For about 20 years STR is developing the model of silicon deposition from chlorosilanes (DCS, TCS, STC). The model can be used to simulate single crystalline silicon and 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 analyze the reasons for layer thickness non-uniformity and test different approaches to improve it. Gas injection redistribution between inlet zones, flow rate variation, chamber geometry optimization, improving temperature profile , and other measures can be simulated to find out the effect on deposition rate and layer uniformity.

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

Si Epitaxy in Trenches

Modeling analysis of Si epitaxy has been the latest addition to our Si-based modeling portfolio. It is based on a multiscale approach that accounts for the transport and chemical reactions both in the reactor and in the trenches. In joint publication with On Semiconductor (*) we describe the mechanism of direct or reverse growth starvation (higher growth rate at the trench top or bottom, respectively) and explain the evolution of the trench shape observed in the experiment. This research work facilitated improvement of the thickness uniformity within the trench and across the wafer with the proper choice of process parameters.