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Papers by Mitsuhiro Tomita

Research paper thumbnail of 先端ＬＳＩに向けた直接接合極薄ランタンアルミネートゲート絶縁膜

Research paper thumbnail of Improvement in the asymmetric Vfb shift of poly-Si/HfSiON/Si by inserting oxygen diffusion barrier layers into the interfaces

Extended Abstracts of the 2005 International Conference on Solid State Devices and Materials, 2005

Research paper thumbnail of Depth Resolution Parameters and Sputtering Rates Extracted from Amorphous and Crystalline Silicon Materials for SIMS Shallow Depth Profiling

Journal of Surface Analysis, Mar 1, 2005

Research paper thumbnail of Irradiation characteristics of metal-cluster-complex ions containing diverse multi-elements with large mass differences

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007

Tetrairidium dodecacarbonyl, Ir 4 (CO) 12 , is a metal cluster complex which has a molecular weig... more Tetrairidium dodecacarbonyl, Ir 4 (CO) 12 , is a metal cluster complex which has a molecular weight of 1104.9. Using a metal-clustercomplex ion source, the interaction between Ir 4 ðCOÞ þ n ions (n = 0-12) and silicon substrates was studied at a beam energy ranging from 2 keV to 10 keV at normal incidence. By adjusting Wien-filter voltage, the influence of CO ligands was investigated. Experimental results showed that sputtering yield of silicon bombarded with Ir 4 ðCOÞ þ n ions at 10 keV decreased with the number of CO ligands. In the case of 2 keV, deposition tended to be suppressed by removing CO ligands from the impinging cluster ions. The influence of CO ligands was explained by considering changes in surface properties caused by the irradiation of Ir 4 ðCOÞ þ n ions. It was also found that the bombardment with Ir 4 ðCOÞ þ 7 ions at 2.5 keV caused deposition on silicon target.

Research paper thumbnail of Production and Applications of Metal-cluster-complex Ion Beams

Journal of the Vacuum Society of Japan, 2009

A new ion source using massive molecules called metal cluster complexes has been developed. Metal... more A new ion source using massive molecules called metal cluster complexes has been developed. Metal cluster complexes are chemically-synthesized organometallic compounds, which have a wide range of chemical compositions with high molecular weight. The ion source is compact enough to be installed in commonly used secondary ion mass spectrometry (SIMS) systems. Using the ion source, sputtering characteristics of silicon bombarded with normally incident Ir4(CO)7+ ions were investigated. Experimental results showed that the sputtering yield at 10 keV was 36, which is higher than that with Ar+ ions by a factor of 24. In addition, SIMS analyses of boron-delta-doped silicon samples and organic films of poly(methyl methacrylate) (PMMA) were performed. Compared with conventional O2+ ion beams, Ir4(CO)7+ ion beams improved depth resolution by a factor of 2.5 at the same irradiation conditions; the highest depth resolution of 0.9 nm was obtained at 5 keV, 45° with oxygen flooding of 1.3×10-4 Pa. Furthermore, experimental results confirmed that Ir4(CO)7+ ion beams significantly enhanced secondary ion intensity in high-mass region.

Research paper thumbnail of Characteristics of a Metal-Cluster-Complex Ion Beam and Its Application to Secondary Ion Mass Spectrometry (SIMS)

Research paper thumbnail of Influence of thermal diffuse scattering and local stress on the precise measurement of Si1-xGex composition by convergent beam electron diffraction

e-Journal of Surface Science and Nanotechnology

Research paper thumbnail of Depth profiling for ultrashallow implants using backside secondary ion mass spectrometry

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2003

Research paper thumbnail of Laser-assisted atom probe tomography of 15N-enriched nitride thin films for analysis of nitrogen distribution in silicon-based structure

Applied Surface Science, 2015

Research paper thumbnail of Ultra-Thin (EOT ~ 0.31nm) and Low Leakage Dielectrics of La-Aluminate Deposited Directly on Si Substrate

ECS Transactions, 2006

ABSTRACT Ultra-thin (0.31 nm) LaAlO3 gate dielectrics directly deposited on Si substrate were rea... more ABSTRACT Ultra-thin (0.31 nm) LaAlO3 gate dielectrics directly deposited on Si substrate were realized. We found that LaAlO3 deposition at substrate temperature of 700{degree sign}C led to low defect density of the film at the as-deposited state. The electron mobility of LaAlO3 n-MISFET was improved by forming gas annealing, meaning that the defects at the direct interface could be passivated with hydrogen.

