T.K.S. Wong

Atomic structure and defect densities in low dielectric constant carbon doped hydrogenated silicon oxide films, deposited by plasma-enhanced chemical vapor deposition

Results of structural characterization by Fourier transform infrared spectroscopy, x-ray diffraction, and specular x-ray reflectivity measurements are employed for the interpretation of electrical measurement data and the deconvoluted distribution of electron states, N(E) of carbon doped hydrogenated silicon oxide (SiOCH) low-k dielectric films. Atomic structure of the films is identified as a mixture of a dominant and totally amorphous SiO2-like phase with a partially polycrystalline SiC phase. The n-type dc conductivity that dominates in this material points to the principal role of the SiC-like phase in the dc transport of the SiOCH material. The deep level transient spectroscopy technique is applied for the N(E) shape studies in the energy range up to 0.7 eV below the conduction band bottom. Typical N(E) values lie in the 1010–1014 eV−1 cm−3 range for films deposited at different ratios of tri-methyl-silane to oxygen flow rate. No correlation between the N(E) shape and the film deposition conditions h...

Surface modified silica mesoporous films as a low dielectric constant intermetal dielectric

Silica mesoporous films with low dielectric constant were successfully fabricated by a multiple-step sol–gel process. Various surface modifications were conducted to make the surface of the films hydrophobicity, which was proved very effective to maintain the low dielectric properties of the films. The basic properties of the silica films were evaluated by atomic force microscopy, specular x-ray reflectivity, Fourier transform infrared, and thermal gravimetric and differential thermal analysis. An inherent low dielectric constant of around 2.0 was realized for about 56% porosity of the silica film with pore size less than 40 nm and the leakage current was at a level of 10−6 A/cm2 after two months of fabrication. Preliminary results of the silica films prepared here present a very positive prospective to intermetal dielectric applications.

The effect of TEOS/MTES ratio on the structural and dielectric properties of porous silica films

This paper presents the results of the characterization of porous silica films used as intermetal dielectrics. The films were fabricated via sol-gel process using tetraethyl orthosilicate (TEOS) and methyltriethoxysilane (MTES) as precursors with acid and base as catalysts. Several advanced techniques such as transmission electron microscopy, specular X-ray reflectivity, Fourier transform infrared spectroscopy, nitrogen adsorption, thermal gravimetric, and differential thermal analysis have been employed to obtain information on the structural properties of the films and reaction mechanisms involved in the sol-gel process of such dielectrics. The characterization results show the effects of the TEOS/MTES ratio on the development of the porosity, pore size, and pore interconnectivity of the films, which reflects the influence of different mechanisms of hydrolysis and condensation of silica precursors in different pH conditions and the existence of covalently bonded organic ligands on the pore structure. An inherently low dielectric constant of around 2.0 was realized for about 60% porosity in the silica films. The pore sizes were less than 10 nm with majority of pores being closed-cells.

Synthesis of organically modified mesoporous silica as a low dielectric constant intermetal dielectric

Silica mesoporous films with low dielectric constant were successfully fabricated by a multiple step sol-gel process. The employment of inorganic/organic precursors proved very useful in preventing the film from cracking. The acid/base two-step catalysis could adjust the refractive index or porosity of the silica films effectively and easily. The basic properties of the silica films were evaluated by transmission electron microscopy, specular x-ray reflectivity, Fourier transform infrared spectroscopy, and thermal gravimetric and differential thermal analysis. An inherently low dielectric constant of around 2.0 was realized for about 57% porosity in the silica film with a pore size less than 10 nm. The leakage current was at a level of 10−6 A/cm2 one month after fabrication. The dependencies of the dielectric properties of the films on the relative amount of the components in the starting solution and on the processing temperature were investigated in detail. Preliminary results of the silica films prepar...

Effect of aqueous and organic solvent ratio on the electropolymerization of bithiophene in the mixed solutions

Abstract The use of suitable ratio of water to acetonitrile could lower the onset oxidation potential of bithiophene to about 0.6 V vs. Ag/AgCl in the aqueous/organic mixed solution. This means that bithiophene can be electropolymerised at very low potential in such solutions, which is usually unachievable in pure organic media. When the current density for electropolymerisation was kept constant as 1.0 mA/cm 2 , the electropolymerization potentials for bithiophene could be tuned to stable values of 0.8, 0.9, and 0.94 V by keeping the volume ratio of water to acetonitrile as 2:1, 1:1, and 1:4, respectively in the mixed solution. Evidence shows that the chemical structure of polybithiophene synthesised by this technique is very similar to that of the polymer formed in organic media. The volume ratio of water to acetonitrile has a significant effect on electropolymerization of bithiophene as well as on the electrochemical properties and morphology of the polybithiophene films.

Synthesis and Characterization of Templating Low Dielectric Constant Organosilicate Films

The porous hydrogen methyl silsesquioxane films have been successfully synthesized by the incorporation of poly(amidoamine) (PAMAM) which is thermally decomposed to form nanometer-scale voids within the films. A coupling agent was used to prevent the phase separation of the sacrificial material and the matrix by chemically bonding them together. The decomposition behavior of PAMAM was studied in different atmospheres, and it was found that PAMAM degraded more effectively in air than in nitrogen. Atomic force microscopy and transmission electron microscopy micrographs provided information about the structure of the hybrid films, and specular X-ray reflectivity was used to evaluate the density and porosity of the films. A dielectric constant as low as 2.2 was achieved for closed-cell mesoporous film with PAMAM loading of 15 wt %.

