22-03-2014, 09:50 AM
Technical Seminar Report on OVONIC UNIFIED MEMORY
[attachment=60398]
ABSTRACT
Nowadays, digital memories are used in each and every fields of day-to-day life.
Semiconductors form the fundamental blocks of the modern electronic world providing
the brains and the memory of products all around us from washing machines to super
computers. But now we are entering an era of material limited scaling. Continuous
scaling has required the introduction of new materials.
Current memory technologies have a lot of limitations. The new memory
technologies have got all the good attributes for an ideal memory. Among them Ovonic
Unified Memory (OUM) is the most promising one. OUM is a type of nonvolatile
memory, which uses chalcogenide materials for storage of binary data. The term
chalcogen refers to the Group VI elements of the periodic table. Chalcogenide refers to
alloys containing at least one of these elements such as the alloy of germanium, antimony
and tellurium, which is used as the storage element in OUM. Electrical energy (heat) is
used to convert the material between crystalline (conductive) and amorphous (resistive)
phases and the resistive property of these phases is used to represent 0s and 1s.
To write data into the cell, the chalcogenide is heated past its melting point and
then rapidly cooled to make it amorphous. To make it crystalline, it is heated to just
below its melting point and held there for approximately 50ns, giving the atoms time to
position themselves in their crystal locations. Once programmed, the memory state of the
cell is determined by reading its resistance.
INTRODUCTION
We are now living in a world driven by various electronic equipments.
Semiconductors form the fundamental building blocks of the modern electronic world
providing the brains and the memory of products all around us from washing machines to
super computers. Semiconductors consist of array of transistors with each transistor being
a simple switch between electrical 0 and 1. Now often bundled together in their 10‟s of
millions they form highly complex, intelligent, reliable semiconductor chips, which are
small and cheap enough for proliferation into products all around us.
Identification of new materials has been, and still is, the primary means in the
development of next generation semiconductors. For the past 30 years, relentless scaling
of CMOS IC technology to smaller dimensions has enabled the continual introduction of
complex microelectronics system functions. However, this trend is not likely to continue
indefinitely beyond the semiconductor technology roadmap. As silicon technology
approaches its material limit, and as we reach the end of the roadmap, an understanding
of emerging research devices will be of foremost importance in the identification of new
materials to address the corresponding technological requirements.
HISTORY OF OVONIC UNIFIED MEMORY (OUM)
In the 1960s, Stanford R. Ovshinsky of Energy Conversion Devices first
explored the properties of chalcogenide glasses as a potential memory technology. In
1969, Charles Sie published a dissertation, at Iowa State University that both described
and demonstrated the feasibility of a phase change memory device by integrating
chalcogenide film with a diode array. A cinematographic study in 1970 established that
the phase change memory mechanism in chalcogenide glass involves electric-field-
induced crystalline filament growth. In the September 1970 issue of Electronics, Gordon
Moore co-founder of Intel published an article on the technology. However, material
quality and power consumption issues prevented commercialization of the technology.
More recently, interest and research have resumed as flash and DRAM memory
technologies are expected to encounter scaling difficulties as chip lithography shrinks.
PRESENT MEMORY TECHNOLOGY SCENARIO
As stated, revising the memory technology fields ruled by silicon technology is of
great importance. Digital Memory is and has been a close comrade of each and every
technical advancement in Information Technology. The current memory technologies
have a lot of limitations. DRAM is volatile and difficult to integrate. RAM is high cost
and volatile. Flash has slower writes and lesser number of write / erase cycles compared
to others. These memory technologies when needed to expand will allow expansion only
two-dimensional space. Hence area required will be increased. They will not allow
stacking of one memory chip over the other. Also the storage capacities are not enough to
fulfill the exponentially increasing need. Hence industry is searching for “Holy Grail”
future memory technologies that are efficient to provide a good solution. Next generation
memories are trying tradeoffs between size and cost. These make them good possibilities
for development.
EMERGING MEMORY TECHNOLOGIES
Many new memory technologies were introduced when it is understood that
semiconductor memory technology has to be replaced, or updated by its successor since
scaling with semiconductor memory reached its material limit. These memory
technologies are referred as „Next Generation Memories”. Next Generation Memories
satisfy all of the good attributes of memory. The most important one among them is their
ability to support expansion in three-dimensional spaces. Intel, the biggest maker of
computer processors, is also the largest maker of flash-memory chips is trying to combine
the processing features and space requirements feature and several next generation
memories are being studied in this perspective. They include MRAM, FeRAM, Polymer
Memory Ovonic Unified Memory, ETOX-4BPC, NRAM etc. One or two of them will
become the mainstream.
OVONIC UNIFIED MEMORY (OUM)
TECHNOLOGY
Among the above-mentioned non-volatile memories, Ovonic Unified Memory is
the most promising one. “Ovonic Unified Memory” is the registered name for the non-
volatile memory based on the material called chalcogenide.
The term “chalcogen” refers to the Group VI elements of the periodic table.
