Evaluation of tetrakis(diethylamino)hafnium Precursor in the Formation of Hafnium Oxide Films Using Atomic Layer Deposit
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Evaluation of tetrakis(diethylamino)hafnium Precursor in the Formation of Hafnium Oxide Films Using Atomic Layer Deposition Ronald Inman1, Anand Deshpande1,2, and Gregory Jursich1 1 American Air Liquide Chicago Research Center, 5230 S. East Avenue, Countryside, IL 60514, U.S.A. 2 Department of Chemical Engineering, University of Illinois at Chicago, 810 S. Clinton Street. Chicago, IL 60607, U.S.A. ABSTRACT Due to their compatibility with silicon interface and high dielectric constant, films containing hafnium oxide are becoming strong candidates in replacing silicon oxynitride as the gate dielectric layer in CMOS devices. To achieve ultimate conformality and thickness control, atomic layer deposition is receiving much more attention in recent years for nanometer size film applications. For hafnium oxide deposition by ALD, metal chlorides have traditionally been used as precursors with moisture being the co-reactant; however for gate oxide applications, metal chlorides are not considered suitable due to the corrosive nature of these compounds and the risks of film contamination. Hence, researchers are exploring alternate organometallic precursors in a CVD process with oxygen being the co-reactant. In this work, tetrakis (diethylamino) hafnium precursor is used in an ALD process with moisture co-reactant to deposit hafnium oxide films onto H-terminated Si substrate in a temperature regime of 200 to 350 C. Film composition is determined by x-ray analysis and is found to be stoichiometric without residue from ligand decomposition. Film thickness and uniformity is measured as a function of substrate temperature and reagent pulsing characteristics. These results will be presented and compared with that obtained with the more conventional hafnium chloride precursor. INTRODUCTION As semiconductor design features shrink to sub-100 nm dimension, new materials are needed in order to meet more stringent performance demands. One of the greatest technical challenges today in semiconductor manufacturing is the implementation of new high dielectric materials needed for the gate oxide insulator in CMOS transistors [1]. In recent years, several metal oxides such as HfO2 , ZrO2, Al2O3 along with their silicate and aluminate analogs have been studied as potential candidates.[2-7] Among these different metal oxides, hafnium oxide has received much attention due to its higher resistance and dielectric constant [8,9] and its thermal stability on silicon.[10,11] Thin film deposition of metal oxides such as HfO2 has been achieved by oxidative and hydrolytic reactions with various hafnium precursors both by chemical vapor deposition (CVD) and by atomic layer deposition (ALD). Deposition by oxidation has been done by chemical vapor deposition using tetrakis (diethylamino) hafnium precursor (Hf(DEA)4) and oxygen at relatively high temperatures of 300- 425 C. [12-14] Although good step coverage was obtained, there was typically a few percent of carbon and nitrogen in the film. The majority of thin film HfO2 depositions however were don
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