methyl-BCN film with C4F8 gas for Cu/low-k interconnection

Methyl-BCN is an attractive low-k material for the fabrication of next generation LSI device system. This paper describes dry etching of methyl-BCN film in order to develop interconnections for future devices. The methyl-BCN films were deposited by plasma-assisted chemical-vapor deposition (PACVD) using tris(dimethylamino)boron (TMAB) gas at 350 °C. We have investigated dry etching properties and mechanism of the methyl-BCN film using C₄F₈ gas with induced coupling plasma (ICP) etching equipment. In this study we used C₄F₈ gas whose atmospheric lifetime is less than one-sixteenth of the conventional CF₄ gas for suppression greenhouse gases. It was found that methyl bonds in the methyl-BCN film can be kept after dry etching, because the peak of C–H (2962 cm^?1) in Fourier transform infrared absorption (FTIR) spectra didn't significantly change after dry etching. X-ray photoelectron spectroscopy (XPS) analysis shows the presence of C–F₂ and C–F₃ bonds just on the methyl-BCN surface after dry etching and no traces of these bonds inside the film. It is observed that intensities of B–N and B–C bonds decrease after dry etching. This suggests that the etching of methyl-BCN films by C₄F₈ gas mainly involves boron desorption.     

Effect of ClH aromatic substitution on structural and dielectric properties of poly(p-xylylene)

A basic understanding of the structure–property relations and how they are influenced by the molecular architecture is imperative for the future development of polymer thin films in a large number of applications including those in the electronics industry. A new study has been illustrated in this work to demonstrate the effect of an aromatic Chlorine–Hydrogen substitution on the structural and dielectric properties of poly-para-xylylene (parylene N) ((–CH₂–C₆H₆–CH₂–)_n). X?Ray Diffraction (XRD) analysis reveals that the chlorination of the aromatic rings of poly-para-xylylene stabilize the crystalline structure of the materials (α–monoclinic), increases the d-spacing, decreases the crystallinity, and increases the value of the dielectric parameters. Furthermore, the permittivity is increased from 2.68 (PPX N) to 3.1 (PPX C) and the conductivity is increased by two order of magnitude at room temperature at frequency 1 KHz. Fourier Transformation Infrared Spectrometer (FTIR) and Energy Dispersion X-ray (EDX) analyses shows that the different as deposited parylene type are deprived of extrinsic polar bonds who can influenced on the dielectric properties. The increase of the dielectric properties and the changes of the morphologies structure are associated to the change in the intermolecular interaction due to the Cl_H aromatic substitution of poly-p-xylylene.     

Synthesis of methyl boron nitride film as low-k insulating film for LSI interconnection

Low dielectric constant (k) materials for the ULSI interconnect insulator are required to meet the fast development of high-speed devices. We have investigated low-k material of boron nitride containing methyl (methyl boron nitride) by using tris-di-methyl-amino-boron (TMAB) gas. The dielectric constant (k) of the film decreases with decreasing RF plasma power and the k value of the methyl BN film can be achieved as low as 1.8 at 10 W RF plasma power.Absorption band of the film was observed at 2960 cm^? 1 due to unsymmetrical stretching mode of C–H in CH₃. It is thought that increasing C–H bond with low polarizability and reducing CN bond with high polarizability can realize a lower k value. The film has also high resistivity of more than 1 × 10⁹ Ω cm and sufficient Young modulus of more than 26 GPa for the interlayer of LSI interconnection. There is a possibility that the dielectric constant can be decreased keeping the BN structure with high strength. The methyl BN film is an extremely attractive material as low-k material of next generation devices.     

Study on highly thermostable low-k polymer films based on fluorene-containing polyetherimides

Highly thermostable low-k polymer films with potential applications as dielectric materials in microelectronic industry were synthesized starting from 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride and various diamines. A polyetherimide/silica nanocomposite film was obtained using methyltriethoxysilane as precursor of inorganic phase. The chemical structure was confirmed by FTIR and ¹H NMR spectroscopy. Water vapor's sorption capacity, thermal stability, glass transition temperature, thermal diffusivity, specific heat, thermal conductivity, and dielectric characteristics of the films were determined. All the films exhibited excellent thermal stability, with an initial decomposition temperature in the range of 500–530°C. They showed low dielectric constant of 1.98–2.86 and low dielectric loss of 0.0037–0.011, at a frequency of 1 Hz and room temperature. The subglass γ- and β-relaxations, primary α-relaxation, and conductivity relaxation processes were discussed according to the chemical structure of the samples. Quantitative structure–property relationship (QSPR) study was conducted, and linear regression models were formulated to describe the causal relationships between different parameters and polyetherimide properties.     

