William G. Breiland

Reactive sticking coefficients for silane and disilane on polycrystalline silicon

Reactive sticking coefficients (RSCs) were measured for silane and disilane on polycrystalline silicon for a wide range of temperature and flux (pressure) conditions. The data were obtained from deposition‐rate measurements using molecular beam scattering and a very low‐pressure cold‐wall reactor. The RSCs have nonlinear Arrhenius temperature dependencies and decrease with increasing flux at low (710 °C) temperatures. Several simple models are proposed to explain these observations. The results are compared with previous studies of the SiH4/Si(s) reaction and low‐pressure chemical vapor deposition‐rate measurements.

A virtual interface method for extracting growth rates and high temperature optical constants from thin semiconductor films using in situ normal incidence reflectance

A method is presented in which both optical constants and growth rates may be simultaneously extracted from the in situ normal incidence reflectance of a growing thin film. The method employs a virtual interface model, thus avoiding cumulative errors that are encountered if a standard multiple‐layer model is used. No a priori knowledge of underlying film materials, structures, or locations of interfaces is required. A method to accurately estimate all parameters for starting values in the least‐squares fitting of the data is also presented. This allows one to use a fully automated procedure for extracting information that requires no prior knowledge other than the starting reflectance of the substrate. Monte Carlo simulations are presented to study the ultimate accuracy of the method under ideal conditions for a film structure typical of compound semiconductor growth. Optical constants of GaAs and AlAs at 634 C have been obtained over a wavelength range of 400–990 nm with this method and agree with values...

Improved brightness of 380 nm GaN light emitting diodes through intentional delay of the nucleation island coalescence

Ultraviolet light emitting diodes (LEDs) have been grown using metalorganic vapor phase epitaxy, while monitoring the 550 nm reflected light intensity. During nucleation of GaN on sapphire, the transition from three-dimensional (3D) grain growth to two-dimensional (2D) coalesced growth was intentionally delayed in time by lowering the NH3 flow during the initial high temperature growth. Initially, when the reflectance signal is near zero, the GaN film is rough and composed of partly coalesced 3D grains. Eventually, the reflected light intensity recovers as the 2D morphology evolves. For 380 nm LEDs grown on 3D nucleation layers, we observe increased light output. For LEDs fabricated on GaN films with a longer recovery time an output power of 1.3 mW at 20 mA current was achieved.

Design and Verification of Nearly Ideal Flow and Heat Transfer in a Rotating Disk Chemical Vapor Deposition Reactor

A research chemical vapor deposition reactor design is presented for a rotating disk configuration. The reactor can be operated under conditions such that nearly ideal, one-dimensional, infinite-radius disk behavior is achieved over most of the disk surface. Boundary conditions, flow stability under both isothermal and heated-disk conditions, and gas temperatures are addressed with both one- and two-dimensional numerical fluid mechanics models. In this paper experimental verification of the design using flow visualization and laser Raman thermometry are presented.

Laser studies of the reactivity of SiH with the surface of a depositing film

A new method for studying the interaction of radicals with the surface of a depositing film is presented. This method combines spatially resolved laser spectroscopy with molecular beam techniques and is demonstrated by measuring the state‐resolved reactivity of SiH molecules with the surface of a depositing amorphous hydrogenated silicon film. SiH molecules from a silane glow discharge react at the surface with greater than 0.94 probability. The spatial distribution of the desorbing SiH is consistent with a cosine angular distribution. No dependence of reactivity on rotational state of the SiH was observed.

Comparisons between a gas‐phase model of silane chemical vapor deposition and laser‐diagnostic measurements

Theoretical modeling and experimental measurements have been used to study gas‐phase chemistry in the chemical vapor deposition (CVD) of silicon from silane. Pulsed laser Raman spectroscopy was used to obtain temperature profiles and to obtain absolute density profiles of silane during deposition at atmospheric and 6‐Torr total pressures for temperatures ranging from 500 to 800 °C. Laser‐excited fluorescence was used to obtain relative density profiles of Si2 during deposition at 740 °C in helium with 0–12 Torr added hydrogen. These measurements are compared to predictions from the theoretical model of Coltrin, Kee, and Miller. The predictions agree qualitatively with experiment. These studies indicate that fluid mechanics and gas‐phase chemical kinetics are important considerations in understanding the chemical vapor deposition process.

Observation of HSiCl in a chemical vapor deposition reactor by laser‐excited fluorescence

Using laser‐excited fluorescence, free‐radical HSiCl has been detected in the gas phase during the chemical vapor deposition of silicon from dichlorosilane. Profiles of the relative HSiCl density were measured at atmospheric and low total pressures. Previous studies of chlorosilane deposition have not considered HSiCl as a possible intermediate species. Therefore, its role in the deposition process must be investigated.

In situ spectral reflectance monitoring of III–V epitaxy

Near normal incidence spectral reflectance was used to monitor the growth of ALAs, GaAs, and AlGaAs films by metalorganic chemical vapor deposition in real time. The simultaneous acquisition of reflectance data over a wide spectral bandwidth allows compositional discrimination between layers and greater thickness sensitivity than single wavelength measurements. The potential of this technique for application to device structures was demonstrated by moni-toring the fabrication of AlAs/AlGaAs visible distributed Bragg reflectors.

Gas‐phase silicon atoms in silane chemical vapor deposition: Laser‐excited fluorescence measurements and comparisons with model predictions

Laser‐excited fluorescence was used to detect gas‐phase silicon atoms during chemical vapor deposition from silane. Relative Si densities were measured as a function of height above the susceptor, susceptor temperature, amount of H2 added to the He carrier gas, and total pressure. The Si atom density decreased both upon addition of H2 and as the total pressure was lowered below ∼100 Torr. Comparisons of these measurements with the model developed by Coltrin, Kee, and Miller [J. Electrochem. Soc. 131, 425 (1984)] show that the model predicts the qualitative behavior of the experimental Si atom profiles over a wide range of experimental conditions. Addition of a mechanism for particulate nucleation to the model may resolve some of the discrepancies between model and experiment.

A surface kinetics model for the growth of Si1−xGex films from SiH4/GeH4 mixtures

A model has been developed that semiquantitatively describes the kinetics of Si1−xGex alloy deposition over a wide range of temperatures in the absence of gas‐phase chemistry. The salient feature of the model is that the kinetics of germane and silane deposition are treated as parallel processes, each with an adsorption step in series with a hydrogen desorption step. The two processes are coupled by competition for sites in the adsorption process, and fast equilibration between silicon and germanium hydride on the surface. The model is fit to, and compared with, data available in the recent literature.