2021
A report about limiting current-type MEMS oxygen sensor. This
report includes the fabrication method and sensing property of
oxygen sensor.
Sintered silver (s-Ag) has attracted so many researchers due to
its high heat conductivity. Applying power module products for
die attach part, the degradation has been evaluated by thermal
shocked test (TST). Therefore, understanding of the degradation
mechanism during TST is an eseential role for designing power
modules. The objective of this study is to compare degradation
mechanism between TST and four-point bending test to understand
s-Ag die attach failure in power module products under
operation.
The electronic states of twisted bilayer graphene (TBG) vary
with its twist angle. In this study, we obtained 5 × 5 mm^2 TBG
samples with various twist angle, using epi-graphene on SiC.
Furthermore, angle-resolved photoemission spectroscopy revealed
their energy band structures.
The toroidal coil shape was automatically optimized using neural
networks and genetic algorithm.
We have developed a technology to integrate terahertz devices in
rectangular waveguides with low loss by using dielectric
transmission lines.
A module in which a resonant tunneling
diode is packaged using a photonic crystal waveguide was
fabricated, and wireless communication was demonstrated.
We proposed a backside-coupling structure for efficient and
broadband coupling of terahertz resonant tunneling diodes and
phoonics-crystal waveguides, and demonstrated its operation in
the 300-GHz band.
Expanding SiC power device market requires lowering wafer prices
for the majority of device costs. In this talk, the author
reports the application of remote epitaxy technology to
alternative substrate with epi-membrane. SiC remote epitaxy
needs high growth temperature with hot-wall chemical vapor
deposition around 1873 K, which is a harsh environment for
graphene survival. By replacing the carrier gas from hydrogen to
argon, graphene etching was suppressed and peeling was
successful. The author believes this approach represents a
significant step toward the fabrication of high quality and low
cost substrate with epi.
The Compact model of GaN Ridge HEMTs, especially the drain
current increase due to gate injection, has been improved from
the one presented at APEC2020, and a scalable model equation has
been derived by considering the physical generation mechanism.
In addition, we analized the effect of the current gain H21 on
the frequency response when the device is operated in AC. With
this model, the H21 characteristics in the current-increasing
region due to gate injection agreed with the actual measurement
with high accuracy.
We propose a results of a simple motor inverter simulation with
WLTC droving mode using PLECS. PLECS is the simulation platform
of power electric systems.
In coated Cu substrate was used as a low melting temperature
bonding. We optimized the joint condition such as a temperature,
pressure and process.
The third-generation wireless in-wheel motor (W-IWM3) which has
the capability of the Dynamic Wireless Power Transfer (D-WPT) on
its wheel side has been developed for the Electric Vehicles.
Developing concepts of W-IWM3 targeting “all components in
wheel” is realized. One of the factors for “all components in
wheel” is the small silicon-carbide (SiC) power device authors
have developed. This paper showed the test result that the more
than 18kW output with 95.2% DC to DC efficiency was achieved.
We propose a SiC MOSFET model for circuit simulation. We
validated the accuracy of the proposed model by measured
switching waveforms of an inductive load switching evaluation
circuit. Simulation speed of the model has been validated by a
three-phase inverter simulation. Excellent results have been
observed for both accuracy and speed.
Pb-2Sn-2.5Ag alloy solder is one of the most popular materials
for die attach in electronic devices, however its mechanical
properties have not been reported. In this study, we measured
the visco-elasto-plastic properties of Pb-2Sn-2.5Ag solder using
Instrumented Indentation microscopy with an optically
transparent indenter.
Since high lead solder has been used in industry for many years,
few basic studies have been reported that discuss the
microstructure and mechanical properties. In this study, the
relationship between the microstructure and mechanical
properties of high lead solder joints was investigated.
2020
Developping a method to track GaN transistor degradation over
time with recurrent neural networks. From measurements easily
obtained during the normal operation of the transistor we can
detect if the behavior is standard or if there is an anomaly.
This method should enable live monitoring of device health.
We employed a single resonant tunneling diode as both a
transmitter and a receiver simultaneously, and demonstrated its
impact in terahertz imaging applications.It leads to simplify
terahertz imaging systems.
Influence of device parameter variation on current sharing
between SiC MOSFETs connected in parallel has been studied. From
the simulation results, we reveal the device parameters which
mainly affetct the static and dynamic current sharing behavior
of the devices. We also evaluate the effect of the current
sharing mismatch on energy loss for each device.
The presentation reveals the pore size and shape dependences
on sintered silver mechanical durabilities.
From
stress-strain results, uniform crystal structure
make sphere and small pore shape. In terms of
thermal cycle reliability using sintered silver materials,
uniform structure with small and sphere pore state is essential.
A method to diagnose whether the accelerometer itself is in a
state of mechanical deterioration by statistically examining the
output data from the accelerometer while the machine health
monitoring application system is in continuous operation.
The Id-Vd charactaristic in high-Id and high-Vd range of
SiC-MOSFET shows incremental trend instead of saturated Id
behavior. By TCAD simulation, the self-heating at measurement
reproduce well this incremental trend.
In the evaluation of the impurity level depth in Zn-doped GaN,
it was found that Zn behaves as an acceptor impurity in GaN by
forming the state at 0.3 eV from the top of the valence band.
Normaly-off operation was confirmed in an AlGaN/GaN HFET with a
0.1 μm mesa shape using Zn-doped GaN as the gate layer.
To maximise the switching capability of SiC-MOSFET, we introduce
a current and voltage hybrid source gate driver and design
method.
The adoption of small Qoss and small Qg GaN transistors was
found to be a useful option to solve both the miniaturization
and high power conversion efficiency of switching power
supplies. Isolated 48 V-12 V LLC converter with a switching
frequency of 2 MHz and 100 W class was fabricated, and the
maximum power conversion efficiency reached 95.3%.
The basic characteristics of the latest generation of ROHM's
SiC-MOSFETs are presented and compared with the current
generation of devices in production. On the other hand, it is
often assumed that better power device characteristics improve
power-circuit performace, but it is not that simple. For better
system-level performance, our researches of power applications
and the related simulations are also presented.
This research investigates how the mechanical properties of
sintered silver (s-Ag) as a die attach material influence its
heat-cycle reliability. s-Ag mechanical fatigue life was 500
times under elastic stress. To investigate the correlation
between fatigue mechanical test and thermal shocked test (TST),
we performed TST with different temperature patterns. From TST
results, higher TST gives faster degradation of s-Ag.
Twisted bilyaer graphene can be mocified the energy band
structure by changing the rotation angle. Especially, the
1.1degree called as a magic angle can be shown the
superconductivity. However, the next challenge is to obtain big
scale (millimeter-scale) TBG samples. This research was shown to
obtain it with using transfer graphene after annealing.
The method to control graphene angle on C face in SiC(000-1) is
not performed, so this research is challenging to control it.
We have devloped the world's first small general-purpose
PLCC package and a high-gain antenna integrated package for
terahertz devices. There are promising as a high-frequency
package form that are functional and can be mass produced.
This paper presents a semi-theoretical method for predicting the
turn-off surge voltage (Vsurge) in double-pulse test (DPT) using
a power module (PM) with SiC MOSFETs and an embedded DC-link
decoupling capacitor. In this scheme, multiple Kirchhoff’s
laws-based equations are simultaneously solved, and drain-source
voltage and drain current are mathematically expressed. This
calculation process is semi-theoretical, and sufficiently
predicts the Vsurge observed in DPT performed under various
conditions.
2019
The modeling method developed in SiC DMOS was applied to the SiC
UMOS and its versatility was verified. The model was also
evaluated by comparing the switching waveforms fo a power module
with SiC UMOS chip. As a result, the SiC UMOS model reproduced
the measurement data with high accuracy as well as the SiC DMOS.
The fatigue mechanical property of sintered silver plays a
critical role to estimate the reliability of systems. The
tensile fatigue test is performed for the sintered silver with
p=5% and the bulk silver. The fatigue lifetime of the silver
films is shorter than that of the bulk silver one.
Demonstrate the dynamic on-state resistance of GaN-HEMT and
estimate inpact of loss of devices.
This study report that high speed switching gate drive circuit
for SiC MOSFETs. The provided gate drive circuit adapted
subsidery capacitor in order to add gate voltage, enables
increase gate current. This allows fast charge and discharge and
reduced switching losses. This study confirmed that the provided
gate drive circuit reduce switching loss compared to
conventional one.
A novel measurement method to extract high voltage and high
current I-V characteristics (HVHC I-V)of SiC MOSFET is proposed
in this paper. The method could extract the HVHC I-V with
extremely reduced self heating of the device. By using the
method, we can measure higher voltage and current I-V
characteristics than those extracted by the conventional method.
