Oxide Thin Films and Composites and Related Methods of Deposition ( 99070/99020)
The synthesis of epitaxial functional oxide thin films on silicon is required for large-scale integration of microelectronic, microwave, and optical devices. This invention provides deposition techniques overcoming limitations of the prior art. Metal organic molecular beam epitaxy (MOMBE) is employed for the deposition of nanometer dimension metal oxide thin films of desired composition and morphology on Si, Ge and other substrates. The technology enables the production of a thin highly uniform layer of epitaxial oxide on Si substrates. Subsequent epitaxially deposition of high-temperature-superconducting (HTSC) and ferroelectric (FE) oxide films provides for the construction of a wide range of electronic, optical and photonic devices.
ADVANTAGES: Epitaxial functional oxide thin film deposition on Si is achieved under conditions that employ moderate metal organic precursor heating and avoid amorphous SiO2 formation.
SUMMARY: Deposition of highly crystalline, epitaxial high-temperature-superconducting (HTSC) oxide and ferroelectric (FE) oxide thin films on oxide substrates, such as magnesium oxide (MgO), is necessary in the fabrication of many microelectronic, microwave, and optical devices. A variety of deposition techniques have been used to grow MgO thin films on Si including metal-organic chemical vapor deposition (MOCVD), e-beam-assisted molecular beam epitaxy (MBE) and sol-gel methods. Electron-beam evaporation of MgO onto Si in an oxygen ambient provides the best deposition of epitaxial MgO on Si to date. However, inherent mechanical and process control difficulties using electron-beam sources in an oxygen atmosphere limit use for large area coverage.
This invention overcomes limitations of the prior art. Metal organic molecular beam epitaxy (MOMBE) is employed for the deposition of nanometer dimension (< 50 nm) metal oxide thin films of desired composition and morphology on Si, Ge and other substrates. The process can deposit alkaline earth and rare earth oxides without carbon contamination. Insitu reflection high-energy electron diffraction and other analytical tools permit monitoring of film structural evolution. MOMBE applied at low pressures (~10-5-10-7 torr) with a RF plasma O2 source has been employed to produce 20 - 200 nm epitaxial (100) MgO films on Si (100) substrates. Dielectric properties of deposited MgO films are in agreement with bulk material values. Composite 40 nm MgO /20 nm SiC /Si structures with each of the layers epitaxially oriented in the (100) direction have been constructed with the process. Conditions that employ moderate metal organic precursor heating and avoid amorphous SiO2 formation are achieved. This technology enables the production of a thin highly uniform layer of epitaxial oxide on Si substrates with potential applications in ultra-large scale integration, microelectronic and microphotonic device fabrication.
STATUS: A U. S. Patent has issued as follows. 6,605,151
Bruce W. Wessels, Brent H. Hoerman and Feng Niu
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