Electrical Properties and Interfacial Studies of HfxTi1–xO2 High Permittivity Gate Insulators Deposited on Germanium Substrates

Materials

Qifeng Lu²  Yifei Mu²  Joseph W. Roberts⁵  Mohammed Althobaiti¹  Vinod R. Dhanak¹  Jingjin Wu²  Chun Zhao³  Ce Zhou Zhao²  Qian Zhang⁴  Li Yang⁴  Ivona Z. Mitrovic²  Stephen Taylor²  Paul R. Chalker⁵ 

[1] Department of Physics, University of Liverpool, Liverpool L69 7ZE, UK;Department of Electrical Engineering and Electronics, University of Liverpool, Liverpool L69 3GJ, UK;Nano and Advanced Materials Institute, Hong Kong University of Science and Technology, Kowloon 999077, Hong Kong, China;Department of Chemistry, Xi’an Jiaotong-Liverpool University, Suzhou 215123, China;Center for Materials and Structures, School of Engineering, University of Liverpool, Liverpool L69 3GH, UK;

关键词: Ge substrate;    titanium-doped hafnium oxide;    XPS;    XRD;    AFM;   

DOI  :  10.3390/ma8125454

来源: mdpi

【 摘 要 】

In this research, the hafnium titanate oxide thin films, Ti_xHf_1–xO₂, with titanium contents of x = 0, 0.25, 0.9, and 1 were deposited on germanium substrates by atomic layer deposition (ALD) at 300 °C. The approximate deposition rates of 0.2 Å and 0.17 Å per cycle were obtained for titanium oxide and hafnium oxide, respectively. X-ray Photoelectron Spectroscopy (XPS) indicates the formation of GeO_x and germanate at the interface. X-ray diffraction (XRD) indicates that all the thin films remain amorphous for this deposition condition. The surface roughness was analyzed using an atomic force microscope (AFM) for each sample. The electrical characterization shows very low hysteresis between ramp up and ramp down of the Capacitance-Voltage (CV) and the curves are indicative of low trap densities. A relatively large leakage current is observed and the lowest leakage current among the four samples is about 1 mA/cm² at a bias of 0.5 V for a Ti_0.9Hf_0.1O₂ sample. The large leakage current is partially attributed to the deterioration of the interface between Ge and Ti_xHf_1–xO₂ caused by the oxidation source from HfO₂. Consideration of the energy band diagrams for the different materials systems also provides a possible explanation for the observed leakage current behavior.

【 授权许可】

CC BY   
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