Modeling of CVD of Si and SiGe

For modeling of Si epitaxy STR offers CVDSim3D sofware. The tool has capabilities for detailed modeling of temperature distribution, flow, and chemical reactions.

Model of Radiative Heat Transfer

• Heat reflection responsible for redirection of the radiant heat to specific parts of the wafer. Both diffuse and specular reflection is considered.
• Absorption by the semitransparent media (upper and lower quartz dome)
• Refraction at the gas/quartz surfaces redirecting radiant heat from the lamps
• High angular discretization model of radiant heat has been implemented for conjugated simulation of the phenomena listed above

Chemical model of silicon deposition from chlorosilanes (DCS, TCS, STC) can be used to simulate epitaxy of single crystalline silicon as well as polysilicon deposition. The model can be applied to analyze and improve process parameters and design features of commercial CVD reactors (e.g. Centura EPI, ASM Epsilon) or experimental laboratory equipment. Modeling can be used to improve layer thickness and doping uniformity.

Combined, thermal and chemical modeling can be used for optimization of process parameters, gas injection redistribution between inlet zones, flow rate variation, chamber and injector geometry optimization, improving temperature profile, process scaling and transfer.

Simulation can also be useful in developing of new technology. An example of successful use of numerical simulations in the new CVD system development is a cooperation between STR and Bavarian Center for Applied Energy Research [Journal of Crystal Growth (2008) 310(6) 1112-1117]. The system for the epitaxial growth of  silicon  layers on rectangular, large-area substrates of  up to 43 cm x 43 cm was developed. The temperature distribution, the gas  flow, and the distribution of  growth rates were calculated by STR software. The simulated growth rates are in good agreement with experimental  results.

Epitaxy of SiGe

A model of SiGe epitaxial growth from SiH4-GeH4-H2 with account for specific features of surface kinetic mechanism is developed and verified using a wide range of literature and experimental data. It reproduces the major experimental features of SiGe epitaxial growth and helps to interpret observed effects. With the developed model, an analysis of the process in a production scale reactor was carried out successfully and growth characteristics were improved. The model for SiGe CVD can be used to investigate the effect of recipe on the following characteristics:

• SiGe growth rate
• Layer thicknes non-uniformity
• Ge content
• Ge concentration decay length in a Si capping layer