Epitaxial oxide thin films on Si(001)

Abstract

Over the years, the development of epitaxial oxides on silicon has been a great technological challenge. Amorphous silicon oxide layer forms quickly at the interface when the Si surface is exposed to oxygen, making the intended oxide heteroepitaxy on Si substrate extremely difficult. Epitaxial oxides such as BaTiO3 (BTO) and SrTiO3 (STO) integrated with Si are highly desirable for future generation transistor gate dielectric and ferroelectric memory cell applications. In this article, we review the recent progress in the heteroepitaxy of oxide thin films on Si(001) substrate by using the molecular beam epitaxy technique at Motorola Labs. Structural, interfacial and electrical properties of the oxide thin films on Si have been characterized using in situ reflection high energy electron diffraction, x-ray diffraction, spectroscopic ellipsometry, atomic force microscopy, Auger electron spectroscopy, x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, high-resolution transmission electron energy loss spectroscopy, capacitance–voltage and current–voltage measurement. We also present the transistor results and address the impact of the epitaxial oxide films on future generation metal-oxide-semiconductor field effect transistors.

Epitaxial growth of yttrium-stabilized HfO2 high-k gate dielectric thin films on Si

“…It is well known that epitaxial growth of metal oxide films on Si is a great technical challenge due to the easily formed amorphous silicon oxide layer on Si surface in an oxygen atmosphere preventing the intended oxide heteroepitaxy on Si substrate. 8 Nevertheless, epitaxial growth of yttrium-stabilized ZrO 2 ͑YSZ͒ and SrTiO 3 high-k gate dielectrics on bare Si has been successfully demonstrated. [9][10][11] However, to the best of our knowledge, there is no report of epitaxial HfO 2 on bare Si.…”

Interfacial reaction in the growth of epitaxial SrTiO3 thin films on (001) Si substrates

“…Since then, many groups have achieved epitaxial growth of SrTiO 3 on silicon using very different growth strategies. 3,4,18,19,[25][26][27] Even when epitaxial overgrowth of SrTiO 3 on silicon is achieved, however, a reaction might occur below the growing surface at the SrTiO 3 / Si interface, as is well known to occur in other epitaxial systems with unstable interfaces. [28][29][30][31][32] In the present work, we investigate the dependence of the SrTiO 3 / Si interface reaction on the flux ratio of Sr/ Ti and on the pretreatment of the silicon substrate surface.…”

“…In the specific case of SrTiO 3 , processing temperatures of ϳ600°C are used to achieve epitaxial SrTiO 3 films on ͑001͒ Si. 3,4,6,7,18,19 As interfacial reactions can lead to unwanted interfacial reaction layers with low permittivity that would degrade the device performance, the growth of films must be achieved through special reaction paths which can be provided by molecular-beam epitaxy ͑MBE͒. Initially, SrTiO 3 thin films were grown on ͑001͒ Si using a thick SrO buffer layer typically 10 nm in thickness.…”

“…[1][2][3][4][5][6][7] In practice, however, it remains a huge challenge to achieve the required electronic properties to make SrTiO 3 a viable gate dielectric for siliconbased MOSFETs. [8][9][10][11][12] The stability, bonding, and microstructure of the interface between the oxide film and the substrate are determined by thermodynamic and kinetic effects.…”

Initial growth stage of a highly mismatched strontium film on a hydrogen-terminated silicon (111) surface

“…The epitaxial growth of SrO films on Si͑100͒ 2 ϫ 1 and ͑111͒ 7 ϫ 7 surfaces with SrSi 2 or SiO 2 interfaces were studied well. [4][5][6][7][8][9] While Sr films on Si͑100͒ 2 ϫ 1 and ͑111͒ 7 ϫ 7 surfaces had amorphous form resulting from a lattice mismatch as large as 12% with Si. If the surface is modified by foreign atoms, the interaction of deposited atoms on Si is strongly affected.…”