Chemically vapor deposited borophosphosilicate glass (BPSG) has been widely used in microelectronic device fabrication as interlayer dielectric film due to its excellent planarization, gettering and flow properties. With device geometry reducing to sub micron levels, there is an increasingly greater emphasis on detection and elimination of sub micron defects particularly on deposited film. In this paper, we report on the evaluation and characterization of the surface roughness of BPSG films of various thicknesses and film compositions deposited on Si substrates using the Atomic Force Microscopy (AFM). The effects of high temperature densification process on the surface roughness are presented. The defect detection capabilities of conventional laser-based particle counters with respect to the surface roughness of BPSG films are investigated.

Atomic Force Microscopy has been used to observe the details of surface morphology on CdxHg1-xTe epitaxial films. On films grown by liquid phase epitaxy (LPE), tiered pyramidal features were observed and these are consistent with enhanced nucleation and growth at emergent edge dislocations which thread through from subgrain boundaries in the substrate. On films grown by metal-organic vapour phase epitaxy (MOVPE) using the interdiffused multilayer process (IMP), terraces and steps are observed as expected but the step edges are decorated. It is suggested that this corresponds to the deposition of one binary layer in Volmer-Weber mode.

Preliminary results from a study of the morphology of the MgO (100) surface after chemical etching followed by heat-treatment in air are presented. Contrast arising from the surface-steps so formed is found to be strongly dependent on the deviation parameter, suggesting that many of the step-faces are not perpendicular to the (100) foil plane but are, instead, often rather shallowly inclined.

X-ray specular and non-specular scattering, and high-resolution transmission electron microscopy (HRTEM) were performed to study the evolution of the microstructures and interfacial roughness in Ru/C and RU/B4C multilayers upon annealing. The microstructure of the approximately 1.4 nm thick Ru layers in the as-prepared 3.5 nm period multilayers is predominantly amorphous. The Ru layers in the Ru/B4C multilayer show RuB2 nano-crystallites after annealing at 600°C for one hour, while those in the Ru/C multilayer crystallize to form hexagonal Ru crystallites. Cross-sectional HRTEM of the annealed Ru/C multilayer also shows agglomeration of the Ru layers. Non-specular measurements of the Ru/C multilayers indicate an enhanced uncorrelated roughness upon annealing. The diffuse component in the as-prepared and annealed RU/B4C multilayers shows insignificant changes. The increase in interfacial roughness in the Ru/C multilayer results from agglomeration of the Ru after annealing, consistent with HRTEM observation.

A Monte Carlo simulation approach has been developed to model transport and film profile evolution for rarefied gas flows during nonplanar CVD over trenches and contact holes. A systematic study of the effect of various parameters on the film conformality including intermolecular collisions, reactant sticking coefficient and feature geometry is reported.

Thin films of TiO2 were grown on SrTiO3 and Al2O3 using Ti(OC3H7)4 in the absence of any external oxygen source such as H2O or O2. On SrTiO3 (001), epitaxial anatase (001) formed even at temperatures (800 °C) above the anatase to rutile phase transition temperature. In situ reflection high energy electron diffraction (RHEED) was used to monitor structural evolution during growth, and the films were further characterized by Auger electron spectroscopy (AES), transmission electron microscopy (TEM), and x-ray diffraction. Reaction kinetics were monitored using mass spectrometry, and these results, combined with temperature-programmed reaction spectroscopy, gave some insight into the deposition process.

