ABSTRACT Capacitive micromachined ultrasonic transducers (CMUTs) have prospective clinical applic... more ABSTRACT Capacitive micromachined ultrasonic transducers (CMUTs) have prospective clinical applications in ultrasound diagnostics and therapy. We have modeled, fabricated, and characterized CMUT arrays suitable for intravascular and gastrointestinal use. The elements of the CMUT arrays are connected from the back side of the array by through-silicon-vias (TSVs) with a pitch of 25 μm. In the reported work, the presence of TSVs does not reduce the fill factor of the array. Two different membrane designs were fabricated, resulting in a resonance frequency in air of 35.6 and 41.0 MHz, respectively. The measurements were in good agreement with the simulated performance. The realized devices are promising for the fabrication of a 3D-ready and bio-compatible device, suitable for in vivo ultrasound applications.
ABSTRACT Various electrical properties of self-aligned AlGaAs/GaAs heterostructure field¿effect t... more ABSTRACT Various electrical properties of self-aligned AlGaAs/GaAs heterostructure field¿effect transistors (HEMTs) have been studied by self-consistent ensemble Monte Carlo simulations for gatelengths between 0.1 and 1.0 ¿m, and for different depths of ohmic contacts. The maximum transconductance is found to be only weakly dependent on gate length and contact depth. The output drain conductance and the threshold voltage show pronounced short-channel effects for gate lengths at or below 0.2 ¿m and shallow contacts. With deeper contacts, the short¿channel effects appear at longer gate lengths. The switching times vary with gate length from 1.0 ps at 0.1 ¿m to 5.0 ps at 1.0 ¿m. The observed effects are discussed in terms of simple models.
The 40th European Microwave Conference, Sep 1, 2010
Dielectric properties of a two-layer of PZT/ZrO2 thin film have been characterized up to 50 GHz u... more Dielectric properties of a two-layer of PZT/ZrO2 thin film have been characterized up to 50 GHz using the conformal mapping method. PZT/ZrO2 films are of interest to RF MEMS capacitive shunt switches due to the relatively high dielectric constant. In this measurement, relative dielectric constant values of approximately 120 and 200 were obtained at 50 GHz for the PZT/ZrO2 film
The Sixteenth Annual International Conference on Micro Electro Mechanical Systems, 2003. MEMS-03 Kyoto. IEEE, 2003
... like to thank Vinh Ngoc Le, Paolo Bemardi and Kent Nygaard of Oslo University College for mea... more ... like to thank Vinh Ngoc Le, Paolo Bemardi and Kent Nygaard of Oslo University College for measurements on wafer C. We are very gratehl to Bengt G. Svensson at the University of Oslo for the aid with interpretation of the SIMS results. Many thanks to Ferdinand Mhnle and ...
We have investigated the effect of anodic bonding on silicon oxide by measuring MAS capacitors si... more We have investigated the effect of anodic bonding on silicon oxide by measuring MAS capacitors situated in Pyrex cavities. We used two different cavity depths, giving 1 micron or 200 micron vertical distance between the gate electrode and the Pyrex. After bonding, we found that the flat-band voltage of the capacitors situated in 1 micron deep cavities had shifted towards more negative values. ...
ABSTRACT This paper presents a study on the feasibility of packaging monolithically integrated mi... more ABSTRACT This paper presents a study on the feasibility of packaging monolithically integrated micro electro-mechanical systems (MEMS) by anodic bonding. We measured the concentration of mobile ions (Nm), the effective oxide charge (Neff), and the density of interface traps (Dit) before and after bonding. Metal-oxide-semiconductor (MOS) capacitors were used as test structures. The capacitors were situated outside the glass and within glass cavities. In the cavities, the vertical distance d between the gate electrode and the glass ceiling was either d=2 μm, d=10 μm, or d=200 μm. During anodic bonding, Neff increased with ∼1012 cm−2 in the capacitors situated outside the glass. Within glass cavities, the capacitors with d=2 μm had ΔNeff of about 4×1011 cm−2. For the capacitors with d=10 μm and d=200 μm, the increase was in the 1010 cm−2 range. Dit increased by quantities similar to the increases in Neff, except that lower increases were observed in the capacitors outside the glass. Nm increased with ∼1013 cm−2 in the capacitors situated outside the glass. Within the glass, ΔNm was in the low 1011 cm−2 regime. A protective nitride layer deposited on top of the capacitors retarded the increase in Nm during bonding. The results suggest that the increase in Nm also caused the increases in Neff and Dit in the capacitors situated outside the glass. Within the glass cavities, the increase in Neff and Dit are thought to be due to negative bias-temperature instability (NBTI).