Surface modification of nanocrystalline diamond/amorphous carbon composite films

The surfaces of nanocrystalline diamond/amorphous carbon (NCD/a-C) nanocomposite films deposited from a 17% CH₄/N₂ mixture have been subjected to a variety of plasma and chemical treatments, namely H₂ and O₂ microwave plasmas, a CHF₃ 13.56 MHz plasma, and a chemical treatment with aqua regia (HCl:HNO₃ 3:1). The resulting surfaces have been studied with respect to their chemical nature by X-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (TOF-SIMS), concerning their morphology with atomic force microscopy, and by contact angle measurements to study their hydrophobicity and their stability. As-grown surfaces are hydrogen terminated, but the number of C–H bonds can slightly be increased by a H₂ microwave plasma, while treatment with aqua regia considerably lowers the number of C–H bonds at the surface. O₂ and CHF₃ plasmas, on the other hand, lead to a replacement of the terminating C–H bonds by C–O or C–OH and C–F_x groups, respectively. Finally, by contact angle measurements over a period of 150 days it could be shown that the H-terminated surface is very stable whereas the contact angle of the O-treated surface changed considerably with time, probably due to the adsorption of contaminants.     

Influence of oxygen plasma treatment on properties of Methyl-BCN film

Methyl-BCN film as a low dielectric material has been investigated by our group for Cu/low-k interconnection. We studied the ashing characteristics of Methyl-BCN films using oxygen plasma. As a contrast, porous-SiOCH films were also treated by oxygen plasma with the same conditions. The change of composition ratio of Methyl-BCN film is less than that of porous-SiOCH film after oxygen plasma treatment. There is no evident change in each bond of Methyl-BCN film after treatment, either. FT-IR analysis was carried out to investigate the chemical bonds of Methyl-BCN films and porous-SiOCH films with and without oxygen plasma treatment. The methyl groups of Methyl-BCN film were more stable than that of porous-SiOCH film.     

Microstructure and tribological properties of ternary BCN thin films with different carbon contents

Boron carbon nitrogen (BCN) thin films with different carbon contents are deposited on high-speed steel substrates by reactive magnetron sputtering (RMS) and their microstructure and tribological properties are studied. The BCN films with carbon contents from 26.9 wt.% to 61.3 wt.% have an amorphous structure with variable amounts of carbon bonds (sp²C–C, sp²C–N and sp³C–N bonds). A higher carbon content enhances the film hardness but reduces the friction coefficient against GCr15 steel balls in air. BCN films with higher hardness, lower friction coefficient, and better wear resistance can be obtained by increasing the carbon content.     

Influence of K2CrO4 Doping on the Structural,Optical and Dielectric Properties of Polyvinyl Alcohol/K2CrO4 Composite Films

Polyvinyl alcohol/potassium chromate (K₂CrO₄) composite films were prepared by solution casting technique using distilled water as a solvent, and were further investigated using Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, X-ray diffraction, thermogravimetric analysis, optical microscopy, scanning electron microscopy, and dielectric measurements. Microscopic studies reveal that K₂CrO₄ was homogenously mixed with polyvinyl alcohol matrix due to interfacial interaction between polyvinyl alcohol and K₂CrO₄. The composite films showed very high dielectric constant and relatively low dielectric loss. Hence, such composite materials with improved dielectric properties could be useful for fabrication of electrical charge storage device.     

Micromechanical properties of BN and B–C–N coatings obtained by r.f. plasma-assisted CVD

We have obtained highly transparent and hard BN films in a capacitively coupled r.f. plasma-assisted CVD reactor from three different gas mixtures: B₂H₆–H₂–NH₃, B₂H₆–N₂ and B₂H₆–N₂–Ar. It was found that the films were smooth, dense, and had a textured hexagonal structure with the basal planes perpendicular to the film surface. The microhardness, friction coefficient and adhesion of these coatings were measured by nanoindentation and microscratching. BC_xN_y films were also prepared in the same plasma-assisted CVD reactor from B₂H₆–N₂–CH₄ gas mixtures. The carbon content in the films was varied by using different CH₄ flow rates. These films had a less ordered structure. The mechanical properties of these films had been compared to those of hexagonal BN films. Microhardness measurements showed that there is a correlation between film composition and hardness of the BCN films.     