Research paper thumbnail of Cryo-Implantation Technology for Controlling Defects and impurity out diffusion

Research paper thumbnail of Contact resistance reduction of Pt-incorporated NiSi for continuous CMOS scaling ∼ Atomic level analysis of Pt/B/As distribution within silicide films &#x223C

2008 IEEE International Electron Devices Meeting, 2008

Platinum (Pt)-incorporation into nickel silicide films is the promising approach to reduce the co... more Platinum (Pt)-incorporation into nickel silicide films is the promising approach to reduce the contact resistance (RC) at silicide/Si interface. Physical properties of Ni1-xPtxSi films were investigated by using local electrode atom probe (LEAP); The distributions of Pt and dopants (such as As and B) were analyzed both at silicide/Si interface and at silicide grain boundary. The silicide grain-size miniaturization was

Research paper thumbnail of Investigation of the factors determining the SIMS depth resolution in silicon-isotope multiple layers

Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures, 2012

In order to identify their controlling factors, the depth resolution parameters for secondary ion... more In order to identify their controlling factors, the depth resolution parameters for secondary ion mass spectrometry, which include the decay length and the standard deviation of the Gaussian function (also referred to as the depth resolution function), for silicon atoms in a silicon matrix with silicon-isotope multiple layers were investigated under oxygen (O þ 2 ) and cesium (Cs þ ) ion bombardments with a wide ion energy range (from 200 eV to 10 keV) and with several incident angles. The use of silicon-isotope multiple layers in this investigation eliminated the chemical segregation effect caused by the sample composition. Measures were also taken to prevent ripple formation on the sputtered sample surface. The obtained depth resolution parameters were proportional to E 1/2 cos h, where E is the primary ion energy per atom and h is the incident angle relative to the surface normal. The relationships for decay length and standard deviation were different for the Cs þ ion, the O þ 2 ion with full oxidization, and the O þ 2 ion without full oxidization. The damage depth was measured by high-resolution Rutherford backscattering spectrometry and it was found that the relationships of the standard deviation versus damage depth depend only on the damage depth with a small dependence on the ion species (O þ 2 =Cs þ ). The degree of mixing near the sputtered surface of thin silicon-isotope multiple layers bombarded by O þ 2 =Cs þ ions was measured using laser-assisted atom probe analysis, and the relationship of the degree of mixing with the depth resolution parameters indicated that the decay length was degraded according to the degree of mixing. Atomic mixing/sputtering simulations revealed the factors determining the depth resolution parameters for secondary ion mass spectrometry. The standard deviation is found to be mainly degraded by the damage depth, which agrees with the results obtained by Rutherford backscattering spectrometry, whereas the decay length is mainly extended by the variance of the damage density profile, which is a parameter of the Gaussian function and governs the degree of mixing near the surface.

Research paper thumbnail of Characteristics of a cluster-ion beam of Os3(CO)n+ (n = 7 or 8) for low-damage sputtering

Surface and Interface Analysis, 2006

Research paper thumbnail of VAMAS round-robin study to evaluate a correction method for saturation effects in D-SIMS