The scaling properties of acoustic gas sensors indicate a design window from tens of micrometers ... more The scaling properties of acoustic gas sensors indicate a design window from tens of micrometers to several millimeters in critical feature size, thus favouring a bulk micromachining approach. The first MEMS implementation using a triple-stack glass-silicon-glass process is reported, with highlighted experimental results from prototype design and processing runs. This technology platform is believed to generate new application opportunities within the fields of indoor air quality monitoring and control, respiratory diagnostics and monitoring, and automotive climate control.
2009 IEEE/LEOS International Conference on Optical MEMS and Nanophotonics, 2009
An optical MEMS filter for infrared spectroscopy has been designed, fabricated, and tested. The f... more An optical MEMS filter for infrared spectroscopy has been designed, fabricated, and tested. The filter is a deformable hologram which combines focusing and optical filtering into one element. By modulating sections of the hologram, transmission spectra adapted to the absorption lines of a gas can be generated, allowing accurate measurements of gas concentration. The device is fabricated by micromachining grooves
2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC), 2009
... The 5 μm wide trenches are 290 μm deep, giving an aspect ratio of 58:1. ... Instr. and Meth. ... more ... The 5 μm wide trenches are 290 μm deep, giving an aspect ratio of 58:1. ... Instr. and Meth. A565 (2006) 272 [12] S. Parker, CJ Kenney, D. Gnani, AC Thompson, E. Mandelli, G. Meddeler, J. Hasi, J. Morse, EM Westbrook, IEEE Trans. Nucl. Sci. ...
2011 IEEE International Ultrasonics Symposium, 2011
ABSTRACT This paper presents the fabrication and characterization of a 1-3 silicon-polymer compos... more ABSTRACT This paper presents the fabrication and characterization of a 1-3 silicon-polymer composite matching layer made by Deep Reactive Ion Etch (DRIE) method. A well-defined composite layer thickness of 83 μm was obtained by using Silicon-on-Insulator (SOI) wafers as substrate. The resulting composite has 7 μm size posts and 9 μm spacing between posts. A slight tapering of the posts was observed after the DRIE process, causing the posts to be narrower in the bottom than at the top. The composite was used as acoustic matching layer in an air-backed 15 MHz transducer and characterized by electrical impedance measurements in air. The effective acoustic properties of the composite, speed of sound and acoustic impedance, deduced from measured results, were found to be lower than those predicted from iso-strain model. This deviation can be explained by tapering of the trench walls and the dispersion caused by the finite dimensions of the bi-phase material, an explanation that was verified by FEM simulations.
ABSTRACT Low energy electrons, alpha particles and X-rays has a short penetration depth in silico... more ABSTRACT Low energy electrons, alpha particles and X-rays has a short penetration depth in silicon. For detection of these types of radiation it is important that the detector has a shallow inactive region at the side which is irradiated. A series of shallow dead layer test detectors produced by n-side implantation of phosphorus, arsenic or antimony has been characterized. Leakage current levels in the range 2-5 nA/cm2 were achieved with dead layers in the range 0.1-0.2 μm. A silicon pixel detector which will be used in a hybrid photon detector has been produced with thin dead layer technology. The lower detection limit for electrons with this detector is 2.5 keV
2010 IEEE International Ultrasonics Symposium, 2010
Abstract We have used micromachining methods taken from the MEMS industry to fabricate acoustic m... more Abstract We have used micromachining methods taken from the MEMS industry to fabricate acoustic matching layers for high frequency transducers. The matching layers are made as silicon-polymer composites, with acoustic impedance determined by the ratio between the ...
2012 IEEE International Ultrasonics Symposium, 2012
ABSTRACT This paper presents modeling and characterization of a 2-2 silicon-epoxy composite used ... more ABSTRACT This paper presents modeling and characterization of a 2-2 silicon-epoxy composite used as matching layer for high frequency transducers. The composite was fabricated using Deep Reactive Ion Etching (DRIE), common in the MEMS industry, to form deep trenches into a silicon wafer, and fill them with epoxy resin. This composite was used as acoustic matching layer in an air-backed 15 MHz transducer and characterized by electrical impedance measurements in air. The effective acoustic properties of the composite, i.e., speed of sound, acoustic impedance and mechanical loss tangent, were deduced from the measured electrical impedances. The estimated parameters were compared with results from analytical and FEM models. The models show that the first lateral resonance in the silicon-epoxy 2-2 composite is primarily defined by the composite period, not by the epoxy kerf, and no switching between the two lowest modes is seen near the “interaction zone” in the dispersion curves, where the two lowest branches are close to each other. Higher loss was also observed in coarser composite structures, probably due to dispersion. The simulation results were verified by pulse-echo measurements on two transducers with the composite matching layer period 20 μm and 40 μm, which are just below and just above the interaction zone. The measurements show good agreement with the theoretical calculations.
ABSTRACT Capacitive micromachined ultrasonic transducers (CMUTs) have prospective clinical applic... more ABSTRACT Capacitive micromachined ultrasonic transducers (CMUTs) have prospective clinical applications in ultrasound diagnostics and therapy. We have modeled, fabricated, and characterized CMUT arrays suitable for intravascular and gastrointestinal use. The elements of the CMUT arrays are connected from the back side of the array by through-silicon-vias (TSVs) with a pitch of 25 μm. In the reported work, the presence of TSVs does not reduce the fill factor of the array. Two different membrane designs were fabricated, resulting in a resonance frequency in air of 35.6 and 41.0 MHz, respectively. The measurements were in good agreement with the simulated performance. The realized devices are promising for the fabrication of a 3D-ready and bio-compatible device, suitable for in vivo ultrasound applications.
ABSTRACT Various electrical properties of self-aligned AlGaAs/GaAs heterostructure field¿effect t... more ABSTRACT Various electrical properties of self-aligned AlGaAs/GaAs heterostructure field¿effect transistors (HEMTs) have been studied by self-consistent ensemble Monte Carlo simulations for gatelengths between 0.1 and 1.0 ¿m, and for different depths of ohmic contacts. The maximum transconductance is found to be only weakly dependent on gate length and contact depth. The output drain conductance and the threshold voltage show pronounced short-channel effects for gate lengths at or below 0.2 ¿m and shallow contacts. With deeper contacts, the short¿channel effects appear at longer gate lengths. The switching times vary with gate length from 1.0 ps at 0.1 ¿m to 5.0 ps at 1.0 ¿m. The observed effects are discussed in terms of simple models.
The 40th European Microwave Conference, Sep 1, 2010
Dielectric properties of a two-layer of PZT/ZrO2 thin film have been characterized up to 50 GHz u... more Dielectric properties of a two-layer of PZT/ZrO2 thin film have been characterized up to 50 GHz using the conformal mapping method. PZT/ZrO2 films are of interest to RF MEMS capacitive shunt switches due to the relatively high dielectric constant. In this measurement, relative dielectric constant values of approximately 120 and 200 were obtained at 50 GHz for the PZT/ZrO2 film
The Sixteenth Annual International Conference on Micro Electro Mechanical Systems, 2003. MEMS-03 Kyoto. IEEE, 2003
... like to thank Vinh Ngoc Le, Paolo Bemardi and Kent Nygaard of Oslo University College for mea... more ... like to thank Vinh Ngoc Le, Paolo Bemardi and Kent Nygaard of Oslo University College for measurements on wafer C. We are very gratehl to Bengt G. Svensson at the University of Oslo for the aid with interpretation of the SIMS results. Many thanks to Ferdinand Mhnle and ...
We have investigated the effect of anodic bonding on silicon oxide by measuring MAS capacitors si... more We have investigated the effect of anodic bonding on silicon oxide by measuring MAS capacitors situated in Pyrex cavities. We used two different cavity depths, giving 1 micron or 200 micron vertical distance between the gate electrode and the Pyrex. After bonding, we found that the flat-band voltage of the capacitors situated in 1 micron deep cavities had shifted towards more negative values. ...
ABSTRACT This paper presents a study on the feasibility of packaging monolithically integrated mi... more ABSTRACT This paper presents a study on the feasibility of packaging monolithically integrated micro electro-mechanical systems (MEMS) by anodic bonding. We measured the concentration of mobile ions (Nm), the effective oxide charge (Neff), and the density of interface traps (Dit) before and after bonding. Metal-oxide-semiconductor (MOS) capacitors were used as test structures. The capacitors were situated outside the glass and within glass cavities. In the cavities, the vertical distance d between the gate electrode and the glass ceiling was either d=2 μm, d=10 μm, or d=200 μm. During anodic bonding, Neff increased with ∼1012 cm−2 in the capacitors situated outside the glass. Within glass cavities, the capacitors with d=2 μm had ΔNeff of about 4×1011 cm−2. For the capacitors with d=10 μm and d=200 μm, the increase was in the 1010 cm−2 range. Dit increased by quantities similar to the increases in Neff, except that lower increases were observed in the capacitors outside the glass. Nm increased with ∼1013 cm−2 in the capacitors situated outside the glass. Within the glass, ΔNm was in the low 1011 cm−2 regime. A protective nitride layer deposited on top of the capacitors retarded the increase in Nm during bonding. The results suggest that the increase in Nm also caused the increases in Neff and Dit in the capacitors situated outside the glass. Within the glass cavities, the increase in Neff and Dit are thought to be due to negative bias-temperature instability (NBTI).
