Silica thin films have been processed via a colloidal sol‐gel method which involves the hydrolyzing of potassium silicate and colloidal silica sol using formamide[l]. The resulting films are highly porous. The processing leaves residual potassium and sodium in the films which can then be removed through leaching in water. The dielectric properties of films which have been leached for twenty minutes are nearly insensitive to humidity. However, partially leached films, or films which have been doped with LiCl, KC1, or NaCl, are highly sensitive to humidity changes. The range of humidities over which these films have high sensitivity can be modified by changing the dopant type or varying the doping level. Films can be made to sense humidities ranging from 20% to 80% reproducibly. These films are ideal for microelectronic applications because they can be processed via dipping as well as spin coating and can also be easily etched.

SiO2 insulator was fabricated by using Xe2* excimer lamp at room temperature. In this method, a mixrine of NF3 and O2 gases was employed as a reaction gas. When the NF3 and O2 gases were exposed to the Xe2* excimer lamp light NF3 and O2 gases inside the chamber where Si substrate was placed, SiFn and NO2 were produced by photo‐chemical reaction. The SiFn accumulates on the Si substrate, and SiO2 is formed by oxidation reaction between SiFn and NO2. Subsequently SiFn adheres onto the formed SiO2 and again oxidizes by NO2. These processes occur spontaneously, and on SiO2 film is grown. Experimental conditions were NF3:O2 = 10:1, the total gas pressure 330 torr, photo‐chemical reaction time 5 minutes, and chain reaction time 5 minutes. The results of the film characterization were a SiO2 film thickness of about 1500Å, a refractive index of 1.38, specific resistance of 1.67*1010 Ω cm and relative dielectric constant of 6.96.

A thermodynamic simulation is presented of the low pressure chemical vapor deposition (LPCVD) of silicon oxide thin films starting from TEOS and N2O mixtures within the temperature range 700 – 1300K, by minimizing the total Gibbs energy of the C‐H‐N‐O‐Si chemical system. It was found that at temperatures up to 1173K and N2O/TEOS molar ratios up to approximately 7, SiO2 films contain carbon impurities, while above this ratio deposits are carbon free. A corresponding experimental investigation is also presented where the obtained submicronic films are slightly substoichiometric in oxygen. They contain small carbon impurities the concentration of which decreases with the N2O/TEOS molar ratio.

Tantalum pentoxide (Ta2O5) films were deposited from the reaction of tantalum pentaethoxide (Ta(OC2H5)5) and oxygen (O2) using the Lam Research Corporation DSM™9800 advanced LPCVD reactor. Typical films were deposited at a rate of 0.9 – 1.1 nm/min at 400°C. The films were stoichiometric with an O/Ta ratio of 2.57/1.00 and excellent compositional uniformity. Conformity was >95% indicating that the process is surface reaction rate limited. Films with non‐uniformities <2.2% were deposited on 300 mm wafers. The deposited non‐uniformity on 150mm and 200mm wafers was <2.0% ‐1σ within a wafer, wafer to wafer within a batch, and batch to batch. The dielectric constant for as‐deposited films was 22–24, and as high as 34 for films which were heat treated. Various post deposition heat treatments were performed to improve the capacitor's electrical properties. Superior results were obtained from rapid thermal annealing (RTA) in N2O compared with RTA in O2 and two‐step UV‐O3 followed by high temperature annealing in dry O2. Values for the leakage current of <10-8 A/cm2 at 1.2 volts negative bias (worst case) and breakdown >5 MV/cm at 1.6μΑ with tegox<2.5 nm have been obtained. These values meet the requirements for 256 Mbit DRAM memory devices Bottom and top electrode formation and integration issues are also addressed.

An all‐alkoxide route to SrBi2Ta2O9 (SBT) thin films and powders was developed. While stoichiometric gels transformed to single‐phase SBT, excess bismuth was required to obtain single‐phase SBT films on Pt substrates. An annealing temperature of 800 °C in O2 for 2 minutes was required to crystallize the films. Electrical measurements of SBT films produced under these conditions showed that films less than 2000 Å in thickness were shorted, while films of 3000 to 5000 Λ had a dielectric constant of~ 300. RBS measurements of a bismuth titanate film on Pt indicated that Pt diffuses into the dielectric layer when annealed at 700 °C in O2 for 1 minute, suggesting that interfacial reaction of these layered bismuth materials may be significant.

