Graduation Year

2004

Document Type

Thesis

Degree

M.S.E.E.

Degree Granting Department

Electrical Engineering

Major Professor

Chiou, Y. L.

Keywords

control oxide, conduction mechanism, Poole-Frenkel, hafnium oxide, high-k

Abstract

The scaling of integrated circuits requires the use of alternative dielectric materials as the replacement for silicon dioxide in the submicron devices. The scaling limit for silicon dioxide used in MOSFETs is 1.2nm and the Oxide Nitride Oxide (ONO) stack used in flash memory applications is 13.0nm. The use of alternative dielectrics with high- value will alleviate the problem of charge retention and also would help to decrease the programming voltage in case of flash memory cells. Many alternative high- dielectric materials such as TaO₂, TiO₂, Al₂O₃ etc., have been examined for this purpose previously. Recently the metal oxides such as ZrO₂ and HfO₂ have been found to be viable replacements for the existing oxide.

The high- value along with high bandgap motivates this replacement. A complete modeling of the reactively sputtered HfO₂ films in the thickness range of 294Å to 480Å is attempted using the data obtained by one of the group members at the Sharp Laboratories of America, Inc. The IV and CV data is used to characterize the material properties and conduction mechanism in HfO2 films used as a control dielectric. The slope of the Poole-Frenkel plot is close to the theoretical value in the intermediate region however it starts to deviate at high field regions. Temperature dependent data also suggests that there are two types of traps active in the intermediate and high field regions. However the origin of these traps is not known. Temperature dependent data indicates that there is a rapid increase in the leakage current at elevated temperatures in the high field region further suggesting that the charge retention capability of the device would be adversely affected under such conditions.

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