Mechanisms of Polycrystalline Growth of SiGe in Thermal CVD Processes using Si2H6 and GeF4

Abstract

The mechanism of SiGe film growth from Si2H6 and GeF4 was examined by ab initio B3LYP/6-31G** calculations using three cluster surface models. Energies of reaction and activation were calculated, and the process of SiGe film growth was analyzed. It was found that the reaction of GeF4 with Si2H6 formed GeF2 by much lower activation energy than decomposition of GeF4. In addition, GeF2 made activation energy of surface reactions lower than using only Si2H6.

Properties of SiGe Films Fabricated by Reactive Thermal Chemical Vapor Deposition Using Lamp Heating

“…The Si 2 H 6 decomposes to generate silylene, SiH 2 , in the gas phase with a reaction energy of 2.3 eV, which is much smaller than those of GeF 4 decomposition. 18) Therefore, the SiH 2 is likely generated in the gas phase under the present deposition conditions. In addition, exothermic intermolecule reaction between GeF 4 and Si 2 H 6 generates SiH 3 F and GeF 2 with a low activation energy of 1.37 eV.…”

“…In addition, exothermic intermolecule reaction between GeF 4 and Si 2 H 6 generates SiH 3 F and GeF 2 with a low activation energy of 1.37 eV. Thus SiH 3 F and GeF 2 , which is considered to be a key molecule for Ge deposition, 18,19) are also likely generated in the gas phase. Among these reaction products, the activation energies of the surface reaction of SiH 2 and GeF 2 are rather small.…”

“…Thus, the reaction of GeF 4 with the film surface Si-H bond, which generates the Si-F bond, was suppressed with increasing gas phase reaction. 18) Therefore, the F concentration in the SiGe film decreases with increasing gas phase reaction.…”