Nanoscale oxide thin films such as Ba1‐xSrxTiO3 (BST), SrBi2Ta2O9 (SBT), and PbZr1‐xTixO3 (PZT) that have a high dielectric constant and excellent ferroelectric properties have been receiving greatly increased attention, especially for high density memories in next generation integrated circuits. However, with increasing deposition temperature the surface roughness of the films increases, which results in high leakage current, and when the thickness of oxide films is decreased, the apparent bulk‐like properties of thin films tend to worsen due to the increased influence of the interface. To solve these problems, novel MOCVD techniques, plasma enhanced deposition, and a two step process, were developed for high quality oxide thin films.

Metal ß‐diketonate complexes are common precursors for chemical vapor deposition (CVD) of a wide variety of thin‐film materials. Liquid delivery CVD has been used to deposit high dielectric constant materials, such as BaxSr1‐xTiO3.[1] This method relies upon volumetric metering of organic soluble precursors, “flash” vaporization to transport the reactants into the gas‐phase and subsequent thermal decomposition onto the heated substrate. This approach enables the precise control of deposited film stoichiometry. In this study, simultaneous thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to examine the transport and thermal decomposition properties of M(thd)2 (M = Sr, Ba) and Ti(O‐i‐Pr)2(thd)2. In an argon atmosphere, vaporization and transport are observed below 400 °C. In oxidizing atmospheres, such as nitrous oxide and oxygen, decomposition leads to metal carbonate formation as evidenced by both the mass balance and x‐ray diffraction patterns of the residual solids. In the presence of an equimolar amount of the Ti precursor, the formation of carbonates is not observed and oxides are produced at greatly reduced temperatures. Based upon this data, a cooperative oxidation mechanism is proposed which results in “clean” precursor decomposition and BST oxide formation at temperatures near 500 °C.

High-purity alkaline earth ß-diketonate compounds such as [M(thd)2]x (M = Mg, Ca, Sr, Ba) have been utilized for liquid delivery MOCVD.[1] The “parent” compounds are oligomeric species with bridging ß-diketonate ligands and display both limited volatility and thermal instability. To enhance the precursor transport and film growth rates, Lewis base ligands are used to produce mononuclear precursors.[2] Lewis base coordinated metal (ß-diketonates) also exhibit increased solubilities in organic solvents. In this study, two classes of Group II ß-diketonates were compared; thermal stability and transport were evaluated by simultaneous thermal analyses, using both thermogravimetric (TGA) and differential scanning calorimetry (DSC). Liquid delivery and vaporization were evaluated in an “experimental” liquid delivery system and preliminary film growth, including electrical film properties were measured. The identity of the Lewis base and Group II precursor molecular structure as relates to liquid delivery vaporization and CVD film growth of BaxSr1–xTiO3 are described.

Insulating thin films of Bi2Ti2O7 with (111) orientation have been prepared on silicon (100)–substrates at a temperature range of 480–550 °C by a MOCVD technique. The dielectric and C‐V properties were studied. The dielectric constant (ɛ) and loss tangent (tanδ) were found to be 180 and 0.01, respectively. The temperature and frequency dependence of dielectric constant were also measured. The Bi2Ti2O7 films are suitable to be used as a novel buffer layer and new insulating gate material in FET devices.

A new sol‐gel route to obtain PLZT thin film was developed by combining the advantage of 2‐methoxyethanol as a solvent and acetylacetone as a chelating agent. The sol maintained the same stable state as that of fresh synthesized sol even after 60 days of aging. The PLZT films spin coated onto a Pt/Ti/SiO2 substrate with 15% Pb excess and 7.5% La added sol showed well developed rosette microstructure of uniform grain sizes(0.3 ‐ 0.5 μm) and gave well behaved ferroelectric properties with the values of Ps, Pr, and Ec of 40 μC/cm2, 15 μ C/cm2, and 20 kV/cm respectively at 5V after 650 °C and above annealing. The degradation in polarization of 2.5% La doped PLZT thin film was found to be less than 20% up to 1012 cycles

BaTiO3 films prepared by RF sputtering was studied for capacitor applications. Some films produced have a capacitance storage of 0.85 μF/cm2, a high resistivity of 1014 ω‐cm, and a low dissipation factor of 0.005. The dielectric constant of these BaTi03 films were approximately 10 to 30, which is superior to that of the typical polymer film capacitor and had little dependence on frequency. However the breakdown strength of BaTi03 was approximately 5MV/meter. The theoretical breakdown strength of BaTi03 is reported to be as high as 200MV/m. The processing parameters of BaTi03 films must be optimized to obtain the potential benefit of the BaTi03.

