Low temperature passivation of Si_1−xGe_x alloys by dry high pressure oxidation

Abstract

Thermal passivation of Si_1−xGe_x using high pressure (70 MPa) oxidation was studied for potential use in MOS-device applications. Alloys of CVD-grown Si_1−xGe_x (x = 10 and 15 at.%, 200 and 150 nm thick, respectively), were oxidized at 500 and 550°C using high purity dry oxygen at a pressure of 70 MPa. For comparative purposes, a second set of alloys were oxidized using conventional wet atmospheric pressure oxidation at 800°C. X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, transmission electron microscopy (TEM), and metal-oxide semiconductor capacitance-voltage (C-V) measurements were used to characterize the as-grown oxides. Chemical analysis by XPS confirmed that under high pressure conditions compositionally congruent oxides are grown from these alloys. High resolution TEM and Raman spectroscopy show that the as-grown oxide/semiconductor interface is planar and free of Ge enrichment on a scale of 1-2 monolayers. A midgap interface state density for both the 10 and 15 at.% samples of 1 × 10¹² cm⁻² eV⁻¹ was estimated based on 1 MHz C-V measurement.