“Chalcogenide” refers to alloys containing at least one of these elements such as the alloy
of germanium, antimony, and tellurium discussed here. Energy Conversion Devices, Inc.
has used this particular alloy to develop a phase-change memory technology used in
commercially available rewriteable CD and DVD disks. This phase change technology
uses a thermally activated, rapid, reversible change in the structure of the alloy to store
data. Since the binary information is represented by two different phases of the material it
is inherently non-volatile, requiring no energy to keep the material in either of its two
stable structural states.
BASIC DEVICE OPERATION
The basic device operation can be explained from the temperature versus time
graph shown in figure 6.1. During the amorphizing reset pulse, the temperature of the
programmed volume of phase change material exceeds the melting point which
eliminates the poly crystalline order in the material. When the reset pulse is terminated
the device quenches to freeze in the disordered structural state. The quench time is
determined by the thermal environment of the device and the fall time of the pulse. The
crystallizing set pulse is of lower amplitude and of sufficient duration to maintain the
device temperature in the rapid crystallization range for a time sufficient for crystal
growth.
INTEGRATION WITH CMOS
Under contract to the Space Vehicles Directorate of the Air Force Research
Laboratory (AFRL), BAE SYSTEMS and Ovonyx began the current program in August
of 2001 to integrate the chalcogenide-based memory element into a radiation-hardened
CMOS process. The initial goal of this effort was to develop the processes necessary to
connect the memory element to CMOS transistors and metal wiring, without degrading
the operation of either the memory elements or the transistors. It also was desired to
maximize the potential memory density of the technology by placing the memory element
directly above the transistors and below the first level of metal as shown in a simplified
diagram in Figure 7.1.
CONCLUSION
Unlike conventional flash memory Ovonic unified memory can be randomly
addressed. OUM cell can be written 10 trillion times when compared with conventional
flash memory. The computers using OUM would not be subjected to critical data loss
when the system hangs up or when power is abruptly lost as are present day computers
using DRAM a/o SRAM. OUM requires fewer steps in an IC manufacturing process
resulting in reduced cycle times, fewer defects, and greater manufacturing flexibility.
These properties essentially make OUM an ideal commercial memory. Current
commercial technologies do not satisfy the density, radiation tolerance, or endurance
requirements for space applications. OUM technology offers great potential for low
power operation and radiation tolerance, which assures its compatibility in space
applications.
OUM has direct applications in all products presently using solid state
memory, including computers, cell phones, graphics-3D rendering, GPS, video
conferencing, multi-media, Internet networking and interfacing, digital TV, telecom,
PDA, digital voice recorders, modems, DVD, networking (ATM), Ethernet, and pagers.
OUM offers a way to realize full system-on-a-chip capability through integrating unified
memory, linear, and logic on the same silicon chip
[attachment=60398]
ABSTRACT
Nowadays, digital memories are used in each and every fields of day-to-day life.
Semiconductors form the fundamental blocks of the modern electronic world providing
the brains and the memory of products all around us from washing machines to super
computers. But now we are entering an era of material limited scaling. Continuous
scaling has required the introduction of new materials.
Current memory technologies have a lot of limitations. The new memory
technologies have got all the good attributes for an ideal memory. Among them Ovonic
Unified Memory (OUM) is the most promising one. OUM is a type of nonvolatile
memory, which uses chalcogenide materials for storage of binary data. The term
chalcogen refers to the Group VI elements of the periodic table. Chalcogenide refers to
alloys containing at least one of these elements such as the alloy of germanium, antimony
and tellurium, which is used as the storage element in OUM. Electrical energy (heat) is
used to convert the material between crystalline (conductive) and amorphous (resistive)
phases and the resistive property of these phases is used to represent 0s and 1s.
To write data into the cell, the chalcogenide is heated past its melting point and
then rapidly cooled to make it amorphous. To make it crystalline, it is heated to just
below its melting point and held there for approximately 50ns, giving the atoms time to
position themselves in their crystal locations. Once programmed, the memory state of the
cell is determined by reading its resistance.
INTRODUCTION
We are now living in a world driven by various electronic equipments.
Semiconductors form the fundamental building blocks of the modern electronic world
providing the brains and the memory of products all around us from washing machines to
super computers. Semiconductors consist of array of transistors with each transistor being
a simple switch between electrical 0 and 1. Now often bundled together in their 10‟s of
millions they form highly complex, intelligent, reliable semiconductor chips, which are
small and cheap enough for proliferation into products all around us.
Identification of new materials has been, and still is, the primary means in the
development of next generation semiconductors. For the past 30 years, relentless scaling
of CMOS IC technology to smaller dimensions has enabled the continual introduction of
complex microelectronics system functions. However, this trend is not likely to continue
indefinitely beyond the semiconductor technology roadmap. As silicon technology
approaches its material limit, and as we reach the end of the roadmap, an understanding
of emerging research devices will be of foremost importance in the identification of new
materials to address the corresponding technological requirements.