It is possible for us to measure the HVHC I-V of the next
generation SiC MOSFET, whose rated volatge and current is more
than those of the conventional device.
The internal gate resistance of SiC MOSFET effects its switching
behavior larger than Si devices because it can switch at high
speed with low external gate resistance. However, the convention
mesurement method of internal gate resistance is not accurate.
Then, we devised the new measurement method of it at switching
operation by the switching waveforms.
銀焼成は、空孔率がその引張り機械特性に影響することがわかっている。ところが、銀焼成の疲労機械特性について未だ不明である。今回我々は多孔質銀焼成の薄膜試験片と銀膜の疲労試験を実施した。銀焼成膜は、高加圧条件(60MPa)で成膜し、空孔率は5％であった。疲労試験結果から、焼成膜の引張疲労強度は銀膜と比較して低下しやすいことが分かった。
ロームの高度な分析・解析技術により、PZT薄膜のドライエッチング中に起こる形態変化がPZTの結晶方位が変動する現象に起因することを突き止めた。
SiC,GaNのパワーデバイスを開発するだけでなく、それらを使いこなすための技術も伴わないと社会貢献することはできない。本講演では、アプリケーションの実例、それを支える設計技術、ノイズの予測について紹介する
The precise modeling of SiC MOSFETs are difficult by means of
conventional modeling method of Si devices because of the device
characteristics. Then, we invented the new modeling method for
SiC MOSFETs which can reproduce its switching behavior
precisely.
A 3-phase15kW using SiC MOSFETs and trans-linked topology
achieved maximum efficiency of 99.2%, and verified the benefit
of combining SiC MOSFET with trans-linked technology.
IoT社会では、モノやヒトの状態や変化をセンシングして得られるデータを収集し、生産性や環境の改善、安全や安心の向上、セキュリティの強化等のアプリケーションで活用している。本講演では、デバイスにフォーカスし、IoTアプリケーション事例を述べ、将来技術としてのエネルギーハーベスティングについても述べた。
電流形と電圧形を組み合わせたSiC-MOSFET用ハイブリッド形ゲート駆動回路の実機実験により、ターンオン損失が50%、ターンオフ損失が35%低減できることを実証した。
SiC-MOSFETを高速に駆動できるゲート駆動回路についての報告。本ゲート駆動回路は補助キャパシタを用いており、この補助キャパシタを介してゲートに通常よりも高い電圧を印加することができ、ゲート電流を増加させることができる。これにより高速にゲートを充放電し、スイッチング損失を低減できる。実測でもこの効果を確認し、本回路の優位性を実証した。
2018
This paper investigates the porosity-dependent tensile
mechanical properties of porous 8-10 μm thick silver films. The
silver films are fabricated by pressure press, the variety of
which changes the porosity (p) ranging 5% to 25%. p is
determined by use of scanning electron microscopy cross-section
images of the films. Stress-strain (S-S) curves are obtained by
tensile tests performed for the porous and bulk silver
films.Breaking strain and Ultimate tensile strengh decrease
almost linearly with increase of p.
SiC,GaNのパワーデバイスを開発するだけでなく、それらを使いこなすための技術も伴わないと社会貢献することはできない。本講演では、アプリケーションの実例、それを支える設計技術について紹介する
Workshop: Introduced RTD devices for THz communication and
sensing. With comparison with other terahertz device, RTDs are
compact and power-efficient.
The mechanical properties of die-attach materials are a decisive
factor in determing the reliability of the system. Sintered
porous silver is attracting much attention as a next-generation
die-attach material,however still do not clalify the mechanical
properties. Authors prepared thin sintered silver and bulk
silver films.Sintered silver films were fabricated under various
pressure. From tensile tests, Sintered porous silver films
exhibit brittle characteristic in comparison with silver films
and show high strength under high process pressure.
A number of IoT applications are rapidly growing. Among others,
smart factory, smart infrastructure and digital medicine/health
are major IoT markets. ROHM also succeeded in demonstration of
healthcare monitoring utilizing non-volatile PZT devices. The
essentials for IoT society and ROHM’s device applications of PZT
thin film were described.
A Scalable drain current model and a small-signal AC model have
been developed for AlGaN/GaN MIS HEMTs with embedded source
field plate. The model was found to reproduce the device
characteristics well by comparing the Id-Vds, Id-Vgs, S11and H21
characteristics of the device.