BaTiO3 epitaxial films have been prepared on (001) MgO substrates by metalorganic chemical vapor deposition. The as‐deposited 0.2 μm thick films had a surface roughness of 12 nm. Channel waveguides were fabricated from the films and the optical throughput measured. To differentiate the surface scattering loss from the internal scattering loss, waveguides were also prepared with a surface planarization step to reduce the surface roughness to 2.5 nm. The waveguide loss was greatly reduced for the planarized waveguides. The results indicate that surface and side wall roughness accounted for the majority of the waveguide loss. Grain boundary grooving lead to surface roughness and routes to overcome this problem are discussed.

BaTiO3 (BT) thin films were prepared by flash evaporation onto p‐Si and SiO2/p‐Si. The films are amorphous and remain so after a thickness reduction by 20% by annealing at 500 °C for 3 min. in O2 atmosphere. The electrical characteristics were measured at room temperature.

Electron injection at the Al to BT interface of Al/BT/Si capacitors is enhanced by the Schottky effect, yielding a value of 11.2 for the dielectric constant of BT. Modeling current‐time measurements yields a trap density of 1024 m3, 0.82 eV below the conduction band. Capacitance‐voltage curve shifts due to bias stress on AI/BT/SiO2/Si capacitors are interpreted as caused by electron injection and trapping in the BT films. Starting deposition at 170 °C or post‐deposition annealing reduces the trap density and increases the C‐V curve shifts by bias stress, from 0.3 to over 14 V at bias stress of‐10 V.

Ferroelectric lead zirconate titanate (PZT) thin films have been successfully prepared on a RuOx/Pt multilayered electrode by Metal Organic Chemical Vapor Deposition (MOCVD). The multilayered electrode was introduced to enhance device reliability for FRAM and DRAM applications. The variations in the microstructure and ferroelectric properties of the PZT thin films were investigated as a function of substrate thickness. The microstructure of the PZT thin films was found to have a strong dependence on the surface morphology of the substrate. The control of microstructure resulted in improved ferroelectric properties. The endurance of the Pt/RuOx/PZT/RuOx/Pt capacitor was also maintained up to 1010 cycles without any serious degradation. The ferroelectric capacitors on 4” wafer were integrated by using Inductively Coupled Plasma Reactive Ion Etching (ICP RIE) system and the fully processed MOCVD PZT capacitors showed good ferroelectric properties (Vc=0.57V, ργ=22μC/cm2 respectively).

Spectroscopic Ellipsometry (SE) and Grazing X‐ray Reflectance (GXR) techniques are applied for different insulating films to determine precisely the thickness and optical indices of the layers. Antireflective coatings for microlithography in the DUV range are first analyzed. In the infrared range the layers are transparent and one can take into account the optical index of the layers by a simple dispersion law. Thicknesses obtained by this method are checked by the GXR technique. Extraction of the optical indices from UV to IR is made very accurately taking into account different SE measurements at various incident angles simultaneously. Amorphous carbon thin films are also analyzed in the same way. The main difference is that the layer is absorbant in the entire wavelength range. In this case, a first characterization by the GXR technique is essential to extract the thickness of the layer. Then the optical indices of the layer can be extracted very accurately by SE.

Several layered inorganic materials (e.g. KCa2Nb3O10, KTiNbO5, and CsPb2Nb3O10) were prepared and their alkali cations exchanged by in aqueous acid. A fraction of the interlayer protons of HCa2Nb3O10 and HTiNbO5 can be replaced by tetra-n-butylammonium (TBA+), by reaction with TBA+OH. Intercalation of a sufficient amount of TBA+ causes complete exfoliation, and single, nanometer-thick sheets of these materials are thus obtained. By sequential adsorption of these two-dimensional colloidal polyanions and polymeric cations, monolayer sheets of layered perovskites can be stacked on silicon surfaces to give thin films of any desired thickness. The layered materials, the exfoliated colloids, and the thin film multilayers on silicon were studied by X-ray diffraction, transmission electronic microscopy (TEM), ellipsometry, and atomic force microscopy (AFM). The dielectric properties of the related bulk materials were measured, and are also discussed.

