Atomic layer deposition of crystalline SrHfO3 directly on Ge (001) for high-k dielectric applications

作者：McDaniel Martin D; Hu Chengqing; Lu Sirong; Ngo Thong Q; Posadas Agham; Jiang Aiting; Smith David J; Yu Edward T; Demkov Alexander A; Ekerdt John G^*

来源：Journal of Applied Physics, 2015, 117(5): 054101.

DOI：10.1063/1.4906953

The current work explores the crystalline perovskite oxide, strontium hafnate, as a potential high-k gate dielectric for Ge-based transistors. SrHfO3 (SHO) is grown directly on Ge by atomic layer deposition and becomes crystalline with epitaxial registry after post-deposition vacuum annealing at similar to 700 degrees C for 5min. The 2 x 1 reconstructed, clean Ge (001) surface is a necessary template to achieve crystalline films upon annealing. The SHO films exhibit excellent crystallinity, as shown by x-ray diffraction and transmission electron microscopy. The SHO films have favorable electronic properties for consideration as a high-k gate dielectric on Ge, with satisfactory band offsets (> 2 eV), low leakage current (< 10(-5) A/cm(2) at an applied field of 1 MV/cm) at an equivalent oxide thickness of 1 nm, and a reasonable dielectric constant (k similar to 18). The interface trap density (D-it) is estimated to be as low as similar to 2 x 10(12) cm(-2) eV(-1) under the current growth and anneal conditions. Some interfacial reaction is observed between SHO and Ge at temperatures above similar to 650 degrees C, which may contribute to increased D-it value. This study confirms the potential for crystalline oxides grown directly on Ge by atomic layer deposition for advanced electronic applications.

• 出版日期2015-2-7