Surface and Interface Analysis, 2014

ABSTRACT Recently, dynamic SIMS (D-SIMS) is being used to analyze ions simultaneously over a wide... more ABSTRACT Recently, dynamic SIMS (D-SIMS) is being used to analyze ions simultaneously over a wide range of concentrations, from matrix level to extremely low (ng g−1). However, D-SIMS detectors, which are mostly used in pulse counting systems, have problems with detector saturation. Thus, the ion intensities of SIMS must be corrected in their high-intensity region. It has been reported that the approximation intermediate extended dead-time model (a-IED model) can be used to correct saturated intensity in the higher region better than can the conventional model. In this study, we evaluated the usefulness of the a-IED model to correct partially saturated and saturated intensities for magnetic-sector-type D-SIMS and quadrupole-type D-SIMS for the effects of dead time. Nine organizations from five countries participated in this project. Analyzed specimens were an arsenic-implanted silicon wafer and a diffused BN onto Si wafer. The instruments used to analyze arsenic-implanted samples were five quadrupole-type SIMS and four magnetic-sector-type SIMS. The instruments used to analyze the BN-diffused samples were three quadrupole-type SIMS, four magnetic-sector-type SIMS, and one time-of-flight-type SIMS. We validated the usefulness of the a-IED model to correct saturated intensities for all SIMS in this round-robin test. The optimum extension parameter ρ tends to be affected by the ratio of the maximum reliable intensity to the maximum intensity. Copyright © 2014 John Wiley & Sons, Ltd.

Research paper thumbnail of Secondary ion yields depending on the primary oxygen ion energy in cameca IMS-4f instrument

Surface and Interface Analysis, 1994

ABSTRACT

Research paper thumbnail of An effect of measurement conditions on the depth resolution for low-energy dual-beam depth profiling using TOF-SIMS

Surface and Interface Analysis, 2013

ABSTRACT An effect of measurement conditions on the depth resolution was investigated for dual-be... more ABSTRACT An effect of measurement conditions on the depth resolution was investigated for dual-beam time of flight-secondary ion mass spectrometry depth profiling of delta-doped-boron multi-layers in silicon with a low-energy sputter ion (200 eV – 2 keV O2+) and with a high-energy primary ion (30 keV Bi+). The depth resolution was evaluated by the intensity ratio of the first peak and the subsequent valley in B+ depth profile for each measurement condition. In the case of sputtering with the low energy of 250 eV, the depth resolution was found to be affected by the damage with the high-energy primary ion (Bi+) and was found to be correlated to the ratio of current density of sputter ion to primary ion. From the depth profiles of implanted Bi+ primary ion remaining at the analysis area, it was proposed that the influence of high-energy primary ion to the depth resolution can be explained with a damage accumulation model. Copyright © 2013 John Wiley & Sons, Ltd.

Research paper thumbnail of Secondary ion mass spectrometry round-robin study of relative sensitivity factors in gallium arsenide

Surface and Interface Analysis, 1998

ABSTRACT

Research paper thumbnail of High-sensitivity x-ray absorption fine structure investigation of arsenic shallow implant in silicon

Spectrochimica Acta Part B: Atomic Spectroscopy, 2009

High-sensitivity fluorescence-yield x-ray absorption fine structure spectroscopy (XAFS) has been ... more High-sensitivity fluorescence-yield x-ray absorption fine structure spectroscopy (XAFS) has been investigated to characterize the local structure around arsenic shallow implant in silicon. Fluorescence-yield XAFS experiments were performed using a high-brilliance synchrotron radiation beam from an in-vacuum-type undulator in a third-generation light source. In addition to investigating the efficiency of high-brilliance undulator x-rays during the fluorescence-yield XAFS measurements, we compared the analytical performance of both the wavelength dispersive spectrometer (WDS) and the energy dispersive spectrometer (EDS) based on the silicon drift detector (SDD). It was confirmed that the WDS reduces the influence of scattering background due to the high spectral resolution. Another advantage of the WDS is high counting rate measurements. It was found that fluorescence-yield XAFS using undulator x-rays combined with the WDS permits superior sensitivity measurements.

Research paper thumbnail of SIMS depth profile study using metal cluster complex ion bombardment

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007

SIMS depth profiles using a metal cluster complex ion of Ir 4 ðCOÞ þ 7 were studied. An unusual i... more SIMS depth profiles using a metal cluster complex ion of Ir 4 ðCOÞ þ 7 were studied. An unusual increase of the sputtering yield under the condition of small incident angle may be attributed to the suppression of taking oxygen from flooding O 2 by the formation of a carbon cover-layer derived from Ir 4 ðCOÞ þ 7 ion. Even though the roughness of the sputtered surface is small, the depth resolution was not improved by decreasing the cluster ion energy to less than 5 keV, because the carbon cover-layer prevents the formation of surface oxide that buffers atomic mixing. To overcome this issue, it will be necessary to eliminate carbon from the cluster ion.

