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Trends of Semiconductor Technology for Total System Solutions
48
Trends of Semiconductor Technology for Total System
Solutions
OVERVIEW: Recent progress in electronics technology has been remarkable.
Progress in electronics overall has been supported by semiconductor
technology with the information equipment field, as typified by multimedia,
but one leading example. The semiconductor technology that makes
implementation of a system on chip possible has contributed both to higher
levels of system performance and also to the creation of new product
concepts. To respond to user requirements for future higher-level
performance and faster development speed, finer-pattern processing
technology and advanced semiconductor device technology are of course
needed. Moreover proposals for total system solutions are needed including
higher-performance microprocessors and application technology such as
middleware; also system LSI technology and package technology
Masao Hotta
Shoji Shukuri
Koichi Nagasawa
INTRODUCTION
PROGRESS in semiconductor technology in typical
products such as memories and microprocessors has
enabled the electronics industry to achieve remarkable
growth (Fig. 1). For example, in the early 1970s
personal computer performance was only 0.1 million
instructions per second (MIPS), but recently it has
exceeded 100 MIPS, for an improvement of more than
4 orders of magnitude. The driving force behind the
higher performance of electronic equipment has been
the evolution of semiconductor technology, especially
the higher density and higher speed made possible by
finer-pattern processes.
As finer-pattern technology progresses, and deep
submicron processes become a reality, the scale of the
number of circuits that can be integrated on a single
chip rapidly increases. Many subsystems can be
fabricated on the same piece of silicon, and the system-
Next-generation
mobile telephone
Higher performance and smaller size
Handheld computer
Middleware
Design technology
MPEG camera
Digital camera
Personal computer
System LSI
Video camera
Year
MPEG: Moving Picture Experts Group
Fig. 1—Semiconductor
Technology Suppports Systems
Solutions.
LSI processing performance
has improved remarkably as
higher integration and device
performance enabled by
semiconductor technology
paves the way to multiple
functional modules on a chip.
This not only contributes to
improved performance of
system products but also
extends to the creation of newconcept products.
Hitachi Reviw Vol. 48 (1999), No. 2
49
HDD PRML read-channel LSI
AGC
Filter
ADC
Transfer rate (MHz)
Encoderdecoder
Equalizer
Viterbi
decoder
AGC : automatic gain control
ADC : anlog-to-digital converter
PRML : partial response maximum
likelihood
1,000
HDD PRML read-channel LSI
320 Mbit/s
240 Mbit/s
130 Mbit/s
100
90 Mbit/s
10
1994
1996
1998
2000
Year
on-chip era has arrived. A system on chip doesn’t
merely consist of the integration of a large-scale digital
circuit such as a microprocessor, but also includes the
integration of a large number of other functions
including flash memory, dynamic random access
memory (DRAM), and analog circuits.
The system user can freely select among
semiconductor devices in seeking the optimum
configuration of a system product, and the semiconductor manufacturer is required to propose a solution
meeting these requirements. Thus it is necessary to
have the macromodules and software required by users,
and to provide the technical skills needed to use these
to efficiently design system LSIs. In this paper we
will discuss the semiconductor technology that
supports systems solutions and its future trend.
EXPECTATIONS FOR SYSTEMS
SOLUTIONS
Now that large-scale multifunctional-circuits can
be fabricated on a silicon chip, and all circuits
comprising a board-level system can be fabricated on
a single LSI as a system on chip, the following benefits
are newly realized.
(1) Improved system performance resulting from
reduced delay time and power consumption.
(2) Smaller system products resulting from reduced
assembly area.
(3) Elimination of pinout bottleneck and implementation of new architectures with on-chip flash memory
and analog circuits.
Fig. 2—HDD Read Channel Trend.
High-speed operation has been implemented by
integrating analog circuits, A-D converter circuits,
and Viterbi decoder circuits on a single chip.
(4) New concept products utilizing the characteristics
above.
A read-channel LSI that is a signal processing LSI
for a hard disk drive (HDD) is an example of the
benefits in (1) above. This LSI amplifies the signal
from the magnetic head and regenerates the digital
waveform. But as the signal frequency increases with
higher recording densities, the filter processing of the
readout signal becomes more complex.
High-speed performance and low power consumption have been realized by implementing on a single
chip analog circuits, analog-to-digital (A-D)
conversion circuits, and a Viterbi decoder — which
performs digital filter processing. Hitachi, Ltd. used
0.4-µm process complementary metal-oxide semiconductor (CMOS) technology to fabricate a read-channel
LSI with a top world-level transfer rate of 240 Mbit/s
and a power consumption of only 1 W1) (Fig 2).
As an example of (3) and (4) above, a Moving Picture Experts Group (MPEG) camera can be cited.2) This
mobile device uses the international standard MPEG
technology to compress and decompress full-motion
video to record full-motion video on a hard disk or
flash memory rather than the formerly-used magnetic
tape. Because tape is not used the camera can not
only be made small, but also connectivity with a
personal computer is excellent, and a total digital image
environment can be built from input through output.
Thus a new product concept has been created.
A technical background important to the realization
of this MPEG camera is the MPEG1 compression and
Trends of Semiconductor Technology for Total System Solutions
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1.000
RISC: reduced instruction set computer
New-generation RISC
Processing performance (MIPS)
Alpha*1
SH-4
300
PentiumPro*3
StrorongArm*1
Pentium*3
100
Power
PC*2
Power PC602
SH-3
ARM7500
SH-2
SH-1
Personal computer/workstation
80486
10
1
2
* 1 StrongArm and Alpha are trademarks of
Digital Equipment Corp. of the U.S.
* 2 Power PC 603 is a trademark in the U.S.
of International Business Machines
Corp. of the U.S.
* 3 Pentium and Pentium Pro are trademarks
of Intel Corp. of the U.S.
5
10
20
Power consumption (W)
decompression LSI. It is implemented with about
200,000 logic gates and a total of 32-kbit static random
access memory (SRAM) as a large-scale LSI that has
a power consumption of only 0.5 W. This LSI can be
said to be a system solution that contributes to the
creation of a new product concept.
SEMICONDUCTOR DEVICE TECHNOLOGY
SUPPORTS HIGHER-PERFORMANCE
SYSTEMS
Microprocessor Trends and CMOS Technology
The microprocessor is a key device supporting
system solutions. Increased processor performance
provides greater solution breadth. For conversion to a
system on chip, though, processing performance alone
is insufficient and lower power consumption and
smaller size are important. These requirements are
especially important for products such as mobile
information devices and multimedia devices.
Thus Hitachi, Ltd. developed the SuperH RISC
microprocessor series implementing low power
consumption together with high-speed processing.
Products in this series can be classified as a new
generation of processors that differ from former
processors that emphasized processing performance
(Fig. 2). The recently developed SH-4 achieves a
processing performance of 360 MIPS with a power
consumption of a mere 1.5 W, and it supports extended
capabilities such as decompression of compressed
images and graphics processing.
CMOS semiconductor technology is the basic
50
Fig. 3—New-Generation Microprocessors
Featuring Improved Processing Performance at
Low Power Consumption.
New-generation processors have emerged
featuring excellent processing performance at low
power consumption and small size in response to
system-on-chip requirements.
technology used to implement these excellent
processors with this high processing performance-topower consumption ratio. In general, the propagation
delay time td of CMOS logic is inversely proportional
to the saturation current — maximum transistor
operating current. Thus it is necessary to increase
saturation current Ids to make td smaller. However,
reducing power supply voltage Vdd is an effective
method of reducing power consumption, and much
progress has been made in the development on
semiconductor devices that attain high saturation
currents at low power supply voltages.
Fig.4 shows the shift in saturation current for unit
gate width with power supply voltage normalized. As
can be seen in the figure, saturation current has
increased with progress in fine patterning, and the trend
should continue in the future. Saturation current is
continuing to increase with semiconductor device
development, including use of nitride films as the gate
insulation layer and use of a nonuniform channel
doping distribution structure.
Embedded Technology
Embedded DRAM technology
The market for logic with embedded DRAM is
evolving in a polarized manner. One facet is highspeed high-density semiconductor devices for personal
computer graphics and car navigation systems, while
the other facet is low power consumption semiconductor devices for mobile information devices such
as video cameras and digital still cameras. Hitachi
Hitachi Reviw Vol. 48 (1999), No. 2
51
Gate insulating film thickness Tox(nm)
1.5
2
3
4
5
7
12
700
Vdd=1.2 – 0.9 V
1.5 – 1.2 V
2006
500
1.8 – 1.5 V
400
2003
300
2.5 – 1.8 V
1999
200
3.3 V
1997
100
5V
1994
1991
0
0
0.1
has adopted 0.18-µm 256-Mbit general-purpose
DRAM memory technology to develop the embedded
DRAM logic HG75M used mainly in graphics
applications, and is now developing the HG76M using
the higher-density 0.14-µm process.
The most difficult technology problem in
embedded DRAM is maintaining the heat resistance
of the logic devices that form the substrate during the
capacitor process. To achieve the same logic device
performance as in pure logic devices, it is imperative
to use a low-temperature capacitor process that has
absolutely no impact on the underlying logic devices.
The tantalum oxide film (Ta205) capacitor technology
developed by Hitachi is suitable for low-temperature
processing, and it can be said to open the path to
implementation of large-capacity embedded DRAM
LSIs.
Embedded flash memory technology
Hitachi has since 1993 developed flexible zero
turnaround time (FZTAT) single-chip microcomputers
with on-chip flash memory to reduce product cycle
time of consumer electronics and personal computer
peripheral products; and to meet the needs of the
mobile device market for smaller size, lighter weight,
and thinner profile. The relationship between flash
module capacity and readout time is shown in Fig. 5.
To keep up with the rapid pace in the increase of
microprocessor clock frequencies, a readout frequency
greater than 100 MHz is imperative for 0.2-µm
products operating at 1.8 volts.
It will be difficult for peripheral devices to attain
0.2
0.3
0.4
0.5
0.6
Gate length (µm)
low voltage and high-speed readout merely by finerpattern technology. Other factors will be important
including high-speed boost of the readout block
together with optimization of drivers and mat structure.
Moreover, increased size of the voltage step-up circuit
at 1.8 V is a problem.
Also becoming a problem is the writing method
adopted in memory cells used in FZTAT
microcomputers beyond 0.5 µm: Writing by extracting
110
90
Readout frequency (MHz)
Fig. 4—Improvement in the
Saturation Current of CMOS
Devices (nMOS Transistors).
Even at low current and voltage,
improvement in the MOS transistor
saturation current that determines
the speed of CMOS logic circuits
increases current drawn.
Saturation current Ids/Vdd (µA/[Vµm])
600
0.2 µ[email protected] V
70
0.35 µm@3 V
50
30
5V
3.3 V
10
0
100
0.6 µm
200
300
400
Module capacity (kbyte)
500
600
Fig. 5—Flash Module Readout Speed vs Capacity for
Microcomputers with On-Chip Flash Memory.
Readout frequencies above 100 MHz are said to be necessary
for 0.2-µm products to keep pace with higher-speed
microcomputers.
Trends of Semiconductor Technology for Total System Solutions
electrons by tunnel current from the floating gate is
becoming disadvantageous with smaller-size memory
cells. Other modes of operation including hot electron
injection methods should be considered, as should
operation modes enabling low voltage operation
together with high-speed writing and erasing.
High-Frequency Semiconductor Device
Technology
Even in the mobile telephone field, system LSIs
have been developed with the integration of highfrequency processing LSIs including mixers and
modulator-demodulators implemented using 0.6-µm
bipolar CMOS (Bi-CMOS) technology. Finer
patterning in CMOS processes is leading to higher
frequency capabilities, and devices made with CMOS
beyond 0.35 µm are now able to operate adequately at
frequencies up to 2 GHz. Thus in the near future,
single-chip LSI solutions will be feasible in addition
to the CMOS baseband processing circuits already
implemented.
Low-cost Si high-frequency power MOS fieldeffect transistors (MOSFET) having characteristics
well-suited to mass production are now being
fabricated by fine-pattern MOS LSI technology,
leading to extremely rapid improvement in highfrequency perfromance. Since they are readily
adaptable to single power supply operation and power
control is easily realized, they are being widely used
in cellular phones for the European standard - Global
System for Mobile Communications (GSM).
A GSM radio frequency (rf) module using a highfrequency power MOSFETs recently developed by
Hitachi realizes an overall efficiency greater than 47%
at a maximum power output of 4 W when operated
from a 3.6-V power supply. Since all circuits can be
implemented in silicon MOS, future implementation
of a single-chip mobile telephone is no longer a dream.
Design Technology Supporting HigherPerformance Systems
52
consumption. However decreasing the power supply
voltage reduces the saturation current that is an
indication of driving capability, and causes a decrease
in logic circuit speed.
Decreasing the threshold voltage is an effective
method of avoiding these problems, but then leakage
current increases. It thus becomes necessary to employ
a method of holding down the leakage current in
mobile devices to reduce power consumption during
standby. The typical method used is the technique of
increasing the transistor substrate voltage during
standby to change the threshold voltage. With this
technology, logic circuit power can be lowered to 1/2
to 1/10 without degrading speed, while leakage current
can be reduced to about 1/1,000.
Mixed analog technology
To meet the requirements on system LSIs for an
increasingly larger number of functions, there are
strong demands for integration of analog circuits such
as A-D converters and filters on a single chip with
digital circuits. The biggest problem when integrating
precision analog circuits with digital circuits is the
effect of noise from the digital circuits on the analog
circuits. CMOS circuits have a large logic amplitude,
and affect the small-signal analog circuits through
power supply lines or the substrate, resulting in
degradation of the analog-circuit signal-to-noise (S/
N) ratio.
For example, the noise induced into the input of an
A-D converter circuit with about 7-k gates reaches
about 10 - 20 mV. This effect can be reduced by
methods such as shifting the clocks of the digital
circuits and A-D converter circuit or by employing the
analog circuits for fully differential operation. These
techniques can reduce the effect of noise to 1/10 to 1/
30.
Hitachi employed the technologies described to
develop as a product the 73C series cell-based IC on
which a 10-bit 20-MHz A-D converter can be fabricated.
Low-power high-speed circuit design technology
As the number of transistors fabricated on a chip
increases, and the operating frequency increases to
provide higher-speed processing, the power
consumption increases abruptly, but there are strong
requirements for low power consumption in the mobile
device field. The power consumption of CMOS logic
circuits is proportional to the square of the power
supply voltage, though, so decreasing the power supply
voltage is an effective method of lowering the power
System design support technology
Fabrication of a system on chip has been made
possible by the rapid increase in the number of
transistor that can be fabricated on a single chip.
However, as the scale of ICs to be designed becomes
larger, there tends to be a large increase in the number
of development personnel and development time. A
method of solving this problem now being tested is
the reuse of design assets in an evolving approach
Hitachi Reviw Vol. 48 (1999), No. 2
called intellectual property (IP). That is, functional
blocks - macromodules - are standardized and
reciprocally used among different design sections and
enterprises to shorten design time and reduce design
cost to achieve higher design efficiency.
Moreover software (middleware) is necessary to
operate functional blocks such as CPUs and digital
signal processors (DSP), and this software is necessary
when providing a system solution. Image processing
middleware such as MPEG and Joint Photographic
Experts Group (JPEG) products are available.
Moreover Hitachi has developed a variety of
middleware products including those for voice
processing, voice synthesis, voice recognition, and
communications functions.
CONCLUSIONS
In this paper we discussed the trends of
semiconductor technology that support system
solutions. We have high expectations for
semiconductor technology in providing technology
solutions for more complex and higher-performance
systems products. For the future, progress in
semiconductor process technology and semiconductor
device technology will lead to higher levels of
integration and performance, with larger numbers of
functional modules on a single chip. We foresee LSI
functionality making remarkable advances to become
the driving force in the creation of totally new product
categories
We will continue to endeavor to put our full energy
into the development of total semiconductor
technology including design technology and
middleware. Our aim is to respond to user requirements by continuing to provide system solutions.
53
REFERENCES
(1) T. Matsuura, et al., “A 240 Mb/s 1W CMOS EPRML Read
Channel LSI for Hard Disc Drives,” ISSCC 1998, SP24.5
(2) T. Imaide, et al., “MPEG Cameras and Video Information
Systems,” The Hitachi Hyoron 79 (1997) pp.637-642
(3) K. Irie et al., 2.7 V Single-Chip GSM RF Transceiver IC,
ISSCC1997, Sa18.2
(4) K. M. Fukuda, et al., Voltage-Comparator-Based Measurement
of Equivalently Sampled Substrate Noise Waveforms in MixedSignal Integrated Circuits, IEEE JSSC, Vol.31, No.5(1996-5)
ABOUT THE AUTHORS
IMasao Hotta
Entered Hitachi, Ltd. in 1976, and now works at the
Advanced Device Development Dept., Semiconductor
Technology Development Center, Semiconductor &
Integrated Circuits Group. He is currently engaged in
the development of advanced LSIs. Mr. Hotta ia a
member of IEEE., and can be reached by e-mail at
[email protected].
Shoji Shukuri
Entered Hitachi, Ltd. in 1982, and now works at the
Process Technology Development Dept.,
Semiconductor Technology Development Center,
Semiconductor & Integrated Circuits Group. He is
currently engaged in the development of new
semiconductor processes. Mr. Shukuri can be reached
by e-mail at [email protected].
Koichi Nagasawa
Entered Hitachi, Ltd. in 1970, and now works at the
Semiconductor Technology Development Center,
Semiconductor & Integrated Circuits Group. He is
currently engaged in the development of new
semiconductor processes. Mr. Nagawasa is a
member of IEEE., and can be reached by e-mail at
[email protected].