Films of amorphous aluminum oxide were deposited from vaporized alkylaluminum alkoxide compounds and oxygen. For example, a gaseous mixture of triethyldialuminum tri-sec-butoxide vapor and dry air deposits amorphous aluminum oxide films on substrates heated to temperatures around 400 °C. Transparent, smooth, adherent films of aluminum oxide were formed on silicon, glass and metal substrates. The new precursors display a number of advantages over previously used sources for aluminum oxide. They are non-pyrophoric, low-viscosity, low-cost liquids. High deposition rates, over 0.2 μm/min, were observed. The coatings have high purity, high electrical resistivity and high transparency to light. They are excellent barriers to diffusion of water and of ions, such as sodium. These films are useful in optical coatings, as wear-resistant hard coatings, and as diffusion barriers that protect flat panel displays, computer microcircuits, solar cells and metals from corrosion and degradation by impurities.

A novel single-source MOCVD technique was used to deposit Ce:YIG ((Ce,Y)3Fe5O12) films which were investigated for integrated magneto-optical applications, such as waveguide isolators. These films were grown on gadolinium gallium garnet substrates in order to optimize the growth conditions before growth on semiconductor substrates was attempted. We were able to achieve very high ratios of Ce:Y (= 0.4) due to the nonequilibrium nature of MOCVD. Ce:YIG films on GGG substrates were epitaxial with excellent optical and magnetic properties, along with high Faraday rotations that were comparable to commercial Bi:YIG. Planar waveguiding was observed in Ce:YIG films on both GGG and MgO substrates. MgO also proved to be a successful buffer layer for protecting the semiconductor substrates during YIG deposition. The Ce:YIG films on MgO-buffered GaAs had very promising magnetic properties, but the MgO deposition on InP must be optimized before successful Ce:YIG films on InP can be achieved.

A thermodynamic model previously outlined for the prediction of the bonding in amorphous hydrogenated carbon-nitrogen alloy films (a-CxNyHz), is extended here to include the effects of enthalpy and entropy. Predictions are presented for the bonding of tetrahedral C(sp3), trigonal C(sp2), pyramidal N(sp3), and trigonal N(sp2) atoms in the alloy as well as the bonding of H to these atoms. When bond energies alone are considered, it is predicted that typical a-CxNyHz films will undergo a phase separation into graphitic regions containing C(sp2) atoms, and C(sp2)-N(sp3)-H groups, and diamond-like or polymeric regions containing only C(sp3) and H atoms. When the effects of entropy are also included, phase separation is eliminated and C(sp3)-C(sp2), C(sp2)=N(sp2), and C(sp2)-N(sp2), bonds are also predicted to be present. The model predictions are compared with experimental results for typical amorphous a-CxNyHz alloys that have been prepared via plasma-enhanced chemical vapor deposition from mixtures of nitrogen and acetylene. In a film with y=0.07 the carbon atoms sp3/sp2 ratio is predicted to be 0.7, while 80% of N atoms are predicted to be trigonal N(sp2) atoms.

We have investigated the changes in the temperature dependence of the dc conductivity and the optical gap with nitrogen content in amorphous carbon nitride (a-C:N) films, in order to find the effect of nitrogen doping on the electrical and optical properties of amorphous carbon films. Specimens were deposited onto borosilicate glass substrates by the rf magnetron sputtering method using Ar and N2 as a sputtering gas and a reactive one, respectively. The values of the activation energy of the dc conductivity, Ea, of these films are 0.3∼0.8 eV and those of the optical gap, Eg, are 0.8∼ 1.4 eV. Both values decrease with increasing nitrogen content, which is due to the increase of the concentration or average size of sp islands segregated into the sp matrix by nitrogen doping. From the investigation of the behavior of both Ea and Eg in accordance with the nitrogen content, we discuss the three subsequent shifts of band edge and Fermi level, accompanied with the subsequent changes of microstructure in a-CN films by nitrogen doping.