廣瀬 和之

We analyzed light element impurities in ultrathin top Si layers of silicon-on-insulator (SOI) wafers by luminescence activation using electron irradiation. Photoluminescence (PL) analysis under ultraviolet (UV) light excitation was performed on various commercial SOI wafers after the irradiation. We detected the C-line related to a complex of interstitial carbon and oxygen impurities and the G-line related to a complex of interstitial and substitutional carbon impurities in the top Si layer with a thickness down to 62 nm after electron irradiation. We showed that there were differences in the impurity concentration depending on the wafer fabrication methods and also that there were variations in these concentrations in the respective wafers. Xenon ion implantation was used to activate top Si layers selectively so that we could confirm that the PL signal under the UV light excitation comes not from substrates but from top Si layers. The present method is a very promising tool to evaluate the light element impurities in top Si layers. (C) 2009 The Japan Society of Applied Physics

Single event transient (SET) pulse-widths were measured as a function of linear energy transfer (LET) by using pulse capture circuits and simulated with mixed-mode 3-D device simulations. We found that the carrier recombination process dominates the LET dependence of the pulse-widths.

Single event transient (SET) pulse-widths were measured as a function of linear energy transfer (LET) by using pulse capture circuits and simulated with mixed-mode 3-D device simulations. We found that the carrier recombination process dominates the LET dependence of the pulse-widths.

Radiation-induced pulse noises called single-event transients, SETs, are becoming a serious soft-error source for logic VLSIs. Analytical models explicitly expressing the relationship between the pulse width and radiation/device/circuit parameters are desired as guidelines to develop optimized countermeasures. A simple mathematical expression is devised for characterizing SET pulse widths in SOI CMOS technologies. It is based on the physical mechanisms of the SETs and on the idea of Moll's storage time. Device simulations demonstrate that the expression explains pulse-width trends properly for large radiation-induced noise charges.

Radiation-induced pulse noises called single-event transients, SETs, are becoming a serious soft-error source for logic VLSIs. Analytical models explicitly expressing the relationship between the pulse width and radiation/device/circuit parameters are desired as guidelines to develop optimized countermeasures. A simple mathematical expression is devised for characterizing SET pulse widths in SOI CMOS technologies. It is based on the physical mechanisms of the SETs and on the idea of Moll's storage time. Device simulations demonstrate that the expression explains pulse-width trends properly for large radiation-induced noise charges.

Waveforms of digital single-event transients, radiation-induced voltage transients in logic gates, can be observed by connecting two transistors to a target logic gate. Additional transistors monitor voltage transients through their drain currents, which can be measured using the conventional 50-Omega transmission-line technique widely used for measuring transient currents in single elementary transistors. Experimental results obtained in pulsed-laser irradiation tests demonstrate the validity of the observation technique and clearly reveal the pulse evolution as a function of the laser pulse energy.

Waveforms of digital single-event transients, radiation-induced voltage transients in logic gates, can be observed by connecting two transistors to a target logic gate. Additional transistors monitor voltage transients through their drain currents, which can be measured using the conventional 50-Omega transmission-line technique widely used for measuring transient currents in single elementary transistors. Experimental results obtained in pulsed-laser irradiation tests demonstrate the validity of the observation technique and clearly reveal the pulse evolution as a function of the laser pulse energy.

We calculate the difference between the valence charges of the ground state and the Slater transition state for several types of Si compounds and Al compounds. We assume the dipole moment induced by core-hole generation at the Slater transition state to be the product of the valence charge difference and the bond length of the compounds. We find that the calculated dipole moment has a strong linear correlation well with (epsilon-1)/(epsilon+2), which is deduced from experimental values of the optical dielectric constant epsilon.

放射線によって論理LSI内に誘起されるスパイクノイズがソフトエラー源として顕在化してきている.論理LSIはチップ内部に多数のフリップフロップ(FF)やラッチ回路を保持しており,その記憶データが反転するとソフトエラーが起きる.論理LSIでは,放射線がFFやラッチ回路に当たってソフトエラーが起きるだけでなく,組み合わせ論理回路に当たって発生するスパイクノイズによってもソフトエラーが起きる.発生するスパイクノイズの長さが長くなるとソフトエラーの発生率が増加してしまう.そのため,スパイクノイズの放射線入射空LET依存性を測定した.また,放射線がFFやラッチ回路に当たって発生するソフトエラーだけでなく,組み合わせ論理回路に当たって発生するソフトエラー両方の影響をそれぞれ評価する必要がある.さらに各FFでどれだけデータが反転,すなわちソフトエラーが起きたか知る必要がある.これらの要求を満たす新しいLSIテスト技術を開発し,その妥当性を実証した.