Aqueous Solution–Gel Preparation and Dielectric Properties of Ba(Mg1/3Nb2/3)O3 Thin Films with Long‐Range Order

In the present research, the Ba(Mg_1/3Nb_2/3)O₃ (BMN) thin films with high 1:2 long‐range order (LRO) were prepared by an entire aqueous solution–gel route and a heat treatment at low temperature. The BMN precursor solutions used for spin‐coating consist of tri‐metal ions citrate complexes, which are formed through the combination of three single citrate complexes with NH₄⁺ acting as crosslinks. The metal‐coordinated bonds of the citrate complexes can be easily broken by heat treatment, which can result in the crystallization of BMN films at low annealing temperature. The crystalline structure and LRO degree of BMN films were also investigated. It is shown that the LRO degrees increase with the increase in annealing temperature. The dielectric constant increases and the dielectric loss decreases with the annealing temperature up to 750°C due to the improvement of the film densification and the LRO degree. The further increase in annealing temperature slightly decreases the dielectric constant and increases the dielectric loss due to the appearance of large aggregates. It is shown that the charge carriers mainly contribute to the dielectric response below 100 KHz, while the dipolar response starts to take effect for the frequency higher than 100 KHz.     

A new method for the synthesis of disilylalkanes by Kolbe anodic oxidation of α-silylcarboxylic acids

A new method has been developed for the synthesis of disilylalkanes by Kolbe anodic oxidation of α-silylcarboxylic acids. Preparative electrolysis was carried out by constant current technique. The effect of various parameters (electricity consumption, current density, temperature, solvent, base and concentration of substrate) on the outcome of electrolytic process has been studied and evaluated. On the basis of optimal conditions found, the synthesis of three dimeric products Ph₂(Me)SiCH₂CH₂Si(Me)Ph₂, Ph(Me)₂SiCH₂CH₂Si(Me)₂Ph and Me₃SiCH₂CH₂SiMe₃ was achieved in good yields by anodic decarboxylation of the corresponding acids Ph₂(Me)SiCH₂CO₂H, Ph(Me)₂SiCH₂CO₂H and Me₃SiCH₂CO₂H.     

Influence of the substrate on the phase composition and electrical properties of 0.65PMN–0.35PT thick films

Thick films with the nominal composition 0.65Pb(Mg_1/3Nb_2/3)O₃–0.35PbTiO₃ (0.65PMN–0.35PT) were produced by screen-printing and firing paste prepared from an organic vehicle and pre-reacted powder. The films were fired for 2 h at 950 °C on alumina (Al₂O₃), platinum (Pt), aluminium nitride (AlN) and 0.65PMN–0.35PT substrates. The films were then characterized using scanning electron microscopy, X-ray diffraction and dielectric constant measurements. The X-ray analysis did not detect the presence of any undesirable pyrochlore phase, and the differences in the phase compositions were determined with a Rietveld refinement. The variations of the cell parameters vs. the temperature for the monoclinic and tetragonal phases were calculated. It was demonstrated that under similar processing conditions the microstructures, phase compositions and dielectric properties strongly depended on the stress in the thick films due to the different temperature expansion coefficients of the thick films and the substrates. The 0.65PMN–0.35PT thick films under compressive stresses (for the case of the Al₂O₃ and Pt substrates) exhibited a tetragonal phase in addition to the monoclinic one. The films were sintered to a high density and with a coarse microstructure. These microstructures favour a high dielectric constant. In contrast, for the films under a tensile stress, like the films on AlN substrates, the films were sintered to a lower density and the microstructure consisted of smaller grains. The X-ray analysis showed mainly a monoclinic phase, while the tetragonal phase was not detected. These results indicate the importance of the stresses in 0.65PMN–0.35PT thick films and their influence on the structural and electrical characteristics of the films.     

A novel proton transfer supramolecular compound induced by N–H⋯O hydrogen bond through 18-crown-6: Syntheses,structures, and dielectric properties

A novel organic–inorganic hybrid supramolecular compound, [(4-Nitroanilinium)(18-crown-6)][BF₄](CH₃CN), was prepared via H-bond dipole interactions between 4-nitroanilinium, 18-crown-6, and BF₄⁻, in acetonitrile solution. N–H…O hydrogen bonds between neighboring 4-nitroanilinium cations and 18-crown-6 were observed. However, the formation of one-dimensional supramolecular chain structure via N–H…O that contacts through the cavity of 18-crown-6 was worth noting. A strong dielectric response was observed above 300 K at a low frequency of 500 Hz, thereby suggesting the proton transfer in the N–H…O bonds.