Low Dielectric Constant Organosilicate Films Prepared by Sol-Gel and Templating Methods

Low dielectric constant organosilicate films with controllable microstructure have been successfully synthesized by multiple-step sol-gel process and templating method, which are the two basic methods to establish porous network in the films. Ultra-low dielectric constant (k) of around 2.0 can be achieved for both films. The microstructure such as porosity, pore interconnection and pore size of the two types of the films have been studied and compared. It has been found that the sol-gel films have a higher level of porosity comparing to the templating films to obtain the same k value. The sol-gel film has a majority of closed pores with pore size around 5 nm. The templating film has a closed pore structure with pore size around 10 nm. Preliminary results present a very positive prospective for intermetal dielectric applications.

Influence of surface roughness and internal strain on defect spectrum and intensity of low-temperature photoluminescence of thin Si1−xGex layers

Microstructure, surface roughness, morphology, defect spectrum, and low-temperature photoluminescence of thin (10–125 nm) strained Si1−xGex layers (0.1⩽x⩽0.3), deposited by chemical vapor deposition (CVD) at 650 °C on silicon wafers have been studied. Nominally undoped layers with crystalline orientations of 〈100〉 and 〈111〉 have been investigated. Local strain within the layers was estimated from x-ray diffraction data. It decreases with the layer thickness in the 〈100〉-oriented samples, but rises in the 〈111〉-oriented ones. Nanoscale (∼10–30 nm) and microscale (∼0.2–1 μm) morphologies have been found on the surface of the Si1−xGex layers by atomic-force microscopy. The lateral sizes of the morphologies and surface roughness depend on the thickness, germanium concentration x, and crystalline orientation of the layers. The spectrum of defect states N(E) in the band gap of these samples has been experimentally studied by the deep-level-transient-spectroscopy (DLTS) technique. The standard D1(P1), D2, P3, an...

Effects of Plasma Treatments on Ultralow-k Dielectric Film and Ta Barrier Properties in Cu Damascene Processing

This work investigates the modification in structure, composition, and electrical properties of a porous methyl-silsesquioxane (P-MSQ) ultralow-k dielectric film when exposed to different gas plasmas that are typically used in a copper dual damascene process. Wafers with spin-coated P-MSQ films with dielectric constant (k ≈ 2.2) were treated with different plasma chemistries: O 2 , H 2 /N 2 , C 4 F 8 , and H 2 /He. The changes in film properties such as surface roughness, hydrophobicity, dielectric constant, chemical bonding, and elemental composition after the plasma treatments were evaluated. It was found that both leakage current density and breakdown voltages deteriorated after the plasma treatment. The worst case was that of a combination of fluorocarbon etching and H 2 /He stripping plasmas wherein the leakage current density increased by five orders of magnitude and the breakdown field decreased by about 20%. The leakage current was partially reduced by adding an ultrathin dielectric capping layer to the plasma-treated film. The Ta barrier film microstructure deposited on the plasma-treated P-MSQ correlated with the surface roughness of the film. The Ta films deposited on fluorocarbon plasma-treated samples had the largest surface roughness and relatively less crystalline microstructure compared to Ta film deposited on nonfluorocarbon-based, plasma-treated samples.

Deep-ultraviolet resist contamination for copper/low-k dual-damascene patterning

Deep-ultraviolet (DUV) lithography is the preferred technique for high-resolution patterning at sub-180 nm technology nodes. The via first (VF) dual-damascene (DD) process is the most commonly used integration scheme for realizing the copper interconnects. A major problem encountered with the use of the DUV photoresist in the VFDD process is the presence of resist residues, also known as resist contamination or resist poisoning, which are difficult to remove after trench lithography. In this study, the causes of the DUV-resist contamination for a low-k organosilicate SiOC:H dielectric have been investigated. The effects of different types of underlying substrates and processes used for forming the DD structures on the resist contamination are studied and the physical mechanisms responsible for formation of resist residues are identified. The post via-etching solvent cleaning process is identified as a major contributor to resist contamination and solutions are proposed to minimize DD-process-induced DUV-resist contamination.Deep-ultraviolet (DUV) lithography is the preferred technique for high-resolution patterning at sub-180 nm technology nodes. The via first (VF) dual-damascene (DD) process is the most commonly used integration scheme for realizing the copper interconnects. A major problem encountered with the use of the DUV photoresist in the VFDD process is the presence of resist residues, also known as resist contamination or resist poisoning, which are difficult to remove after trench lithography. In this study, the causes of the DUV-resist contamination for a low-k organosilicate SiOC:H dielectric have been investigated. The effects of different types of underlying substrates and processes used for forming the DD structures on the resist contamination are studied and the physical mechanisms responsible for formation of resist residues are identified. The post via-etching solvent cleaning process is identified as a major contributor to resist contamination and solutions are proposed to minimize DD-process-induced DUV-r...