Lyndee L. Hilt

Development of high dielectric constant epitaxial oxides on silicon by molecular beam epitaxy

Thin films of perovskite-type oxide SrTiO 3 have been grown epitaxially on Si(001) substrates using molecular beam epitaxy. Using reflection high energy electron diffraction (RHEED) we have determined the optimum growth conditions for these type of oxides directly on silicon. Also, observations of RHEED during growth and X-ray diffraction (XRD) analysis indicate that high quality heteroepitaxy on Si takes place with SrTiO 3 (001)//Si(001) and SrTiO 3 [010]//Si[110]. Thin SrTiO 3 layers grown directly on Si were used as the gate dielectric for the fabrication of MOSFET devices. An effective oxide thickness < 10 A has been obtained for a 110 A thick SrTiO 3 dielectric film with interface state density around 6.4 x 10 10 cm -2 eV -1 , and the inversion layer carrier mobilities of 220 and 62 cm 2 V -1 s -1 for NMOS and PMOS devices, respectively.

Epitaxial oxides on silicon grown by molecular beam epitaxy

Using molecular beam epitaxy, thin films of perovskite-type oxide Sr x Ba 1-x TiO 3 (0 ≤ x ≤ 1) have been grown epitaxially on Si(001) substrates. Growth parameters were determined using reflection high energy electron diffraction (RHEED). Observation of RHEED during growth and X-ray diffraction analysis indicates that high quality heteroepitaxy on Si takes place with Sr x Ba 1-x TiO 3 (001)//Si(001) and Sr x Ba 1-x TiO 3 [010]//Si[110]. Extensive atomic simulations have also been carried out to understand the interface structure and give some insights into the initial growth mechanism of the oxide layers on silicon. SrTiO 3 layers grown directly on Si were used as the gate dielectric for the fabrication of MOSFET devices. An effective oxide thickness < 10 A has been obtained for a 110 A thick SrTiO 3 dielectric film with interface state density around 6.4 x 10 10 /cm 2 /eV, and the inversion layer carrier mobilities of 220 and 62 cm 2 V/s for NMOS and PMOS devices, respectively.