'HAYABUSA' is a Japanese inter-planetary spacecraft built for the exploration of an asteroid named 'ITOKAWA.' The spacecraft is powered by a 13.2 Ah lithium-ion secondary battery. To realize maximum performance of the battery for long flight operation, the state-of-charge (SOC) of the battery was maintained at ca. 65% during storage, in case it is required for a loss of attitude control. The capacity of the battery was measured during flight operations. Along with the operation in orbit, a ground-test battery was discharged, and both results showed a good agreement. This result confirmed that the performance of the lithium-ion secondary battery stored under micro-gravity conditions is predictable using a ground-test battery. (C) 2008 Published by Elsevier B.V.

'HAYABUSA' is a Japanese inter-planetary spacecraft built for the exploration of an asteroid named 'ITOKAWA.' The spacecraft is powered by a 13.2 Ah lithium-ion secondary battery. To realize maximum performance of the battery for long flight operation, the state-of-charge (SOC) of the battery was maintained at ca. 65% during storage, in case it is required for a loss of attitude control. The capacity of the battery was measured during flight operations. Along with the operation in orbit, a ground-test battery was discharged, and both results showed a good agreement. This result confirmed that the performance of the lithium-ion secondary battery stored under micro-gravity conditions is predictable using a ground-test battery. (C) 2008 Published by Elsevier B.V.

We investigated proton irradiation effects on Cu(In,Ga)Se-2 (CIGS) solar cells with a structure of ZnO/CdS/CIGS using photoluminescence (PL) spectroscopy. After proton irradiation, near band-edge emission from the CIGS layer was considerably reduced, while deep-level emission emerged at 0.8 eV. Subsequent annealing restored the intensity of the near band-edge emission slightly, and reduced the 0.8 eV band substantially. An anomalous spectral variation caused by the annealing suggests that the 0.8 eV band does not originate from a single irradiation-induced defect. After the irradiation, the 1.35 eV emission from the US layer was moderately reduced, and the band-edge emission from the ZnO layer had disappeared. These bands recovered to the initial state after the annealing. Qualitative correlation was observed between the PL properties and the electrical properties of the cell.

We calculate the difference between the valence charges of the ground state and the Slater transition state for several types of Si compounds and Al compounds. We assume the dipole moment induced by core-hole generation at the Slater transition state to be the product of the valence charge difference and the bond length of the compounds. We find that the calculated dipole moment has a strong linear correlation well with (ε-1) / (ε+2), which is deduced from experimental values of the optical dielectric constant ε. © 2008 American Institute of Physics.

We find a new relationship between the optical dielectric constant of Al dielectric films and their chemical shifts measured by X- ray photoelectron spectroscopy (XPS). We measure the difference between core-level binding energy shift for Al 1s and core-level binding energy shift for Al 2p, Delta E-1s - Delta E-2p, for AlN using high- resolution high- energy synchrotron radiation. We find that Delta E-1s - Delta E-2p correlates well with the optical dielectric constants of Al, AlN, and Al2O3. This is consistent with the case of our previously reported Si compounds. First-principles calculations are performed to determine the mechanism behind the observed correlation.

We find a new relationship between the optical dielectric constant of Al dielectric films and their chemical shifts measured by X- ray photoelectron spectroscopy (XPS). We measure the difference between core-level binding energy shift for Al 1s and core-level binding energy shift for Al 2p, Delta E-1s - Delta E-2p, for AlN using high- resolution high- energy synchrotron radiation. We find that Delta E-1s - Delta E-2p correlates well with the optical dielectric constants of Al, AlN, and Al2O3. This is consistent with the case of our previously reported Si compounds. First-principles calculations are performed to determine the mechanism behind the observed correlation.