Research paper thumbnail of 先端ＬＳＩに向けた直接接合極薄ランタンアルミネートゲート絶縁膜

Research paper thumbnail of Improvement in the asymmetric Vfb shift of poly-Si/HfSiON/Si by inserting oxygen diffusion barrier layers into the interfaces

Extended Abstracts of the 2005 International Conference on Solid State Devices and Materials, 2005

Research paper thumbnail of Depth Resolution Parameters and Sputtering Rates Extracted from Amorphous and Crystalline Silicon Materials for SIMS Shallow Depth Profiling

Journal of Surface Analysis, Mar 1, 2005

Research paper thumbnail of Irradiation characteristics of metal-cluster-complex ions containing diverse multi-elements with large mass differences

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007

Tetrairidium dodecacarbonyl, Ir 4 (CO) 12 , is a metal cluster complex which has a molecular weig... more Tetrairidium dodecacarbonyl, Ir 4 (CO) 12 , is a metal cluster complex which has a molecular weight of 1104.9. Using a metal-clustercomplex ion source, the interaction between Ir 4 ðCOÞ þ n ions (n = 0-12) and silicon substrates was studied at a beam energy ranging from 2 keV to 10 keV at normal incidence. By adjusting Wien-filter voltage, the influence of CO ligands was investigated. Experimental results showed that sputtering yield of silicon bombarded with Ir 4 ðCOÞ þ n ions at 10 keV decreased with the number of CO ligands. In the case of 2 keV, deposition tended to be suppressed by removing CO ligands from the impinging cluster ions. The influence of CO ligands was explained by considering changes in surface properties caused by the irradiation of Ir 4 ðCOÞ þ n ions. It was also found that the bombardment with Ir 4 ðCOÞ þ 7 ions at 2.5 keV caused deposition on silicon target.

Research paper thumbnail of Production and Applications of Metal-cluster-complex Ion Beams

Journal of the Vacuum Society of Japan, 2009

A new ion source using massive molecules called metal cluster complexes has been developed. Metal... more A new ion source using massive molecules called metal cluster complexes has been developed. Metal cluster complexes are chemically-synthesized organometallic compounds, which have a wide range of chemical compositions with high molecular weight. The ion source is compact enough to be installed in commonly used secondary ion mass spectrometry (SIMS) systems. Using the ion source, sputtering characteristics of silicon bombarded with normally incident Ir4(CO)7+ ions were investigated. Experimental results showed that the sputtering yield at 10 keV was 36, which is higher than that with Ar+ ions by a factor of 24. In addition, SIMS analyses of boron-delta-doped silicon samples and organic films of poly(methyl methacrylate) (PMMA) were performed. Compared with conventional O2+ ion beams, Ir4(CO)7+ ion beams improved depth resolution by a factor of 2.5 at the same irradiation conditions; the highest depth resolution of 0.9 nm was obtained at 5 keV, 45° with oxygen flooding of 1.3×10-4 Pa. Furthermore, experimental results confirmed that Ir4(CO)7+ ion beams significantly enhanced secondary ion intensity in high-mass region.

Research paper thumbnail of Characteristics of a Metal-Cluster-Complex Ion Beam and Its Application to Secondary Ion Mass Spectrometry (SIMS)

Research paper thumbnail of Influence of thermal diffuse scattering and local stress on the precise measurement of Si1-xGex composition by convergent beam electron diffraction

e-Journal of Surface Science and Nanotechnology

Research paper thumbnail of Depth profiling for ultrashallow implants using backside secondary ion mass spectrometry

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2003

Research paper thumbnail of Laser-assisted atom probe tomography of 15N-enriched nitride thin films for analysis of nitrogen distribution in silicon-based structure

Applied Surface Science, 2015

Research paper thumbnail of Ultra-Thin (EOT ~ 0.31nm) and Low Leakage Dielectrics of La-Aluminate Deposited Directly on Si Substrate

ECS Transactions, 2006

ABSTRACT Ultra-thin (0.31 nm) LaAlO3 gate dielectrics directly deposited on Si substrate were rea... more ABSTRACT Ultra-thin (0.31 nm) LaAlO3 gate dielectrics directly deposited on Si substrate were realized. We found that LaAlO3 deposition at substrate temperature of 700{degree sign}C led to low defect density of the film at the as-deposited state. The electron mobility of LaAlO3 n-MISFET was improved by forming gas annealing, meaning that the defects at the direct interface could be passivated with hydrogen.

