Chemical Vapor Deposition of ?-Boron Layers on Silicon for Controlled Nanometer-Deep p+n Junction Formation

Nanometer-thick amorphous boron (?-B) layers were formed on (100) Si during exposure to diborane (B2H6) in a chemical vapor deposition (CVD) system, either at atmospheric or reduced pressures, at temperatures down to 500°C. The dependence of the growth mechanism on processing parameters was investigated by analytical techniques, such as transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS), in conjunction with extensive electrical characterization. In particular, devices fabricated by B deposition effectively demonstrated that p + doping of the silicon substrate can be achieved within 10 nm from the surface in a manner that is finely controlled by the B2H6 exposure conditions. High-quality, extremely ultrashallow, p + n junctions were fabricated, and their saturation current was tuned from high Schottky-like values to low deep pn junction-like values by the increasing of the deposited B layer thickness. This junction formation exhibited high selectivity, isotropy, spatial homogeneity, and compatibility with standard Si device fabrication.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc

Pattern Dependency and Loading Effect of Pure-Boron-Layer Chemical-Vapor Deposition

The pattern dependency of pure-boron (PureB) layer chemical-vapor Deposition (CVD) is studied with respect to the correlation between the deposition rate and features like loading effects, deposition parameters and deposition window sizes. It is shown experimentally that the oxide coverage ratio and the size of windows to the Si on patterned wafers are the main parameters affecting the deposition rate. This is correlated to the gas depletion of the reactant species in the stationary/low-velocity boundary layer over the wafer. An estimation of the radius of gas depletion for Si openings and/or diffusion length of diborane in this study yield lengths in the order of centimeters, which is related to the boundary layer thickness. The deposition parameters; pressure and flow rates are optimized to minimize the pattern dependency of the PureB deposition rates. A very low standard deviation, less than 0.02, is achieved while at the same time making it independent of oxide coverage ratios and window sizes.Delft Institute of Microsystems and NanoelectronicsElectrical Engineering, Mathematics and Computer Scienc

Versatile N-Type Profile Engineering by Controlling Arsenic Surface Segregation in Silicon RPCVD

With the purpose of controlling the incorporation of arsenic during RPCVD Si epitaxy, the surface segregation of As during lowtemperature epi growth was investigated. Parameters such as the Si growth rate, As deposition rate and As incorporation rate, which in previous models were either not evaluated or assumed to be constant, were found here to depend on both the As surface coverage and the arsine partial pressure. Knowledge of these dependencies was employed in simultaneous As deposition and Si epi growth to obtain highlycontrollable doping profiles by appropriate variation of the arsine partial pressure.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

Local-Loading Effects for Pure-Boron-Layer Chemical-Vapor Deposition (abstract)

MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

Pattern Dependency of Pure-Boron-Layer Chemical-Vapor Depositions (abstract)

MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

A Kinetic Model for Chemical-Vapor Deposition of Pure-Boron Layers from Diborane (abstract)

MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

Pattern Dependency of Pure-Boron-Layer Chemical-Vapor Depositions

The pattern dependency of pure-boron (PureB) layer chemicalvapor depositions (CVD) is studied with respect to the correlation between the deposition rate and features like loading effects, deposition parameters and deposition window sizes. It is shown experimentally that the oxide coverage ratio and the size of windows to the Si on patterned wafers are the main parameters affecting the deposition rate. This is correlated to the gas depletion of the reactant species in the stationary/low-velocity boundary layer over the wafer. An estimation of the radius of gas depletion for Si openings and/or diffusion length of diborane in this study yields lengths in the order of centimeters, which is related to the boundary layer thickness. The deposition parameters; pressure and flow rates are optimized to minimize the pattern dependency of the PureB deposition rates.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

A Simple Model describing the kinetic of CVD Deposition of Pure-Boron Layers from Diborane

In this paper, an analytical model is established to describe the deposition kinetics and the deposition chamber characteristics that determine the deposition rates of PureB-layers grown by chemicalvapor deposition (CVD) from diborane (B2H6) as gas source on a non-rotating silicon wafer. The model takes into consideration the diffusion mechanism of the diborane species through the stationary boundary layer over the wafer, the gas phase processes and the related surface reactions. This model is based on a wide range of input parameters, such as initial diborane partial pressure, total gas flow, axial position on the wafer, deposition temperature, activation energy of PureB deposition from diborane, surface Hcoverage and reactor dimensions. The model’s predictive capabilities have been verified by experiments performed at 700 ºC in these two different ASM CVD reactors.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

Local-Loading Effects for Pure-Boron-Layer Chemical-Vapor Deposition

The so-called local-loading effect is studied for pure boron (PureB) depositions from B2H6 in a chemical-vapor deposition (CVD) reactor. This effect occurs because the boron is not deposited on oxide and this increases the deposition rate (DR) of boron in open Si areas in the oxide. Experiments are performed for wide range of local-oxide ratio (LOR). Three regions can be distinguished. For LOR 1, the experimental data deviates from the model, showing saturation of DR as the oxide area increases. In this region the gas phase diffusion of the boron atoms across the oxide is limited by their diffusion length. Conditions that allow reliable deposition of 2-nm-thick PureB layers are found.Delft Institute of Microsystems and NanoelectronicsElectrical Engineering, Mathematics and Computer Scienc

Controlled Growth of Non-Uniform Arsenic Profiles in Silicon Reduced-Pressure Chemical Vapor Deposition Epitaxial Layers

An empirical model of As surface segregation during reduced-pressure chemical vapor deposition Si epitaxy is presented. This segregation mechanism determines the resulting doping profile in the grown layer and is here described by a model of simultaneous and independent As adsorption and segregation versus incorporation. The model quantifies this mechanism with enough detail to be successfully applied to the accurate growth of different profiles, including the ascending x ?2 doping profiles. For rapidly descending profiles the segregated As surface layer must be removed, e.g., by ex situ cleaning and Marangoni drying before further Si epitaxy.Microelectronics and Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc