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Abstract : Vol.39No.4(2004.12)
Special Issue：Recent
R&D Activities of Power Devices for Hybrid Electric
Vehicles
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Review
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Recent
R&D Activities of Power Devices for Hybrid Electric
Vehicles |
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Automobiles have an influence
on the global environment that cannot be disregarded,
not only through air pollution in cities but also through
large carbon dioxide emission that leads to global warming.
A hybrid electric vehicle combining a gasoline engine
and an electric motor has proved to be an effective
means to solve these problems. Electrical energy flow
of the vehicle is controlled with inverters built into
the car. These inverters consist of power modules that
in turn contain many power devices. Therefore, power
devices are one of the key components for the hybrid
electric vehicle. In this paper, we make a survey of
the role of power devices used in the hybrid electric
vehicle and the technological trends they indicate.
In addition, we present our recent R&D activities
concerning power devices.
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| P.7 |
Proposal
of a New High Power Insulated Gate Bipolar Transistor |
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Sachiko Kawaji, Masayasu Ishiko,
Katsuhiko Nishiwaki, Toyokazu Ohnishi
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We propose a new high power insulated gate bipolar
transistor with a p-/n+ buffer
layer to improve the characteristics of high power IGBTs
used in motor control inverters during high voltage
operation. The new structure with a p- floating
layer inserted between n- epi and n+
buffer layers has a breakdown voltage higher than that
of conventional IGBT structures, without increasing
the on-voltage. We also demonstrated that with this
p- floating/n+ buffer structure,
for the first time an IGBT can have performance in the
900V-200A class.
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| P.12 |
Proposal
of Novel Collector Structure for Thin-wafer IGBTs |
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Takahide Sugiyama, Hiroyuki Ueda, Masayasu
Ishiko
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A novel collector structure for
thin-wafer IGBTs used in hybrid electric vehicles to
make a contact resistance lower without increasing turn-off
loss is proposed. This structure has a p-
Si injection layer and a p+ Ge contact. The
characteristics of a device with this new collector
structure were investigated by simulation. A 1.2kV thin-wafer
IGBT with the this p+ Ge contact layer was
fabricated, and its turn-off time and on-voltage were
measured. No remarkable increase in turn-off time was
found, in spite of a high carrier concentration in the
contact layer. Moreover, the contact resistance in the
collector of the proposed device was low, compared with
that of the conventional device. These results demonstrate
that the novel collector structure enables a low-resistivity
contact without increasing turn-off loss.
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| P.17 |
Light
Emission Analysis of Trench Gate Oxides of Power Devices
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Masanori Usui, Takahide Sugiyama,
Masayasu Ishiko, Jun Morimoto
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This paper describes the analysis
results of the trench oxide of power devices by means
of light emission analysis. Localized electron injection
was observed at the upper corners of the trench edges.
In addition, it was found that the electron injection
into the edge of trench oxide was consistently larger
than that into the center of the trench oxide during
the electrical stressing. From these results, we conclude
that the oxide shape of the upper corner of the trench
edge largely determines the reliability of the trench
gate structure.
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| P.22 |
Investigation
of Short-circuit Capability of IGBT under High Applied
Voltage Conditions |
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Tomoyuki Shoji, Masayasu Ishiko, Sachiko
Kawaji,
Takahide Sugiyama, Koji Hotta, Takeshi Fukami,
Kimimori Hamada
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We have investigated a new short-circuit
failure mode of an Insulated Gate Bipolar Transistor
(IGBT) occurring under high applied voltage, by experiments
and device simulation. The failure mode is characterized
by abrupt destruction within a few microseconds after
turning on the transistor. This phenomenon is caused
by concentration of the hole-current generated by dynamic
avalanche at an emitter contact edge of the active cells.
In addition, the hole-current path was changed by the
gate voltage. This hole-current concentration caused
sudden degradation of the short-circuit capability when
the gate voltage exceeded a certain value. By preventing
the hole-current concentration, we developed an IGBT
with sufficient short-circuit capability of more than
10μsec under a high applied voltage.
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| P.27 |
A
Novel Electro-thermal Simulation Approach to Power IGBT
Modules for Automotive Traction Applications |
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Takashi Kojima, Yasushi Yamada, Mauro
Ciappa,
Marco Chiavarini, Wolfgang Fichtner
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This paper describes a novel electro-thermal
coupling simulation technique for analyzing automotive
IGBT modules. This technique uses a electric circuit
simulator and is based on a power semiconductor device
model with temperature-dependent characteristics and
a novel compact thermal model suitable for automotive
IGBT modules. For the device model, a model parameter
definition method was proposed, and simulation results
of on-voltage characteristics using this model showed
good agreement with measurement results. The compact
thermal model can take into account lateral heat spreading
within the modules and thermal interference among power
devices. The thermal model was validated in a comparison
of temperature transient responses calculated using
the proposed model those calculated by FEM, and those
which were measured. The usefulness of the electro-thermal
coupling simulation technique was shown in example simulations
which included two parallel IGBTs with resistive load.
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