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Papers by tommi riekkinen
A fabrication method for parallel-plate structures and a parallel-plate structure arrangement, wh... more A fabrication method for parallel-plate structures and a parallel-plate structure arrangement, wherein the structures have a middle layer, grown on a substrate and disposed between top and bottom electrode layers, wherein the middle layer and the top and bottom electrode layers are deposited on a bottom substrate, and wherein the middle layer is grown first and the top and bottom electrodes are essentially deposited afterwards.
ABSTRACT Epitaxial GaAs material shows a great potential in X-ray spectroscopy and radiography ap... more ABSTRACT Epitaxial GaAs material shows a great potential in X-ray spectroscopy and radiography applications due to its high absorption efficiency and low defect density. Fabrication of pixel radiation detectors from high-purtity epitaxial GaAs has been developed further. The process is based on mesa etching for pixellisation and sputtering for metallization. The leakage currents of processed pad detectors are below 10 nA/cm(2) at a reverse bias of 100V and decrease exponentially with the temperature. Measurement with transient current technique (TCT) shows that electrons have a trapping time of 8 ns. Good spectroscopic result were obtained from both a pad detector and a hybridized Medipix GaAs detector.
Bridging the Micro and Nano Worlds, 2015
Journal of Physics: Condensed Matter, 2015
2007 IEEE Ultrasonics Symposium Proceedings, 2007
... The mode shape can be approximated by X(x, t) = X0(t) sin (πx/L) , where x denotes the positi... more ... The mode shape can be approximated by X(x, t) = X0(t) sin (πx/L) , where x denotes the position along the resonator arm, and X0 is the resonator endpoint displacement. ... The beam dimensions are L × w × h, and the piezolayer size is Lpz × wpz × hpz. ...
Journal of Physics: Condensed Matter, 2015
Microelectronic Engineering, 2002
2014 IEEE International Ultrasonics Symposium, 2014
2008 IEEE Ultrasonics Symposium, 2008
We report on the design, fabrication and characterization of piezoelectrically actuated single-cr... more We report on the design, fabrication and characterization of piezoelectrically actuated single-crystal silicon plate resonators vibrating mainly in their bulk acoustic wave modes. Two resonator types are presented: one operates in the square extensional mode at 26 MHz with Q~18000 and motional resistance Rm~0.240 kOmega, while the other resonator features a resonance at 22 MHz with Q~51000 and Rm~1.5 kOmega.
2008 IEEE Ultrasonics Symposium, 2008
We report on piezoelectrically actuated 13 MHz silicon beam resonators operating in the fundament... more We report on piezoelectrically actuated 13 MHz silicon beam resonators operating in the fundamental length extensional BAW mode. The resonance is evoked using an aluminum nitride layer grown on top of the resonator. We demonstrate quality factors as high as Q~55000 in vacuum, and transduction factors of the order of eta~20 muN=V. The anchor loss is studied using designs with
2011 International Electron Devices Meeting, 2011
Thin Solid Films, 2009
The growth of high-quality AlN films has been studied by reactive sputtering onto Mo electrodes w... more The growth of high-quality AlN films has been studied by reactive sputtering onto Mo electrodes with Ni, Ti, and TiW seed layers and subsequent integration into thin film bulk acoustic wave resonators. The crystalline structure and morphology of the Mo and c-axis oriented AlN ...
Microelectronic Engineering, 2003
ABSTRACT The aim of this work was to develop a deposition process for a high-dielectric constant ... more ABSTRACT The aim of this work was to develop a deposition process for a high-dielectric constant tantalum pentoxide for integrated capacitors. Thin films were deposited reactively on glass wafers using a radio-frequency magnetron sputtering cluster tool at 4 1 various O /Ar flow ratios. By using 2 MeV He backscattering spectroscopy and X-ray diffraction, the films obtained 2 showed a stoichiometric orthorhombic b-Ta O phase at 20% O in the sputtering gas flow. With low-frequency 2 5 2 2 measurements (f 5 100 kHz), a 2003200-mm square metal–insulator–metal (MIM) capacitor with copper electrodes and a 2 340-nm thick dielectric gave a capacitance density of 0.066 mF / cm , with a quality factor (Q) of 650. The value of the relative permittivity) was approximately 25 determined from MIM capacitors of various sizes. The surface roughness of r 2 the 376-nm thick oxide film was found to be small: 0.255 nm. The largest measured capacitor (2003200 mm) gave reasonable results at low frequencies. When the frequency was increased (100 kHz–20 GHz) only for the smaller capacitors 2 (30330 mm) the capacitance remained constant. However, the Q values decreased of the smaller capacitors as a function of frequency. Processed tantalum pentoxide MIM capacitors possessed reasonable electrical properties below 2 GHz and good potential for further improvement. 2003 Published by Elsevier B.V.
