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

Abstract

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.

Quantification of substitutional and interstitial carbon in thin SiGeC films using in-line X-ray-photoelectron spectroscopy

“…The motivations and processes have been described in more detail elsewhere. 21 Briefly, to preferentially incorporate carbon atoms into substitutional position, the growth temperature must be as low as possible while maintaining high growth rates. The Si 2 H 6 precursor leads to significantly higher SiGe growth rates than with SiH 4 for a given germanium composition and growth temperature, due to lower bonding energies.…”