The scaling properties of acoustic gas sensors indicate a design window from tens of micrometers ... more The scaling properties of acoustic gas sensors indicate a design window from tens of micrometers to several millimeters in critical feature size, thus favouring a bulk micromachining approach. The first MEMS implementation using a triple-stack glass-silicon-glass process is reported, with highlighted experimental results from prototype design and processing runs. This technology platform is believed to generate new application opportunities within the fields of indoor air quality monitoring and control, respiratory diagnostics and monitoring, and automotive climate control.
2009 IEEE/LEOS International Conference on Optical MEMS and Nanophotonics, 2009
An optical MEMS filter for infrared spectroscopy has been designed, fabricated, and tested. The f... more An optical MEMS filter for infrared spectroscopy has been designed, fabricated, and tested. The filter is a deformable hologram which combines focusing and optical filtering into one element. By modulating sections of the hologram, transmission spectra adapted to the absorption lines of a gas can be generated, allowing accurate measurements of gas concentration. The device is fabricated by micromachining grooves
2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC), 2009
... The 5 μm wide trenches are 290 μm deep, giving an aspect ratio of 58:1. ... Instr. and Meth. ... more ... The 5 μm wide trenches are 290 μm deep, giving an aspect ratio of 58:1. ... Instr. and Meth. A565 (2006) 272 [12] S. Parker, CJ Kenney, D. Gnani, AC Thompson, E. Mandelli, G. Meddeler, J. Hasi, J. Morse, EM Westbrook, IEEE Trans. Nucl. Sci. ...
2011 IEEE International Ultrasonics Symposium, 2011
ABSTRACT This paper presents the fabrication and characterization of a 1-3 silicon-polymer compos... more ABSTRACT This paper presents the fabrication and characterization of a 1-3 silicon-polymer composite matching layer made by Deep Reactive Ion Etch (DRIE) method. A well-defined composite layer thickness of 83 μm was obtained by using Silicon-on-Insulator (SOI) wafers as substrate. The resulting composite has 7 μm size posts and 9 μm spacing between posts. A slight tapering of the posts was observed after the DRIE process, causing the posts to be narrower in the bottom than at the top. The composite was used as acoustic matching layer in an air-backed 15 MHz transducer and characterized by electrical impedance measurements in air. The effective acoustic properties of the composite, speed of sound and acoustic impedance, deduced from measured results, were found to be lower than those predicted from iso-strain model. This deviation can be explained by tapering of the trench walls and the dispersion caused by the finite dimensions of the bi-phase material, an explanation that was verified by FEM simulations.
ABSTRACT Low energy electrons, alpha particles and X-rays has a short penetration depth in silico... more ABSTRACT Low energy electrons, alpha particles and X-rays has a short penetration depth in silicon. For detection of these types of radiation it is important that the detector has a shallow inactive region at the side which is irradiated. A series of shallow dead layer test detectors produced by n-side implantation of phosphorus, arsenic or antimony has been characterized. Leakage current levels in the range 2-5 nA/cm2 were achieved with dead layers in the range 0.1-0.2 μm. A silicon pixel detector which will be used in a hybrid photon detector has been produced with thin dead layer technology. The lower detection limit for electrons with this detector is 2.5 keV
2010 IEEE International Ultrasonics Symposium, 2010
Abstract We have used micromachining methods taken from the MEMS industry to fabricate acoustic m... more Abstract We have used micromachining methods taken from the MEMS industry to fabricate acoustic matching layers for high frequency transducers. The matching layers are made as silicon-polymer composites, with acoustic impedance determined by the ratio between the ...
2012 IEEE International Ultrasonics Symposium, 2012
ABSTRACT This paper presents modeling and characterization of a 2-2 silicon-epoxy composite used ... more ABSTRACT This paper presents modeling and characterization of a 2-2 silicon-epoxy composite used as matching layer for high frequency transducers. The composite was fabricated using Deep Reactive Ion Etching (DRIE), common in the MEMS industry, to form deep trenches into a silicon wafer, and fill them with epoxy resin. This composite was used as acoustic matching layer in an air-backed 15 MHz transducer and characterized by electrical impedance measurements in air. The effective acoustic properties of the composite, i.e., speed of sound, acoustic impedance and mechanical loss tangent, were deduced from the measured electrical impedances. The estimated parameters were compared with results from analytical and FEM models. The models show that the first lateral resonance in the silicon-epoxy 2-2 composite is primarily defined by the composite period, not by the epoxy kerf, and no switching between the two lowest modes is seen near the “interaction zone” in the dispersion curves, where the two lowest branches are close to each other. Higher loss was also observed in coarser composite structures, probably due to dispersion. The simulation results were verified by pulse-echo measurements on two transducers with the composite matching layer period 20 μm and 40 μm, which are just below and just above the interaction zone. The measurements show good agreement with the theoretical calculations.
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Papers by Geir Jensen