Substitutional Carbon Incorporation in SiGeC/Si Heterostructures: Influence of Silicon Precursors

In this paper, SiGe or SiGeC epitaxy with Silane or Disilane, Germane and Methylsilane precursors was studied in a 300 mm industrial Reduced Pressure-Chemical Vapor Deposition (RP-CVD) reactor. The SiGe growth rate exponentially increased with the temperature in the 500 °C - 600 °C range for both silicon precursors (activation energy Ea = 2.1 eV). It was, at 550 °C, almost twice higher with Si2H6 than with SiH4. At low temperature, Si2H6 is indeed more reactive than SiH4, resulting in SiGe growth rates significantly higher for a given germanium composition. Then, carbon incorporation at 550 °C into Si0.8Ge0.2 was studied. The higher reactivity of Si2H6 compared to SiH4 resulted in a better substitutional carbon incorporation. In our experimental conditions, 1.2 at% of fully substitutional carbon atoms could indeed be obtained with Si2H6 (without any detectable interstitial ones). Meanwhile, only 0.5 at% of fully substitutional carbon atoms was obtained with SiH4.