The amorphous crystalline transition temperature for Si MBE growth is higher for [111] growth than for [100] growth. The mechanism for the growth of amorphous Si in [111] growth is thought to be due to the possibility of of direct formation of stacking faults on the [111] surface. To investigate this mechanism, a kinetic model describing the amorphous-crystalline transition in low temperature Si [111] MBE growth is proposed. The model allows Si atoms to incorporate at three types of sites: A, B and C where A is the triply covalent bonded correct diamond site, B is the triply covalent bonded wrong hep site and C is the singly covalent bonded wrong site. The model allows for the migration of atoms from a wrong site to a nearest neighbor correct site through Arrhenius type rate equations. The migration from B → A is assumed 1000 times weaker than the reverse migration process. Similarly migrations from C → A are assumed 106 time stronger than the reverse migration. All possible migrations are considered with different rates. At the high temperature, the model will allow the growth of a perfect diamond cubic structure with correct ordering of layers AaBbCc etc. A stochastic model describing the above kinetic model is developed based on the master equation approach and random distribution approximation. The low temperature MBE growth of Si [111] is investigated using this model. The results of the model are compared with existing experimental work [1]. The results are in good agreement. The study shows that the kinetics of the site correcting migration process well describes the observed amorphous-crystalline transition in [111] Si MBE growth.

Applying the previously derived “Three-Partial-Rates” model, CVD-Si/Ge-thin film growth and composition is described as influenced by the partial pressures of silane, germane, and hydrogen chloride. The effect of hydrogen carrier gas throughput variation is considered, as well as the density reduction of polycrystalline growth defects by the action of hydrogen chloride and hydrogen.

The interaction of atomic chlorine with Si(100)2×1 surfaces was studied by using chlorine atom beams. The etching reaction of silicon substrates has been observed when chlorine atoms impinged on the chlorinated surface, at substrate temperatures below 600°C. The major desorption product is SiCl2. Studies of the temperature dependence of the reaction showed that the activation energy are 0.08 eV at 0.4 ML and 0.2 eV at 0.8 ML. These extremely low activation energies suggest that the surface reaction is mainly driven by the internal energy of incident atomic chlorine instead of thermal excitation from Si(100) solid surface. Therefore chlorine atoms enter the transition state without equilibrating at the surface prior to the reaction. The reaction strongly depends on the chlorine coverage on the surface. The reaction occurred above 0.3 ML. The etching probability of the surface reached a maximum at 0.4 ML, and decreased with increasing coverage.

The chemisorption and photodecomposition of trimethylindium (TMIn) and trimethylgallium (TMGa) on GaAs(100) surfaces have been studied by angle-resolved X-ray photoelectron spectroscopy. The In-C bond cleavage of the adsorbed TMIn was observed when the substrate temperature was raised from 150 K to 300 K. The dissociation generates methyl radicals that react with the substrate Ga species to form the Ga-C bond. The In-C bond is also dissociated by 193 nm laser irradiation of TMIn adsorbed on the GaAs at 150 K. Irradiation at 351 nm caused no change in the X-ray photoelectron spectra since photodissociation is not due to the photoabsorption of the GaAs substrate but the photodecomposition of the adsorbed species. Similar results are observed for TMGa on a GaAs(100) substrate.

Growth kinetics of CVD Al films using TIBA(Tri-IsoButyl-Aluminum) as a source material were investigated. Nucleation activation energy of aluminum on the silicon substrate was determined to be 3.2 eV for the first time in this work. It turned out that selectivity between Si and SiO2 was very sensitive to the substrate temperature during deposition, which could be well explained from the nucleation activation energy derived in this work. It was found that the surface topology of aluminum films could be improved by reduction of nucleation activation energy through pre-treatment of the substrate.

A panel discussion on interface roughness was held at the Fall 1992 Materials Research Society meeting. We present a summary of the results presented by the invited speakers on the application and interpretation of X-ray reflectivity, atomic force microscopy (AFM), scanning tunneling microscopy (STM), photoluminescence and transmission electron microscopy. A transcript of the moderated discussion is provided in the final section.

