Epitaxial Gd2O3 on strained Si1−xGex layers for next generation complementary metal oxide semiconductor device application

Abstract

Strained Si1−xGex (x = 0.1–0.4) layers were grown on Si(111) and Si(001) substrates using molecular beam epitaxy followed by the growth of epitaxial Gd2O3 thin films on Si1−xGex layers using same technique. Pt/Gd2O3/Si1−xGex/Si stacks fabricated by several in situ process steps exhibit excellent electrical properties. Surface and microstructural analysis of both Si1−xGex and Gd2O3 layers carried out by different in situ and ex situ tools reveal a relaxed epi-Gd2O3 layer on a strained Si1−xGex layer on both Si(111) and Si(001) substrates with sharp interfaces between the oxide and the SiGe layer. Standard electrical measurements, such as capacitance-voltage and leakage current analysis, demonstrate promising electrical properties for such metal oxide semiconductor capacitors. A capacitance equivalent thickness as low as 1.20 nm with associated leakage current density of 2.0 mA/cm2 was obtained for devices with 4.5 nm thin oxide films where the density of interface trap (Dit) was only ∼1011 cm−2 eV−1.