dc.description.abstract | With continuous increase in transistor count and clock frequency of semiconductor integrated circuits over the last 50 years following Moore’s Law, the power density of integrated circuits has reached a level that calls for a revolutionary change in transistor technology. Among the proposed solutions, high hole mobility Ge and high electron mobility InGaAs have been considered to be the most promising channel materials for p-channel and n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs), respectively. However, the native oxides of Ge and InGaAs are typically complex in structure and composition, and causes defect states at oxide-semiconductor interface. This study aims at a surface treatment method to resolve the oxides issue and effectively reduce the density of traps (Dit) at high-κ/(Ge, InGaAs) interface.
In addition, a common gate-stack process for Ge and InGaAs devices, consisting of HF cleaning and rapid thermal oxidation (RTO), is developed for fabricating HfO2(4 nm)/Al2O3(1 nm)/(Ge, InGaAs) metal-oxide-semiconductor capacitors (MOSCAPs) by using an atomic layer deposition (ALD) system equipped with a nitrogen plasma source. Typically, the MOSCAPs of Ge and InGaAs prepared by the RTO process show effective capacitance modulation of 66 % and 80 % with interface trap density of 9.4×1011 eV-1cm-2 and 3.9×1011 eV-1cm-2 extracted by conductance method, respectively. Although the capacitance-voltage characteristics of InGaAs MOSCAPs have been improved by the RTO process, the characteristics of Ge ones are not as good as expected.
To improve the performance of aforementioned MOSCAPs, an additional surface treatment by nitrogen plasma is performed before high-κ dielectric deposition. Using the RTO process and nitrogen plasma treatment, the Dit at midgap is reduced to 2.3×1011 eV-1cm-2 and 3.8×1011 eV-1cm-2 for Ge and InGaAs MOSCAP, respectively. As evidenced by x-ray photoelectron spectroscopy, there exist GeONx at high-κ/Ge interface and GaOx and AlN at high-κ/InGaAs interface. The GeONx layer is beneficial for the reliability of Ge devices and the GaOx may play a role of passivating surface defects and dangling bonds. The results of this study are well suited for realizing high performance Ge and InGaAs MOSFETs. | en_US |