Research paper thumbnail of Cryo-Implantation Technology for Controlling Defects and impurity out diffusion

Research paper thumbnail of Contact resistance reduction of Pt-incorporated NiSi for continuous CMOS scaling ∼ Atomic level analysis of Pt/B/As distribution within silicide films &#x223C

2008 IEEE International Electron Devices Meeting, 2008

Platinum (Pt)-incorporation into nickel silicide films is the promising approach to reduce the co... more Platinum (Pt)-incorporation into nickel silicide films is the promising approach to reduce the contact resistance (RC) at silicide/Si interface. Physical properties of Ni1-xPtxSi films were investigated by using local electrode atom probe (LEAP); The distributions of Pt and dopants (such as As and B) were analyzed both at silicide/Si interface and at silicide grain boundary. The silicide grain-size miniaturization was

Research paper thumbnail of Investigation of the factors determining the SIMS depth resolution in silicon-isotope multiple layers

Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures, 2012

In order to identify their controlling factors, the depth resolution parameters for secondary ion... more In order to identify their controlling factors, the depth resolution parameters for secondary ion mass spectrometry, which include the decay length and the standard deviation of the Gaussian function (also referred to as the depth resolution function), for silicon atoms in a silicon matrix with silicon-isotope multiple layers were investigated under oxygen (O þ 2 ) and cesium (Cs þ ) ion bombardments with a wide ion energy range (from 200 eV to 10 keV) and with several incident angles. The use of silicon-isotope multiple layers in this investigation eliminated the chemical segregation effect caused by the sample composition. Measures were also taken to prevent ripple formation on the sputtered sample surface. The obtained depth resolution parameters were proportional to E 1/2 cos h, where E is the primary ion energy per atom and h is the incident angle relative to the surface normal. The relationships for decay length and standard deviation were different for the Cs þ ion, the O þ 2 ion with full oxidization, and the O þ 2 ion without full oxidization. The damage depth was measured by high-resolution Rutherford backscattering spectrometry and it was found that the relationships of the standard deviation versus damage depth depend only on the damage depth with a small dependence on the ion species (O þ 2 =Cs þ ). The degree of mixing near the sputtered surface of thin silicon-isotope multiple layers bombarded by O þ 2 =Cs þ ions was measured using laser-assisted atom probe analysis, and the relationship of the degree of mixing with the depth resolution parameters indicated that the decay length was degraded according to the degree of mixing. Atomic mixing/sputtering simulations revealed the factors determining the depth resolution parameters for secondary ion mass spectrometry. The standard deviation is found to be mainly degraded by the damage depth, which agrees with the results obtained by Rutherford backscattering spectrometry, whereas the decay length is mainly extended by the variance of the damage density profile, which is a parameter of the Gaussian function and governs the degree of mixing near the surface.

Research paper thumbnail of Characteristics of a cluster-ion beam of Os3(CO)n+ (n = 7 or 8) for low-damage sputtering

Surface and Interface Analysis, 2006

Research paper thumbnail of VAMAS round-robin study to evaluate a correction method for saturation effects in D-SIMS

Surface and Interface Analysis, 2014

ABSTRACT Recently, dynamic SIMS (D-SIMS) is being used to analyze ions simultaneously over a wide... more ABSTRACT Recently, dynamic SIMS (D-SIMS) is being used to analyze ions simultaneously over a wide range of concentrations, from matrix level to extremely low (ng g−1). However, D-SIMS detectors, which are mostly used in pulse counting systems, have problems with detector saturation. Thus, the ion intensities of SIMS must be corrected in their high-intensity region. It has been reported that the approximation intermediate extended dead-time model (a-IED model) can be used to correct saturated intensity in the higher region better than can the conventional model. In this study, we evaluated the usefulness of the a-IED model to correct partially saturated and saturated intensities for magnetic-sector-type D-SIMS and quadrupole-type D-SIMS for the effects of dead time. Nine organizations from five countries participated in this project. Analyzed specimens were an arsenic-implanted silicon wafer and a diffused BN onto Si wafer. The instruments used to analyze arsenic-implanted samples were five quadrupole-type SIMS and four magnetic-sector-type SIMS. The instruments used to analyze the BN-diffused samples were three quadrupole-type SIMS, four magnetic-sector-type SIMS, and one time-of-flight-type SIMS. We validated the usefulness of the a-IED model to correct saturated intensities for all SIMS in this round-robin test. The optimum extension parameter ρ tends to be affected by the ratio of the maximum reliable intensity to the maximum intensity. Copyright © 2014 John Wiley & Sons, Ltd.

