Impact of Atomic Layer Deposition High k Films on Slow Trap Density in Ge MOS Interfaces With GeOx Interfacial Layers Formed by Plasma Pre-Oxidation

Abstract

For realizing of Ge complementary metal–oxide–semiconductor with a Ge gate stack with thin equivalent oxide thickness, low interface state density ( $\text{D}_{\mathrm{ it}}$ ) and high reliability. In this paper, we examine the slow trap behaviors in the ALD high-k materials including Al2O3, Y2O3, HfO2, and La2O3 on GeOx/Ge interfaces, where the GeOx interfacial layers are formed by plasma pre-oxidation. The C–V curves, $\text{D}_{\mathrm{ it}}$ and slow trap density of the high-k/GeOx/n- and p- Ge MOS capacitors are evaluated and compared. The Ge 3d spectra in X-ray photoemission spectroscopy are also compared among the Al2O3, Y2O3, HfO2, and La2O3 on GeOx/Ge structures. It is found that Al2O3 provides the lowest slow trap density for both electrons and holes in comparison with Y2O3, HfO2, and La2O3 high-k films, while similar $\text{D}_{\mathrm{ it}}$ values are observed among the MOS interfaces with Al2O3, Y2O3, HfO2, and La2O3. The additional slow traps in the MOS capacitors with Y2O3, HfO2, and La2O3 are attributable to any defects in the high-k films and/or the interfaces with GeOx.