Characteristics of ZrO2 gate dielectric deposited by plasma enhanced atomic layer deposition method

Abstract

Atomic layer deposition (ALD) method is a new deposition technique to improve the combined problems of physical vapor deposition (PVD) and chemical vapor deposition (CVD) methods. Advantages of ALD over other deposition methods are the low impurities content and processing temperature, ultra thin film deposition and excellent thickness uniformity over large substrate areas. Silicon oxide (SiO2), most commonly used as gate oxide, will face the new serious problems such as the thickness limit and high tunneling leakage current as the device dimensions scaled down to the nano-scale level. Zirconium oxide (ZrO2) is considered as one of the alternatives to SiO2 gate dielectric due to the relatively high dielectric constant ( 25), low leakage current and its compatibility with the manufacturing of integrated circuits. In this study, we present the gate dielectric characteristics of ZrO2 deposited by plasma enhanced ALD method. ZrO2 were deposited on p-type Si (100) substrates with and without initial silicon oxide layer at 250 oC using t-butoxide as Zr precursor and oxygen as reactant gas at the total pressure of about 1 Torr. Oxygen reactant gas was introduced both as in normal gas phase and plasma state. Initial silicon oxide layer was grown by in-situ oxygen plasma treatment before ZrO2 deposition at the same processing temperature. All samples were rapid thermal annealed at 800 oC for 10 seconds in nitrogen ambient. The physical and chemical properties were characterized using x-ray diffractometer (XRD), Auger electron microscopy (AES), scanning electron microscope (SEM) and cross-sectional transmission electron microscopy (XTEM). Electrical properties such as leakage current, interface state density and equivalent oxide thickness were calculated using I-V and C-V data.