Kinetic Model of SiGe Selective Epitaxial Growth using RPCVD Technique

Abstract

Recently, selective epitaxial growth (SEG) of B-doped SiGe layers has been used in recessed source/drain (S/D) of pMOSFETs. The uniaxial induced strain enhances the carrier mobility in the channel. In this work, a detailed model for SEG of SiGe has been developed to predict the growth rate and Ge content of layers in dichlorosilane(DCS)-based epitaxy using a reduced-pressure CVD reactor. The model considers each gas precursor contributions from the gas-phase and the surface. The gas flow and temperature distribution were simulated in the CVD reactor and the results were exerted as input parameters for Maxwell energy distribution. The diffusion of molecules from the gas boundaries was calculated by Fick's law and Langmuir isotherm theory (in non-equilibrium case) was applied to analyze the surface. The pattern dependency of the selective growth was also modeled through an interaction theory between different subdivisions of the chips. Overall, a good agreement between the kinetic model and the experimental data were obtained.

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

“…12 However, for this process it has also been shown that some control of loading effects and pattern dependency can be achieved by adjusting the partial pressure of HCl. 13,14 A CVD deposition on blanket wafers may be described using the classical boundary layer theory. 15 In this theory, a laminar gas stream is flowing over the wafer.…”

Selective epitaxy growth of Si1−xGex layers for MOSFETs and FinFETs

“…The reason for pattern dependency relates to the gas kinetics and non-linear gas consumption over the patterned wafer [17,37,38]. The kinetics of CVD growth can physically be described by classical boundary layer theory assuming a laminar gas flow over the wafer [45].…”

“…The molecules are attracted towards the dangling bonds and are then consumed. The vertical diffusion path of the gas molecules was 10-15 mm for the total pressure of 20-40 torr in an Epsilon CVD reactor [37,39]. In the case of a chip with opening arrays, a virtual volume is established as shown in Fig.…”

“…8. [37] The gas-phase depletion for a patterned substrate occurs both vertically and laterally around a single chip (a depletion volume). Inside the chip depletion volume, there are four different sources of species which contribute to selective epitaxy growth:…”

“…The experimental data for various Ge, Si and HCl partial pressures can be applied in Eq. 11 and the etch rates during SiGe epitaxy can be determined [37]. The activation energy can be extracted from Arrhenius curves and are demonstrated in Fig.…”