Thermal oxidation of $Si1−x−yGexCy$ epitaxial layers characterized by Raman and infrared spectroscopies

Thermal dry oxidation of $Si1−x−yGexCy$ epilayers, over a wide range of compositions (⁠$0<x<0.6$ and $0<y<0.05$⁠), is studied to assess the feasibility of its integration into silicon processes. It is found that differing oxidation conditions, with different $x$ and $y$ values, result in measurably different final amounts of Ge segregation and stress in the resultant oxides. Raman and infrared spectroscopies have been used to characterize the influence of oxidation conditions on the oxide and on the epilayer properties. It is found that a linear relationship exists between Raman shifts and C concentration in the epilayer. It is also found that the Raman band related to Si–Si bonds splits into two peaks. This double-peak structure is attributed to the development of a region closest to the oxide/epilayer interfaces which is enriched with Ge due to its rejection from the oxidation front. It is concluded that oxidation temperatures lower than $900°C$ will more readily avoid this segregation, whereas oxidations at higher temperatures, for shorter times, are better suited to minimize the effects of strain generated during the processing.