A table-based technique for estimating single-event transient pulses is evaluated in the most crucial case for bulk MOSFET technologies where an ion penetrates the drain region. A device model of a bulk MOSFET is built in a 2-D numerical device simulation framework, and heavy-ion-induced transient currents flowing through its drain terminal are calculated. From the currents, single-event transient voltage pulses in an inverter are estimated with the table-based estimation technique. The results are compared with ones simulated in the mixed mode with the same device model and circuit configuration. The estimated pulses are comparable to the results in the mixed-mode device simulations. Moreover, the estimation accuracy can be improved by using a drain-capacitance compensation technique. An extrapolation technique based on the drain-voltage dependency of heavy-ion-induced transient currents is also presented to reduce the experimental costs for modeling.

The effects of heavy ion energy and nuclear interactions on the single-event upset (SEU) and single-event latchup (SEL) response of commercial and radiation-hardened CMOS ICs are explored. Above the threshold LET for direct ionization-induced upsets, little difference is observed in single-event upset and latchup cross sections measured using low versus high energy heavy ions. However, significant differences between low- and high-energy heavy ion test results are observed below the threshold LET for single-node direct ionization-induced upsets. The data suggest that secondary particles produced by nuclear interactions play a role in determining the SEU and SEL hardness of integrated circuits, especially at low LET. The role of nuclear interactions and implications for radiation hardness assurance and rate prediction are discussed.

The Japanese spacecraft, HAYABUSA, was launched on May 9, 2003 and spent more than 2.5 years approaching the asteroid ITOKAWA. This spacecraft used 13.2 Ah lithium-ion secondary cells. After HAYABUSA touched down on ITOKAWA in December 2005, it could not communicate for seven weeks due to a malfunction of the attitude control. During this period, four of 11 lithium-ion secondary cells were over-discharged, and solar power was unavailable due to the spacecraft's tumbling motion. However, the battery power was still indispensable for sealing the container with the asteroid sample. The seven remaining healthy cells were slowly recharged using minimum current. During this time, ground simulation tests using similarly-built and intentionally short-circuited cells were carried out to evaluate the battery's operational safety. After its safety was confirmed, the lithium-ion secondary battery was used to transfer, latch, and successfully seal the sample container into the reentry capsule. The necessary power for these actions was supplied by the battery.

A table-based technique for estimating single-event transient pulses is evaluated in the most crucial case for bulk MOSFET technologies where an ion penetrates the drain region. A device model of a bulk MOSFET is built in a 2-D numerical device simulation framework, and heavy-ion-induced transient currents flowing through its drain terminal are calculated. From the currents, single-event transient voltage pulses in an inverter are estimated with the table-based estimation technique. The results are compared with ones simulated in the mixed mode with the same device model and circuit configuration. The estimated pulses are comparable to the results in the mixed-mode device simulations. Moreover, the estimation accuracy can be improved by using a drain-capacitance compensation technique. An extrapolation technique based on the drain-voltage dependency of heavy-ion-induced transient currents is also presented to reduce the experimental costs for modeling.

The effects of heavy ion energy and nuclear interactions on the single-event upset (SEU) and single-event latchup (SEL) response of commercial and radiation-hardened CMOS ICs are explored. Above the threshold LET for direct ionization-induced upsets, little difference is observed in single-event upset and latchup cross sections measured using low versus high energy heavy ions. However, significant differences between low- and high-energy heavy ion test results are observed below the threshold LET for single-node direct ionization-induced upsets. The data suggest that secondary particles produced by nuclear interactions play a role in determining the SEU and SEL hardness of integrated circuits, especially at low LET. The role of nuclear interactions and implications for radiation hardness assurance and rate prediction are discussed.

The Japanese spacecraft, HAYABUSA, was launched on May 9, 2003 and spent more than 2.5 years approaching the asteroid ITOKAWA. This spacecraft used 13.2 Ah lithium-ion secondary cells. After HAYABUSA touched down on ITOKAWA in December 2005, it could not communicate for seven weeks due to a malfunction of the attitude control. During this period, four of 11 lithium-ion secondary cells were over-discharged, and solar power was unavailable due to the spacecraft's tumbling motion. However, the battery power was still indispensable for sealing the container with the asteroid sample. The seven remaining healthy cells were slowly recharged using minimum current. During this time, ground simulation tests using similarly-built and intentionally short-circuited cells were carried out to evaluate the battery's operational safety. After its safety was confirmed, the lithium-ion secondary battery was used to transfer, latch, and successfully seal the sample container into the reentry capsule. The necessary power for these actions was supplied by the battery.

宇宙航空研究開発機構では、2010年の打ち上げを目指して金星探査機PLANET-Cの開発を進めている。本稿では、電源系サブシステムの概要について述べた後、特に太陽電池パネルおよびバッテリの評価試験について報告する。太陽電池パネルは、およそ-170〜+170℃の厳しい温度サイクルに耐えて期待される性能を発揮することが確認された。また、バッテリについては実際の運用パターンを模擬した評価試験が進行中で、可能な限り劣化を抑えた運用方法を検討している。

In order to confirm benefits of a deep sub-micron FD-SOI and to identify possible issues concerning front-end circuits with the FD-SOI, we have submitted a small design to Oki Electric Industry Co., Ltd. via the multi-chip project service of VDEC, the University of Tokyo. The initial test results and future plans for development are presented. (c) 2007 Elsevier B.V. All rights reserved.

In order to confirm benefits of a deep sub-micron FD-SOI and to identify possible issues concerning front-end circuits with the FD-SOI, we have submitted a small design to Oki Electric Industry Co., Ltd. via the multi-chip project service of VDEC, the University of Tokyo. The initial test results and future plans for development are presented. (c) 2007 Elsevier B.V. All rights reserved.

Described is an estimation technique,of single event transient voltage pulses in VLSI circuits from heavy-ion-induced transient currents measured in a single MOSFET. Waveforms of the transient voltage pulses are fully estimated by using transient current data obtained in various drain voltage conditions. Modeling of the irradiated device behavior for use in device/circuit simulations is not required. The concept is validated using a 2-D mixed-mode device simulation.

The impact of heavy ion energy on SEU and SEL in commercial and radiation-hardened CMOS SRAMs is explored. Provided the ion range is large enough for the ions to reach the sensitive device region, standard low-energy heavy ion testing is conservative with respect to high-energy heavy ions, at least for LETs above the threshold for direct ionization-induced upsets. However, below the threshold LET for direct ionization-induced effects we find some differences between low- and high-energy tests. These differences are attributed to the effects of nuclear reaction-induced secondary particles. Implications for hardness assurance testing and error rate calculations are discussed.

Described is an estimation technique,of single event transient voltage pulses in VLSI circuits from heavy-ion-induced transient currents measured in a single MOSFET. Waveforms of the transient voltage pulses are fully estimated by using transient current data obtained in various drain voltage conditions. Modeling of the irradiated device behavior for use in device/circuit simulations is not required. The concept is validated using a 2-D mixed-mode device simulation.

The impact of heavy ion energy on SEU and SEL in commercial and radiation-hardened CMOS SRAMs is explored. Provided the ion range is large enough for the ions to reach the sensitive device region, standard low-energy heavy ion testing is conservative with respect to high-energy heavy ions, at least for LETs above the threshold for direct ionization-induced upsets. However, below the threshold LET for direct ionization-induced effects we find some differences between low- and high-energy tests. These differences are attributed to the effects of nuclear reaction-induced secondary particles. Implications for hardness assurance testing and error rate calculations are discussed.

'HAYABUSA' is a Japanese interplanetary spacecraft for the exploration of an asteroid named 'ITOKAWA.' The spacecraft is powered by a 13.2 Ah lithium-ion secondary battery. To realize maximum performance of the battery for long flight operation, the state-of-charge (SOC) of the battery was maintained at ca. 65% during storage in case it is required for contingency operations. To maintain this SOC condition, the battery is charged once a week. We further charge the battery up to 4.1 V/cell using bypass circuits to balance the cells every four months. The capacity of the battery was measured during the flight operation, which revealed the appropriate capacity for the expected mission.

'HAYABUSA' is a Japanese interplanetary spacecraft for the exploration of an asteroid named 'ITOKAWA.' The spacecraft is powered by a 13.2 Ah lithium-ion secondary battery. To realize maximum performance of the battery for long flight operation, the state-of-charge (SOC) of the battery was maintained at ca. 65% during storage in case it is required for contingency operations. To maintain this SOC condition, the battery is charged once a week. We further charge the battery up to 4.1 V/cell using bypass circuits to balance the cells every four months. The capacity of the battery was measured during the flight operation, which revealed the appropriate capacity for the expected mission.