Si and SiGe Epitaxy in Perspective

MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

Temperature dependence of chemical-vapor deposition of pure boron layers from diborane

Surface reaction mechanisms are investigated to determine the activation energies of pure boron (PureB) layer deposition at temperatures from 350?°C to 850?°C when using chemical-vapor deposition from diborane in a commercial Si/SiGe epitaxial reactor with either hydrogen or nitrogen as carrier gas. Three distinguishable regions are identified to be related to the dominance of specific chemical reaction mechanisms. Activation energies in H2 are found to be 28?kcal/mol below 400?°C and 6.5?kcal/mol from 400?°C to 700?°C. In N2, the value decreases to 2.1?kcal/mol for all temperatures below 700?°C. The rate of hydrogen desorption is decisive for this behavior.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

An analytical kinetic model for chemical-vapor deposition of pureB 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 pure boron (PureB-) layers grown by chemical-vapor 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 by applying the actual parabolic gas velocity and temperature gradient profiles in the reactor. These are calculated theoretically and also simulated with fluent software. The influence of an axial and lateral diffusion of diborane species and the validity of the model for laminar flow in experimental CVD processes are also treated. 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 H-coverage, and reactor dimensions. By only adjusting these reactor/process parameters, the model was successfully transferred from the ASM Epsilon One to the Epsilon 2000 reactor which has totally different reactor conditions. The model's predictive capabilities have been verified by experiments performed at 700?°C in these two different ASM CVD reactors.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

Ge-on-Si: Single-Crystal Selective Epitaxial Growth in a CVD reactor (abstract)

MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

Ge-on-Si: Single-Crystal Selective Epitaxial Growth in a CVD Reactor

A standard Si/SiGe ASM CVD reactor that was recently modified for merging GaAs and Si epitaxial growth in one system is utilized to achieve intrinsic and doped epitaxial Ge-on-Si with low threading dislocation and defect densities. For this purpose, the system is equipped with 2% diluted GeH4 as the main precursor gas for Ge deposition; and 0.7% diluted AsH3 and B2H6 precursor gases as well as a TriMethylGallium (TMGa) bubbler system for As, B and Ga doping of epitaxial Ge, respectively. The quality of Ge epitaxy on Si is investigated by plan-view and cross-sectional transmission electron-microscopy (TEM) and atomic-force microscopy (AFM) analysis.Delft Institute of Microsystems and NanoelectronicsElectrical 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

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

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

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

MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc