Download New 1700V A-Series IGBT Modules with CSTBT and

NEW 1700V A-SERIES IGBT MODULES WITHS CSTBT AND
IMPROVED FWDi
By
Nicholas Clark1, John Donlon1, Shinichi Iura2
1) Powerex Inc., Youngwood, PA, USA
2) Power Device Works, Mitsubishi Electric Corp., Fukuoka, Japan
Abstract:
This paper presents a new series of 1700V IGBT (Insulated Gate Bipolar Transistor) modules using
the new trench gate IGBT technology called Light Punch Through Carrier Stored Trench gate Bipolar
Transistor - LPT-CSTBT and an improved FWDi (Free Wheeling Diode). This new design allows the
same VCE(sat) (collector-emitter saturation voltage) at 1700V as what was available in the third
generation planar devices at 1200V given the same current rating. The current ratings of new 1700V
A-series IGBT modules are available at 500A for single switch types and from 75A to 400A for dual
switch types and are package compatible with the 1200V NF-series and 1700V KA-series.
1. Introduction
High voltage, medium current IGBT modules are widely used for industrial motor drives.
These drives have a continuous trend towards higher output power and smaller equipment
size._In response to these market needs, IGBT modules having an increased rated current
are necessary. This has led to the development of a novel series of 1700V IGBT modules
with 50% higher rated current by using a new IGBT/FWDi chip-set. This paper introduces
the structure and performance of the newly developed 1700V IGBT modules.
2. New 1700V module product range
In comparison with conventional modules, the features of the new 1700V A-series, which
have package compatibility with the conventional modules, feature:
a) 50% increased current rating in the same package size
b) Reduced IGBT losses by using the carrier stored trench gate IGBT chip technology
c) Suppressed diode oscillation by new soft reverse recovery FWDi
Fig.1 and Table 1 show a comparison between the packages used for the conventional
modules and those for the newly developed series. The new packages have the same
footprint and terminal outlines in spite of a 50% increase in rated current or conversely the
equivalent rated current in a significantly smaller package.
NEW 1700V A-SERIES IGBT MODULES WITH CSTBT AND IMPROVED FWDi
By Clark, Donlon, and Iura
Table 1: Line-up of the 1700V IGBT module
Ic
Package size (L x W)
Connection
Conventional
New
94 x 48mm
75A
Dual
—
100A
Dual
108 x 62mm
200A
Dual
300A
Dual
400A
Dual
500A
Single
2
CM75DY-34A
2
94 x 48mm
CM100DU-34KA
110 x 80mm
2
CM100DY-34A
2
2
108X62mm
CM200DY-34A
2
140x130mm
CM300DU34KA
2
140x130mm
CM400DU34KA
2
110x80mm
CM300DY-34A
2
140x130mm
CM400DY-34A
2
—
108x93mm
CM500HA-34A
Fig.1
a) CM200DY-34A
package
b) CM200DU-34KA
package
The new 1700V A-series IGBTs are available in currents from 75A to 400A in dual/chopper
switch modules and 500A in single switch modules, as shown in Table 1.
To take an example, Table 2 shows the specification of the 200A dual/chopper module.
NEW 1700V A-SERIES IGBT MODULES WITH CSTBT AND IMPROVED FWDi
By Clark, Donlon, and Iura
Table 2: Specification of 200A Module
(CM200DY-34A)
Maximum ratings:
Item
Conditions
Ratings
VCES
VGE = 0V, Tjmin Tj Tjmax
1700 V
VGES
VCE = 0V, Tjmin Tj Tjmax
± 20 V
IC
TC = 109°C
200 A
ICM
Pulse
PC
TC = 25°C
400 A
1980 W
Tj
Viso
_40 … +150°C
f=60Hz
3500 Vrms
Mass
400 g (typ.)
Electrical/Thermal characteristics:
Item
Conditions
ICES
VGE = VGES, Tj = 125°C
1 mA
VGE(th)
VCE = 10V, IC = 20mA, Tj = 25°C
7.0 V
VCE(sat)
VGE = 15V, IC = 200A, Tj = 125°C
2.45 V
VEC
VGE = 0V, IC = 200A, Tj = 125°C
3.0 V
Eon
VCC = 1000V, IC = 200A
LS = 100nH, VGE = ±15V
RG =2.4 Eoff
Typical
94 mJ/P
59 mJ/P
53 mJ/P
Erec
Rth(j-c)Q
IGBT part
0.063 K/W
Rth(j-c)R
Diode part
0.11 K/W
3. Chip technology
3-1. IGBT chip technology
The newly developed 1700V A-series IGBT modules are based on our new trench gate chip
technology called “Light Punch Through Carrier Stored Trench gate Bipolar Transistor” or
LPT-CSTBT. The features of LPT-CSTBT are as follows.
a) Trench gate & Carrier stored structure
b) Light punch through structure
NEW 1700V A-SERIES IGBT MODULES WITH CSTBT AND IMPROVED FWDi
By Clark, Donlon, and Iura
G
E
p base
n+ emitter
VMOS
Carrier stored layer
Vdiode
n- layer
n+?@
buffer layer
p + substrate
VCE (sat) = VMOS + Vdiode
C
Fig.2: Cross section of LPT-CSTBT
a) Trench
Gate & Carrier Stored Structure
IGBT chips used in modules with high power ratings need to be optimized for low losses and
higher current density in order to increase the current rating. This reduction of losses is
achieved by using the LPT-CSTBT chip technology. The development and features of this
chip technology are explained in detail in references [1] and [2].
