Zirconium Oxide Films on Si(100) Bull. Korean Chem. Soc. 2009, Vol. 30, No. 11 2729 Physical and Chemical Investigation of Su bstrate Tem perature Dependence of Zirconium Oxide Films on Si(100) Misun Chun, Myung-Jun Moon, † Juyun Park, and Yong-Cheol Kang * Department of Chemistry, Pukyong National University, Busan 608-737, Korea. * E-mail: yckang@pknu.ac.kr † Department of Industrial Chemistry, Pukyong National University, Busan 606-739, Korea Received July 25, 2009, Accepted October 15, 2009 We report here the surface behavior of zirconium oxide deposited on Si(100) substrate depending on the different substrate temperatures. The zirconium oxide thin films were successfully deposited on the Si(100) surfaces applying radio-frequency (RF) magnetron sputtering process. The obtained zirconium oxide films were characterized by X-ray photoelectron spectroscopy (XPS) for study about the chemical environment of the elements, X-ray diffraction (XRD) for check the crystallinity of the films, spectroscopic ellipsometry (SE) technique for measuring the thickness of the films, and the morphology of the films were investigated by atomic force microscope (AFM). We found that the oxida- tion states of zirconium were changed from zirconium suboxides (ZrOx,y, x,y < 2) (x; higher and y; lower oxidation state of zirconium) to zirconia (ZrO2), and the surface was smoothed as the substrate temperature increased. Key Words: Zirconia, XPS, Oxidation state, RF-sputtering, Thin film Introduction Zirconium oxide is one of the technologically important ma- terials characterized by a high melting point, ionic conductivity, optical properties, good thermal insulating characteristics, high hardness, large resistance against oxidation, high refractive index, and broad region of low absorption from the near-UV to the mid-IR. 1,2 The combination of these properties is attractive for wide range of applications which include laser mirrors, broad band interference filters, and ionic conductors. 3,4 Also, zirco- nium oxide thin film may be used as fuel cells, 5 memory device, 6 heat-resistant materials, 7 optical filters, 8 and sensors. 9 Advantages of zirconia such as its thermal stability with Si substrate and its high dielectric constant make it one of the most promising gate dielectric candidates for SiO2. Unfortunately, they suffer from mobility degradation, fixed charge issues. 10 Fur- thermore, they will crystallize at relatively low temperature, leading to the formation of grain boundaries. 10-12 Zirconium oxide thin films have been widely deposited by various deposition techniques including electron-beam deposi- tion, 13 chemical vapor deposition (CVD), 14 reactive sputtering, 9 radio frequency, direct current reactive magnetron sputtering, 15 and ion beam sputtering deposition. 16 Most of zirconium oxide films were prepared by reactive sputtering using metal target. 17 Some zirconia films were deposited by radio frequency (RF) sputtering with a zirconia ceramic target. 18 In the present work, zirconium oxide thin films were depo- sited on p-type Si(100) wafer by RF plasma sputtering from metallic zirconium target in Ar/O2 plasma gas which is mixed with same volume ratio. The resulted films were obtained at different substrate temperatures. Experimental Section Deposition of zirconium oxide. Zirconium oxide films were deposited on p-type Si(100) wafer substrates by reactive RF magnetron sputtering from a metallic zirconium target with a diameter of 50 mm and a thickness of 3 mm. The Si substrates with native oxide were carefully cleaned by known cleaning process 3 before introducing it into the sputtering chamber. The deposition chamber was evacuated using a roughing pump (RP) and a turbo molecular pump (TMP) to 1.0 × 10 -7 Torr of base pre- ssure range. The mixed sputtering gas, Ar (99.99% purity) and O2 (99.99% purity), was introduced into the deposition chamber separately and controlled by standard mass flow controllers. The zirconium target was cleaned by pre-sputtering with an RF po- wer (13.56 MHz) of 20 W for 1 hr with mixed sputter gas while the substrate was shielded in order to remove the surface con- taminants on the zirconium target and stabilize the plasma. In the present work, sputter deposition was performed at di- fferent substrate temperatures with the same RF power of 20 W for 3 hr. The pressure of the sputtering chamber during the RF sputtering process was kept at 45 mTorr as measured by a con- vectron gauge. During the sputtering, the total gases (Ar : O2, 1 : 1 volume ratio) flowing flux was kept at 20 sccm. The zir- conium oxide films were deposited at different substrate tem- peratures i.e. room temperature, 373, 473, 573, and 623 K. Morphology and thickness of the films. The crystal structure of the zirconium oxide thin films deposited on Si(100) wafer was determined by X-ray diffraction (XRD) using a PHILIPS (Netheland) X’Pert-MPD system applying a grazing mode. The used X-ray source was Cu Kα radiation. The scanning angle, 2θ, was varied from 10 o to 80 o with a detection step of 0.02 o . The JCPDS international diffraction data base 19 has been used to indentify the crystalline phase. The surface morphology of zirconium oxide film was inves- tigated using an atomic force microscopy (AFM), a Veeco Mul- timode Digital Instruments Nanoscope IIIα system, in contact mode. The surface roughness was measured as root mean square (RMS) value over the area of 1 µm × 1 µm. The thickness of the zirconium oxide thin films was deduced by spectroscopic ellipsometry (Gaertner L2W830) (SE). The SE