IEEE Power Electronics Magazine - June 2015 - 20

Production of the First IGBT
With the Welch mandate for the
development of the IGBT, I flew from
Schenectady to Cupertino, California,
in January 1981 to discuss the fabrication of the IGBT at the newly
acquired Intersil power MOSFET production facility. Although reticent to
interrupt the power MOSFET production, the manager of the production
line, Nathan Zommer, listened to my
description of the IGBT structure and
my proposed fabrication process that
would add one additional mask to
create a deep p+ region for suppression of latch-up of the parasitic thyristor. He agreed to run the IGBT in
the production line if I provided the
starting material, the mask design,
and the revised process flow.
As the acknowledged inventor and
principal developer of the device at
GE [32], I was assigned a team to support my work. Mike Adler performed
numerical simulations of the structure
that confirmed its p-i-n rectifier-like
on-state characteristics and suppression of latch-up of the parasitic thyristor using the deep p+ region. Peter
Gray performed the mask layout for
fabricating my proposed square-cell
IGBT design topology and the multiple
floating field ring edge termination
that I designed for making 600-V devices. At the same time, I designed the
n-drift region doping and thickness to
achieve the desired 600-V symmetric
blocking capability taking into account the open-base transistor breakdown. I ordered and procured the
starting material (n-drift region on p+
substrates) from vendors and supplied
them to Zommer for running the IGBT
process at Intersil. In addition, Robert
Love began to set up my IGBT process
at the GE Research Center to allow for
future device enhancements.
The first IGBT wafers from the
Intersil production line became available in August 1981. Fortunately, my
chip design was fully functional with
devices exhibiting a stable forward
blocking capability of over 600 V.
Moreover, the IGBT chips had p-i-n
rectifier-like on-state characteristics
with an on-state voltage drop of only

IEEE PowEr ElEctronIcs MagazInE

1 V at 100-200 A/cm2, vindicating my
projected performance. They also
switched on and off under the control
of a voltage pulse applied to the gate
as predicted. Latch-up in the IGBT was
observed at much higher current levels (>1,000 A/cm2) than during on-state
operation, providing good margins for
applications. However, the long turnoff tail current was a major problem
because it made the switching losses
too large for most applications.
Fortunately, I had anticipated this
issue and developed a lifetime control process for MOS-gated devices
using power MOSFETs. This built on
my work on lifetime control in p-i-n
rectifiers [33] and the understanding
of defects created by electron irradiation of silicon [34]. From this prior
experience, I knew that the defects
produced by electron irradiation in
silicon anneal out at temperatures
above 350 °C. Radiation studies on
power MOSFETs had demonstrated
large negative threshold voltage
shifts for power MOSFETs due to
charges produced in the gate oxide
by the electron irradiation. I discovered that this threshold voltage shift
could be removed by annealing the
power MOSFETs at 140 °C in a nitrogen environment while retaining the
lifetime-reducing defects in the bulk.
These results were withheld from
publication by GE until 1982 [35].
The electron irradiation process was
successfully utilized in 1981 to make
600-V IGBTs with turn-off times ranging from 17 to 0.2 ns, making these
devices useful for a broad range of
applications operating at frequencies
even above 10 kHz. This was a critical
step in making the IGBT a practical
innovation with widespread applications. During this time, my measurements also demonstrated that the
IGBT had excellent high-temperature
characteristics. These results were
withheld from publication by GE until
after December 1983 [36], [37]. Internally, this encouraged GE application
engineers to use the IGBT for controlling steam irons and space heaters
and to develop the Triad-PAR lamp
[38], among other products.

z June 2015

The IGBTs produced in the Cupertino manufacturing facility with my
electron irradiation-controlled fast
switching speed were provided to
Brock for manufacturing his adjustable-speed motor drives. In combination with a high-voltage IC for driving
the IGBTs in an H-bridge circuit, GE
was successful in launching a 5-hp
"smart switch" adjustable-speed motor drive for heat pumps on 3 October
1983. My leadership in inventing, championing, developing, and producing the
IGBT in a manufacturing line was rewarded by GE conferring the Coolidge
Fellow Award to me on 28 June 1983.
During the award ceremony, Roland
Schmitt, senior vice president and
head of the GE Research Center, stated: "We have identified nearly US$2 billion in markets that will be impacted
by the IGBT already" [39].

First IGBT Product Release
In September 1982, I was surprised to
find out that a paper titled "The Insulated Gate Transistor" was submitted
for presentation at the IEEE Industrial Applications Society Annual Meeting by Marvin Smith from the GE
Semiconductor Products Division. He
had apparently not been advised of
the embargo by Welch regarding this
technology. This event let the cat out
of the bag! GE responded by making
me first author of the paper [40] and
allowing my submission of a paper to
the IEEE IEDM conference [41]. The
1982 IEDM paper was the first report
of an IGBT device, including a 600-V
symmetric blocking structure and an
asymmetric structure with an n-buffer
layer, but I was instructed not to
show operation of the devices above
100 A/cm2. This restriction was later
removed, allowing for the publication
of IGBT device characteristics at high
current densities [42]. In conjunction
with the IEDM publication, GE put
out a press release with my photo
with the caption:
GE scientists announced development of a new power semiconductor switch called an insulated
gate rectifier, capable of operating at high current densities

Table of Contents for the Digital Edition of IEEE Power Electronics Magazine - June 2015