The cross section of the LPT-CSTBT is shown in Fig.2. The on-state voltage of the IGBT,
VCE (sat) = VMOS + Vdiode. The VMOS is the voltage drop of the MOSFET portion between p
base and n+ emitter and can be reduced by the trench gate structure. The Vdiode is the voltage
drop of the diode portion between p+ substrate and n_ layer. It can be reduced by the carrier
stored layer structure. As a result, the rated current of the LPT-CSTBT is increased in spite of
decreasing the active chip area compared to the conventional planar IGBT design (see Fig.3)
[1,2].
b) Light punch through (LPT) structure
The new 1200V CSTBT chip utilizes an optimized vertical structure based on Mitsubishi’s
Light Punch-Through (LPT) technology. A schematic comparison of conventional NPT,
Epitaxial PT, and LPT chips is shown in Fig. 4. The key to the LPT structure is an optimized
n- drift region that it is thin enough to provide low VCE(sat) while maintaining a robust
switching SOA. An n buffer layer is utilized to secure a sufficiently high breakdown voltage
and low leakage current in the presence of the optimally thin n- drift region. The thickness of
the n- drift layer is selected so that the depletion region extends to the collector when rated
voltage is applied in the off-state. However, at normal operating voltages the depletion
region does not reach the buffer layer giving an operation characteristic similar to
conventional NPT designs. Another feature of the LPT structure is optimized n+ buffer and p
NEW 1700V A-SERIES IGBT MODULES WITH CSTBT AND IMPROVED FWDi
By Clark, Donlon, and Iura
collector layers that provide controlled carrier concentration in the n- region during
conduction. The result is efficient switching characteristics without the need for carrier
lifetime control processing. The new CSTBT chips are fabricated from low cost n-type single
crystal (nonepitaxial) wafer material. [5]
The LPT structure has the advantage of wide SOA and positive temperature coefficient of
VCE (sat). Another advantage of LPT is its narrow VCE (sat) distribution, since no lifetime
control in n- bulk is required. [1,2]
200
Rated current of chip [A]
Planer IGBT
LPT-CSTBT
150
100
50
0
0
50
100
150
Active chip area [mm
200
250
2]
Fig.3: Comparison of the relationship between active chip area and rated collector current of LPTCSTBT versus conventional planar IGBT
Fig.4: Comparison of Structures
NEW 1700V A-SERIES IGBT MODULES WITH CSTBT AND IMPROVED FWDi
By Clark, Donlon, and Iura
3-2. Diode Chip Technology
IGBT modules need an anti-parallel, emitter to collector free-wheel diode to ensure that
reverse voltage does not appear across the IGBT chip. Oscillations of current and voltage
often can be observed in a conventional diode, especially during reverse recovery at low
current. The oscillation may cause EMI problems for both the module itself or for the
converter equipment. In order to suppress such oscillation, an optimized soft recovery diode
is needed. The newly designed diode has optimized carrier density to soften the reverse
recovery behavior.
P
N
—— : conventional
—— : new diode
N+
Fig.5: Comparison of carrier density profile between conventional diode and new one
The carrier density profile of the conventional diode and that of the new one are compared in
Fig.5. The hole injection is suppressed by reduced carrier density in the P layer and the N+
layer.
4. Electrical performance
The new 1700V IGBT modules with LPT-CSTBT have improved static and dynamic
electrical characteristics as described below.
4-1. Static characteristics
The modules use a number of positive temperature coefficient LPT-CSTBT chips in parallel
in order to realize the high module current rating. The positive temperature coefficient
prevents temperature and current imbalance between modules connected in parallel as well as
between the parallel chips inside the module.
NEW 1700V A-SERIES IGBT MODULES WITH CSTBT AND IMPROVED FWDi
By Clark, Donlon, and Iura
The VCE (sat) of the new modules with LPT-CSTBT is about 35% lower than the
conventional one. Furthermore, the trade-off characteristic _ the relationship between VCE
(sat) and turn-off switching energy, Eoff _ of LPT-CSTBT is significantly improved compared
with conventional planar 1700V IGBT modules.