Research paper thumbnail of Secondary ion yields depending on the primary oxygen ion energy in cameca IMS-4f instrument

Surface and Interface Analysis, 1994

ABSTRACT

Research paper thumbnail of An effect of measurement conditions on the depth resolution for low-energy dual-beam depth profiling using TOF-SIMS

Surface and Interface Analysis, 2013

ABSTRACT An effect of measurement conditions on the depth resolution was investigated for dual-be... more ABSTRACT An effect of measurement conditions on the depth resolution was investigated for dual-beam time of flight-secondary ion mass spectrometry depth profiling of delta-doped-boron multi-layers in silicon with a low-energy sputter ion (200 eV – 2 keV O2+) and with a high-energy primary ion (30 keV Bi+). The depth resolution was evaluated by the intensity ratio of the first peak and the subsequent valley in B+ depth profile for each measurement condition. In the case of sputtering with the low energy of 250 eV, the depth resolution was found to be affected by the damage with the high-energy primary ion (Bi+) and was found to be correlated to the ratio of current density of sputter ion to primary ion. From the depth profiles of implanted Bi+ primary ion remaining at the analysis area, it was proposed that the influence of high-energy primary ion to the depth resolution can be explained with a damage accumulation model. Copyright © 2013 John Wiley & Sons, Ltd.

Research paper thumbnail of Secondary ion mass spectrometry round-robin study of relative sensitivity factors in gallium arsenide

Surface and Interface Analysis, 1998

ABSTRACT

Research paper thumbnail of High-sensitivity x-ray absorption fine structure investigation of arsenic shallow implant in silicon

Spectrochimica Acta Part B: Atomic Spectroscopy, 2009

High-sensitivity fluorescence-yield x-ray absorption fine structure spectroscopy (XAFS) has been ... more High-sensitivity fluorescence-yield x-ray absorption fine structure spectroscopy (XAFS) has been investigated to characterize the local structure around arsenic shallow implant in silicon. Fluorescence-yield XAFS experiments were performed using a high-brilliance synchrotron radiation beam from an in-vacuum-type undulator in a third-generation light source. In addition to investigating the efficiency of high-brilliance undulator x-rays during the fluorescence-yield XAFS measurements, we compared the analytical performance of both the wavelength dispersive spectrometer (WDS) and the energy dispersive spectrometer (EDS) based on the silicon drift detector (SDD). It was confirmed that the WDS reduces the influence of scattering background due to the high spectral resolution. Another advantage of the WDS is high counting rate measurements. It was found that fluorescence-yield XAFS using undulator x-rays combined with the WDS permits superior sensitivity measurements.

Research paper thumbnail of SIMS depth profile study using metal cluster complex ion bombardment

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007

SIMS depth profiles using a metal cluster complex ion of Ir 4 ðCOÞ þ 7 were studied. An unusual i... more SIMS depth profiles using a metal cluster complex ion of Ir 4 ðCOÞ þ 7 were studied. An unusual increase of the sputtering yield under the condition of small incident angle may be attributed to the suppression of taking oxygen from flooding O 2 by the formation of a carbon cover-layer derived from Ir 4 ðCOÞ þ 7 ion. Even though the roughness of the sputtered surface is small, the depth resolution was not improved by decreasing the cluster ion energy to less than 5 keV, because the carbon cover-layer prevents the formation of surface oxide that buffers atomic mixing. To overcome this issue, it will be necessary to eliminate carbon from the cluster ion.