Microelectronic Engineering, 2002
A fabrication method for parallel-plate structures and a parallel-plate structure arrangement, wh... more A fabrication method for parallel-plate structures and a parallel-plate structure arrangement, wherein the structures have a middle layer, grown on a substrate and disposed between top and bottom electrode layers, wherein the middle layer and the top and bottom electrode layers are deposited on a bottom substrate, and wherein the middle layer is grown first and the top and bottom electrodes are essentially deposited afterwards.
ABSTRACT Epitaxial GaAs material shows a great potential in X-ray spectroscopy and radiography ap... more ABSTRACT Epitaxial GaAs material shows a great potential in X-ray spectroscopy and radiography applications due to its high absorption efficiency and low defect density. Fabrication of pixel radiation detectors from high-purtity epitaxial GaAs has been developed further. The process is based on mesa etching for pixellisation and sputtering for metallization. The leakage currents of processed pad detectors are below 10 nA/cm(2) at a reverse bias of 100V and decrease exponentially with the temperature. Measurement with transient current technique (TCT) shows that electrons have a trapping time of 8 ns. Good spectroscopic result were obtained from both a pad detector and a hybridized Medipix GaAs detector.
Bridging the Micro and Nano Worlds, 2015
Journal of Physics: Condensed Matter, 2015
2007 IEEE Ultrasonics Symposium Proceedings, 2007
... The mode shape can be approximated by X(x, t) = X0(t) sin (πx/L) , where x denotes the positi... more ... The mode shape can be approximated by X(x, t) = X0(t) sin (πx/L) , where x denotes the position along the resonator arm, and X0 is the resonator endpoint displacement. ... The beam dimensions are L × w × h, and the piezolayer size is Lpz × wpz × hpz. ...
Journal of Physics: Condensed Matter, 2015
Microelectronic Engineering, 2002
2014 IEEE International Ultrasonics Symposium, 2014
2008 IEEE Ultrasonics Symposium, 2008
We report on the design, fabrication and characterization of piezoelectrically actuated single-cr... more We report on the design, fabrication and characterization of piezoelectrically actuated single-crystal silicon plate resonators vibrating mainly in their bulk acoustic wave modes. Two resonator types are presented: one operates in the square extensional mode at 26 MHz with Q~18000 and motional resistance Rm~0.240 kOmega, while the other resonator features a resonance at 22 MHz with Q~51000 and Rm~1.5 kOmega.
2008 IEEE Ultrasonics Symposium, 2008
We report on piezoelectrically actuated 13 MHz silicon beam resonators operating in the fundament... more We report on piezoelectrically actuated 13 MHz silicon beam resonators operating in the fundamental length extensional BAW mode. The resonance is evoked using an aluminum nitride layer grown on top of the resonator. We demonstrate quality factors as high as Q~55000 in vacuum, and transduction factors of the order of eta~20 muN=V. The anchor loss is studied using designs with
2011 International Electron Devices Meeting, 2011
Thin Solid Films, 2009
The growth of high-quality AlN films has been studied by reactive sputtering onto Mo electrodes w... more The growth of high-quality AlN films has been studied by reactive sputtering onto Mo electrodes with Ni, Ti, and TiW seed layers and subsequent integration into thin film bulk acoustic wave resonators. The crystalline structure and morphology of the Mo and c-axis oriented AlN ...
Microelectronic Engineering, 2003
ABSTRACT The aim of this work was to develop a deposition process for a high-dielectric constant ... more ABSTRACT The aim of this work was to develop a deposition process for a high-dielectric constant tantalum pentoxide for integrated capacitors. Thin films were deposited reactively on glass wafers using a radio-frequency magnetron sputtering cluster tool at 4 1 various O /Ar flow ratios. By using 2 MeV He backscattering spectroscopy and X-ray diffraction, the films obtained 2 showed a stoichiometric orthorhombic b-Ta O phase at 20% O in the sputtering gas flow. With low-frequency 2 5 2 2 measurements (f 5 100 kHz), a 2003200-mm square metal–insulator–metal (MIM) capacitor with copper electrodes and a 2 340-nm thick dielectric gave a capacitance density of 0.066 mF / cm , with a quality factor (Q) of 650. The value of the relative permittivity) was approximately 25 determined from MIM capacitors of various sizes. The surface roughness of r 2 the 376-nm thick oxide film was found to be small: 0.255 nm. The largest measured capacitor (2003200 mm) gave reasonable results at low frequencies. When the frequency was increased (100 kHz–20 GHz) only for the smaller capacitors 2 (30330 mm) the capacitance remained constant. However, the Q values decreased of the smaller capacitors as a function of frequency. Processed tantalum pentoxide MIM capacitors possessed reasonable electrical properties below 2 GHz and good potential for further improvement. 2003 Published by Elsevier B.V.
Microelectronic Engineering, 2002