Improvement in the Property of Field Effect Transistor Having the HfO2/Ge Structure Fabricated by Photoassisted Metal Organic Chemical Vapor Deposition with Fluorine Treatment

Abstract

We have fabricated Ge-based p-channel metal–insulator–semiconductor field effect transistor (p-MISFET) devices using a hafnium oxide (HfO2) gate film prepared by photoassisted metal organic chemical vapor deposition (MOCVD). To reduce the interface state of a HfO2/Ge gate stack, we performed a new F2 treatment method on a Ge surface. Before the deposition of HfO2 insulation thin films on n-type Ge(100), Ge surfaces were treated in fluorine (F2) gas ambient under various conditions. Experimental results show that F is densely distributed at the interface of the HfO2/Ge gate stack with the F2 treatment of the HfO2 bottom layers. Poorly passivated dangling bonds and oxygen vacancies (Vo) near the interface between HfO2 and Ge were stabilized by chemically active F. Consequently, the interface state density (Dit) of the HfO2/Ge gate stack was reduced and the electrical characteristics of the HfO2/Ge p-MISFETs were improved. Therefore, the new F2 treatment method is very useful for fabricating a good HfO2/Ge p-MISFET device.