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

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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 (V\text{o) near the interface between HfO2 and Ge were stabilized by chemically active F. Consequently, the interface state density ($D_{\text{it}}$) 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.
2011-04-25