A trans-linked 5kW interleaved inverter using SiC MOSFETs
drastically reduced both tansistor loss and reactor losses,
resulting in high efficiency over 99% and fanless operation.
The accurate electro-thermal simulation is presented by using a
new SiC die model to predict the power loss and temperature of
SiC MOSFET dies in a power module. The new model incorporates a
temperature dependent I-V model and body diode model which is
dependent on the gate-voltage. The simulation using the model
yields an accurate power loss and temperature estimate of the
SiC module in a buck converter.
S-parameter based simulation model for power module (PM) except
for the semiconductor chips was created with electromagnetic
simulation. This PM model was combined with the chip model in
order to build the model of the whole structure. As a result of
verifying the model by the double pulse test, the simulation
waveforms which reproduce the measurement results well were
obtained.
ROHM has developed PZT thin film devices, such as non-volatile
ferroelectric memory, highly-sensitive sensors, highly-accurate
actuators, high-speed space light modulators and
ultra-low-power-consumption non-volatile flip-flop devices so
far. ROHM also succeeded in demonstration of healthcare
monitoring utilizing non-volatile PZT devices (memory and
logic). In this presentation, ROHM’s device applications of PZT
thin film were described.
We have proposed a new hybrid structure of the PZT film which we
made by sol-gel method of construction on the PbTiO3 seed layer
made by rf magnetron sputtering. These hybrid PZT films showed
high (100)/(001) orientation and had high breakdown voltage.
電流形と電圧形を組み合わせたSiC-MOSFET用ハイブリッド形ゲート駆動回路を提案し、シミュレーションにてゲート電圧の安定性とスイッチング損失の低減ができることを確認した。
The high speed switching of SiC MOSFET is affected by the
parasitic elements of circuit board. Therefore, we analyzed the
impact of stray capacitance in circuit board on the switching
behavior and tried circuit simulation of the effect by use of
precise model and electromagnetic simulation results of circuit
board.
2017
Present the recent advance of RTD-based terahertz devices.
Based on a well-defined equivalent circuit model,
circuits like mixer, detector, and oscillators have
been integrated.
IoT社会におけるPZTデバイスの位置付けについて述べ、ロームのPZTデバイス技術（メモリからセンサ/アクチュエータ）を概観した。最近の取組み事例として、「不揮発ロジックデバイス」と「ピエゾMEMSデバイス」を紹介した。
This study report that a three-phase, 5-kW LLC series resonant
dc/dc converter utilizing SiC MOSFETs. The high-break down
voltage of SiC MOSFETs, enables increasing the input voltage up
to 800 V. Around 160kHz switchig frequency successfully reduces
the volume of isolation transformers. Current-balancing
transformers among each phases effectively suppress a peak
current from arising in the circuit and contributed that
miniaturizes the input and output capacitances. The proposed
power supply weighs 1.55 kg with dimensions including a width of
18 cm, a length of 12 cm, and a height of 12.5cm. The conversion
efficiency of the converter reaches 98.1% at 5-kW operation.
2016
本講演では、IoTにおけるセンサの重要性を示し、MEMSセンサ、及びIoT/ワイヤレスセンサネットワークについて述べ、更にはアプリケーション開拓に向けた検証としてのセンサソリューションについても述べた。
Progress In Electromagnetics Research Symposium 2016 China
Until now, the transientcharacteristics of circuit simulations
using the SiC device model have not been consistent. Since EMC
must be considered when using SiC Devices, it is important to
reproduce their transient characteristics. Therefore, we have
developed a novel SiC devie model by measureing the Id-Vds
characteristics with the high-voltage and high-current region
and the on-state capacitance of the SiC MOSFET to reproduce the
transient characteristics. As a result the novel SiC device
model successfully reproduce the switching taransient waveform
with high accuracy.
IoT世界においては、トリリオンセンサに代表されるように大量のセンサがネットワークでつながり、暮らしの省エネから快適性・安全性を高めていく。本講演では、各種センサとセンサネットワークへの取り組み、ヘルスケアに必要な常時モニタリングについて紹介した。
2015
The self-sustained oscillations are sometimes obserbed when SiC
MOSFETs switch at high speed in the half bridge configuration.
The oscillation is regard as nonlinear self-excited oscillation
as a result of its device characteristics. We tried to analyze
it from the aspects of device characteristics of MOSFET and
trajectory of the oscillation in the I-V plane.