ABSTRACT:: We have developed a method to separate coherent interfacial interdiffusion from incoherent interfacial roughness by extending an electromagnetic dynamical theory to calculate the reflectivity of a multilayer having an arbitrary interfacial profile with a variable degree of randomness in the repeating layer thicknesses. We find that the intensity of the subsidiary maxima are extremely sensitive to incoherent roughness while the intensity of the Bragg maxima are largely determined by the interfacial electron density profiles. Experimental data are modeled in a manner similar to that used by Warren and Averback to determine domain size of crystallites. We divide the multilayer into coherent domains differing from one another by small deviations from the average layer thicknesses. The diffraction intensity from each of these domains is then added to obtain the experimental pattern. The diffraction spectra of a set of Pt/Co multilayers with similar layer thicknesses but prepared with different sputtering gases illustrates the ability to separate the effects of coherent interdiffusion from incoherent roughness. The extent of incoherent roughness obtained using this model to analyze the diffraction data of these Pt-Co multilayers is in good agreement with TEM and STM results from the same samples. The diffraction patterns could not be simulated with abrupt concentration profiles and the extent of interdiffusion was found to be correlated with the energy of reflected neutrals present during the synthesis of the multilayers.

X-ray reflectivity and diffuse scattering are powerful techniques for the non-destructive determination of the vertical and lateral roughness of external and internal interfaces. The influence of roughness on the reflected and transmitted amplitudes is treated in terms of a model first described by Névot and Croce. The diffuse scattering is described by an improved distorted wave Born approximation. A few examples will demonstrate the possibilities of the techniques.

A single quantum well (SQW) is grown at a high substrate temperature and low growth rate (HTLR growth) in order to reduce interface roughness. The lateral well thickness variation in the SQW is characterized by the cathodolumincscence microscopy. It is clarified that HTLR growth can be applied to make a smooth interface for advanced devices.

We have investigated the interface roughness of single thin InP/InAs quantum wells grown by Chemical Beam Epitaxy. We report results of low temperature photoluminescence and secondary ion mass spectroscopy. The interface roughness is characterized by multiple-line photoluminescence spectra and is very sensitive to parameters such as the growth temperature. Details of the interface roughness are discussed based on the shifts of the excitonic energies observed by photoluminescence.

Angular dependence of grazing incidence x-ray scattering and Ge fluorescence yield were measured for the heterostructures of Si1-xGex/Si and the inverted bilayer Si/Si1-xGex as well as two 10-period superlattices. Interfacial roughness, correlation of height fluctuations between interfaces and Ge density profiles in the multilayers were investigated.

Low-order, monolayer by monolayer (1×1) AlAs/GaAs superlattices grown by MBE using different growth techniques have been studied by X-ray diffractometry. High-resolution multiple-crystal diffractometry was used to study diffraction features near the [004] peaks due to the substrate and epilayers. Using this technique, we have investigated the effect of growth techniques on the strain and tilt of the superlattices. High-resolution X-ray diffraction (HRXRD) results suggest that the sample grown by migration-enhanced epitaxy (MEE) is more highly strained and has more tilt than the same superlattice sample grown using the interrupted growth (IG) technique.

The interface between ZnSe thin films and GaAs substrates is characterized by High Resolution Transmission Electron Microscopy and room temperature Spectroscopic Ellipsometry. The films were grown on (001) GaAs by Molecular Beam Epitaxy. A three-phase model is used in the reduction of the ellipsometric data, from which the presence of a transition layer of Ga2Se3, with a thickness of less than 1 nm, is confirmed. These results corroborate the high resolution transmission electron microscopy images obtained from the same samples.

The polymer blend system of deuterated polystyrene (PSd) and the statistical copolymer poly(styrene-co-para-bromo-styrene) (PBrxS) is partially compatible or incompatible depending on the degree of bromination x. The width of the interface in a bilayer system can thus be controlled in a wide range by an adjustment of x. This is demonstrated in neutron reflectivity experiments where the interfacial width is measured with an accuracy better than lnm. The interface width depends strongly on compatibility as expressed by the Flory-Huggins interaction parameter x- Results are compared with current theories.