HISTORY OF OVONIC UNIFIED MEMORY (OUM)
In the 1960s, Stanford R. Ovshinsky of Energy Conversion Devices first
explored the properties of chalcogenide glasses as a potential memory technology. In
1969, Charles Sie published a dissertation, at Iowa State University that both described
and demonstrated the feasibility of a phase change memory device by integrating
chalcogenide film with a diode array. A cinematographic study in 1970 established that
the phase change memory mechanism in chalcogenide glass involves electric-field-
induced crystalline filament growth. In the September 1970 issue of Electronics, Gordon
Moore co-founder of Intel published an article on the technology. However, material
quality and power consumption issues prevented commercialization of the technology.
More recently, interest and research have resumed as flash and DRAM memory
technologies are expected to encounter scaling difficulties as chip lithography shrinks.
PRESENT MEMORY TECHNOLOGY SCENARIO
As stated, revising the memory technology fields ruled by silicon technology is of
great importance. Digital Memory is and has been a close comrade of each and every
technical advancement in Information Technology. The current memory technologies
have a lot of limitations. DRAM is volatile and difficult to integrate. RAM is high cost
and volatile. Flash has slower writes and lesser number of write / erase cycles compared
to others. These memory technologies when needed to expand will allow expansion only
two-dimensional space. Hence area required will be increased. They will not allow
stacking of one memory chip over the other. Also the storage capacities are not enough to
fulfill the exponentially increasing need. Hence industry is searching for “Holy Grail”
future memory technologies that are efficient to provide a good solution. Next generation
memories are trying tradeoffs between size and cost. These make them good possibilities
for development.
EMERGING MEMORY TECHNOLOGIES
Many new memory technologies were introduced when it is understood that
semiconductor memory technology has to be replaced, or updated by its successor since
scaling with semiconductor memory reached its material limit. These memory
technologies are referred as „Next Generation Memories”. Next Generation Memories
satisfy all of the good attributes of memory. The most important one among them is their
ability to support expansion in three-dimensional spaces. Intel, the biggest maker of
computer processors, is also the largest maker of flash-memory chips is trying to combine
the processing features and space requirements feature and several next generation
memories are being studied in this perspective. They include MRAM, FeRAM, Polymer
Memory Ovonic Unified Memory, ETOX-4BPC, NRAM etc. One or two of them will
become the mainstream.
OVONIC UNIFIED MEMORY (OUM)
TECHNOLOGY
Among the above-mentioned non-volatile memories, Ovonic Unified Memory is
the most promising one. “Ovonic Unified Memory” is the registered name for the non-
volatile memory based on the material called chalcogenide.
The term “chalcogen” refers to the Group VI elements of the periodic table.
“Chalcogenide” refers to alloys containing at least one of these elements such as the alloy
of germanium, antimony, and tellurium discussed here. Energy Conversion Devices, Inc.
has used this particular alloy to develop a phase-change memory technology used in
commercially available rewriteable CD and DVD disks. This phase change technology
uses a thermally activated, rapid, reversible change in the structure of the alloy to store
data. Since the binary information is represented by two different phases of the material it
is inherently non-volatile, requiring no energy to keep the material in either of its two
stable structural states.
BASIC DEVICE OPERATION
The basic device operation can be explained from the temperature versus time
graph shown in figure 6.1. During the amorphizing reset pulse, the temperature of the
programmed volume of phase change material exceeds the melting point which
eliminates the poly crystalline order in the material. When the reset pulse is terminated
the device quenches to freeze in the disordered structural state. The quench time is
determined by the thermal environment of the device and the fall time of the pulse. The
crystallizing set pulse is of lower amplitude and of sufficient duration to maintain the
device temperature in the rapid crystallization range for a time sufficient for crystal
growth.
INTEGRATION WITH CMOS
Under contract to the Space Vehicles Directorate of the Air Force Research
Laboratory (AFRL), BAE SYSTEMS and Ovonyx began the current program in August
of 2001 to integrate the chalcogenide-based memory element into a radiation-hardened
CMOS process. The initial goal of this effort was to develop the processes necessary to
connect the memory element to CMOS transistors and metal wiring, without degrading
the operation of either the memory elements or the transistors. It also was desired to
maximize the potential memory density of the technology by placing the memory element
directly above the transistors and below the first level of metal as shown in a simplified
diagram in Figure 7.1.
CONCLUSION
Unlike conventional flash memory Ovonic unified memory can be randomly
addressed. OUM cell can be written 10 trillion times when compared with conventional
flash memory. The computers using OUM would not be subjected to critical data loss
when the system hangs up or when power is abruptly lost as are present day computers
using DRAM a/o SRAM. OUM requires fewer steps in an IC manufacturing process
resulting in reduced cycle times, fewer defects, and greater manufacturing flexibility.
These properties essentially make OUM an ideal commercial memory. Current
commercial technologies do not satisfy the density, radiation tolerance, or endurance
requirements for space applications. OUM technology offers great potential for low
power operation and radiation tolerance, which assures its compatibility in space
applications.
OUM has direct applications in all products presently using solid state
memory, including computers, cell phones, graphics-3D rendering, GPS, video
conferencing, multi-media, Internet networking and interfacing, digital TV, telecom,
PDA, digital voice recorders, modems, DVD, networking (ATM), Ethernet, and pagers.
OUM offers a way to realize full system-on-a-chip capability through integrating unified
memory, linear, and logic on the same silicon chip