Material Properties, Thermal Stabilities and Electrical Characteristics of Ge MOS Devices,Depending on Oxidation States of Ge Oxide: Monoxide GeO(II) and Dioxide GeO2(IV)

摘要

Ge monoxide [GeO(II)] and dioxide [GeO2(IV)], which are selectively formed on Ge substrate bycontrolling pH and redox potential in pretreatment solution, have been confirmed by XPS. △E_C inGeO(II)/Ge and GeO2(IV)/Ge are almost the same, whereas △E_v in GeO(II)/Ge is smaller than thatin GeO2(rV)/Ge, resulting in smaller E_g of GeO(II). GeO(g) desorption is suppressed in LaAlO3/Gegate stack, whereas GeO(g) desorbs through LaAlO3 layer when there is an intentional interfacialGeO(II) layer, leading to a large increase in J_g. GeO(g) desorption temperature in Ge oxide/Ge gatestacks decreases with the increase in the ratio of GeO(II) in Ge oxide and is independent of theoxidation techniques. Since GeO(g) desorption is accompanied by H2O(g) desorption, a new model toexplain the GeO(g) desorption phenomena is proposed, in which Ge(OH)2 decomposes into GeO(g)and H2O(g). Highly effective etching methods of Ge oxide, using HCl solution and HCl vapor at highertemperature than boiling point of Ge (hydro)hloride have been demonstrated.