7
6
Vce (sat) [V]
5
4
3
2
CM200DY34A
CM200DU-34KA
1
0
0
100
200
Ic [A]
300
400
Fig.6: Output characteristics (typical) of 200A
(CM200DY-34A & CM200DU-34KA)
[Tj=125°C, VGE=15V]
4-2. Dynamic characteristics
The new 1700V A-series IGBT module has excellent dynamic performance in comparison
with the conventional one. In the same operating conditions of di/dt and gate drive, turn-on
and turn-off switching energy, Eon and Eoff, of the new 1700V IGBT modules are about 12%
and 8% lower than those of conventional one as shown in Table 2 and Table 3.
Table 2: Turn-on switching characteristics
Item
Conventional module
CM200DU-34KA
New module
CM200DY-34A
di/dt
1000 A/s
1000 A/s
Eon
106 mJ
94 mJ
[Tj=125°C, VCC=1000V, IC=200A, VGE=±15V, Inductive load]
Table 3: Turn-off switching characteristics
Item
Conventional module
CM200DU-34KA
New module
CM200DU-34A
di/dt
250 A/s
250 A/s
Eoff
64 mJ
59 mJ
[Tj=125°C, VCC=1000V, IC=200A, VGE=±15V, Inductive load]
NEW 1700V A-SERIES IGBT MODULES WITH CSTBT AND IMPROVED FWDi
By Clark, Donlon, and Iura
The total IGBT losses in inverter operation can be estimated from the above electrical (static
and dynamic) characteristics and compared with the conventional modules (see Fig.7). The
losses are reduced by 32% when using the new modules.
700
@ Tj=125°C, Io=140A
rms , Vcc=850V, fc=5kHz, p.f.=0.8
Static
600
Dynamic
500
400
207
300
32%
reduced
134
200
100
283
198
0
CM200DU-34KA
CM200DY-34A
Fig.7: Comparison of IGBT inverter losses
4-3. Short circuit performance
In general, modules with trench gate IGBT chips tend to have quite high short circuit currents
because of the trench IGBT’s large saturation current density. However, the new modules
have suppressed such excessive short circuit currents by introducing an optimized trench cell
design which maintains the 10s short-circuit withstand time. [1]
5. Package structure
One key issue in power module assembly technology is wire bonding. The new modules use
LPT-CSTBT IGBTs which have a higher current density due to the increase module current
rating. If the conventional wire bonding technique is applied to LPT-CSTBT the wire
temperature may become high. Such high wire temperature is a disadvantageous
phenomenon for power cycling capability. Therefore, a new wire bonding technique has been
introduced to suppress this temperature increase.
Fig.8 shows a compared top view of IGBT chip temperature including bond wires with an
infrared camera and includes a simple cross section depiction of the wire bonding: a) is the
conventional wire bonding applied to an LPT-CSTBT chip and b) is the new wire bonding
technique. As Fig.8 shows, the wire temperature of new IGBT module is about 12K lower
than the conventional one under the same loading conditions. The improvement points of the
new wire bonding technique are:
- lower wire current density due to increased number of bond wires;
NEW 1700V A-SERIES IGBT MODULES WITH CSTBT AND IMPROVED FWDi
By Clark, Donlon, and Iura
- non-cutting (“stitch”) bonding technique (see red circle in Fig.11) to decrease current
density at bond sites.
By using this new stitch wire bonding technique the temperature excursion is reduced and the
power cycling capability of new modules is improved.
a)
b)
Wire temperature:
110 °C maximum
Wire temperature:
98 °C maximum
Fig.8: Comparison of wire temperature between stitch and no stitch technique
a) Conventional wire bonding technique on LPT-CSTBT chip
(no stitch wire technique)
b) New wire bonding technique on LPT-CSTBT chip
(with stitch wire technique)
6. Conclusion
A new series of high current 1700V IGBT modules using new LPT-CSTBT has been
introduced. Improved loss performance allows a 50% increase in rated module current while
keeping package compatibility with the previous module generation.
7. References
[1] K. Nakamura, S. Kusunoki, H. Nakamura, Y. Ishimura, Y, Tomomatsu, T. Minato,
“Advanced Wide Cell Pitch CSTBTs Having Light Punch-Through (LPT) Structures”,
ISPSD 2002
[2] J. Yamada, S. Sasaki, T. Matsuoka, Y. Ishimura, Y. Tomomatsu, I. Merfert, E. Thal
“Next Generation High Power Dual IGBT Module with CSTBT Chip and Package
Concept”, PCIM Europe 2002
[3] K. Satoh, T. Nakagawa, K. Morishita, S. Koga, A. Kawakami, “4.5kV Soft Recovery
Diode with Carrier Stored Structure”, ISPSD 1998
[4] S. Iura, E. Suekawa, K. Morishita, M. Koga, E. Thal, “New 1700V IGBT Modules with
CSTBT”, PCIM Europe 2004
[5] Junji Yamada, Yoshiharu Yu, Y. Ishimura, John F. Donlon, Eric R. Motto, “Low Turnoff Switching Energy 1200V IGBT Module”, IAS 2002