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Liu, Yiqun

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Liu

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Yiqun

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Liu, Yiqun
Author's Publications: search.filters.isAuthorOfPublication.18eb2161-52ae-4f95-822d-f2589c9a59e8

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    Frequency response of LaAlO3/SrTiO3 all-oxide field-effect transistors
    (Elsevier BV, 2012) Liu, Qingmin; Dong, Lin; Liu, Yiqun; Gordon, Roy; Ye, Peide D.; Fay, Patrick; Seabaugh, Alan
    The frequency response of all oxide field-effect transistors with amorphous LaAlO3 on a crystalline SrTiO3 substrate is reported. The intrinsic cut-off frequencies of 4 μm gate-length devices are found to be approximately 17 MHz indicating that with gate length scaling gigahertz cut-off frequency is possible. The low cut-off frequency is primarily limited by the low effective mobility. The estimated effective mobility value determined from the S-parameter measurement is 3.8 cm2/Vs, which is consistent with previous reports. Small-signal equivalent circuit model parameters are extracted by fitting to on-wafer measured S-parameters. Good agreement is obtained between measured and simulated S-parameters based on the equivalent circuit model.
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    Effects of Low Temperature O2 Treatment on the Electrical Characteristics of Amorphous LaAlO3 Films by Atomic Layer Deposition
    (Electrochemical Society, 2008) Liu, Yiqun; Kim, Hoon; Wang, Jun-Jieh; Li, Huazhi; Gordon, Roy
    Amorphous LaAlO3 films were deposited on hydrogen-terminated silicon substrates by atomic layer deposition (ALD) at 300 oC. The precursors were lanthanum tris(N,N'-diisopropylformamidinate), trimethylaluminum (TMA) and water. Capacitance-voltage measurements made on ALD MoN/LaAlO3/Si stacks showed humps especially at low frequencies. They were effectively removed by O2 treatment at 300 o C without affecting the dielectric constant (kappa~15). The O2 treatment can be carried out either after deposition of a LaAlO3 film, or after each ALD cycle. The O2 treatment also lowered the leakage current from 80 mA cm-2 to 1 mA cm-2 for EOT = 1.3 nm. This indicates that oxygen vacancies are the main defects in as-deposited LaAlO3. Oxygen treated LaAlO3 is one of the best candidates for future high-kappa dielectric material due to its low leakage, low defect density and abrupt interface with silicon.
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    Chemical Vapor Deposition (CVD) of Manganese Self-Aligned Diffusion Barriers for Cu Interconnections in Microelectronics
    (Materials Research Society, 2009) Gordon, Roy; Kim, Hoon; Au, Yeung; Wang, Hongtao; Bhandari, Harish B; Liu, Yiqun; Lee, Don K; Lin, Youbo
    Barriers to prevent diffusion of copper, oxygen and water vapor were formed by CVD using a manganese precursor vapor that reacts with silica surfaces. The manganese metal penetrates only a few nanometers into the silica to make conformal amorphous manganese silicate layers. This MnSixOy was found to be an excellent barrier to the diffusion of Cu, O2 and H2O vapor. The adhesion strength of Cu to the MnSixOy was found to be sufficiently strong to satisfy the semiconductor industry requirements for interconnections in future microelectronic devices. CVD Mn dissolves into copper surfaces and then diffuses to increase adhesion to SiCNO capping layers.