MRAM
Encyclopedia
Magnetoresistive Random-Access Memory is a non-volatile
computer memory
(NVRAM
) technology that has been under development since the 1990s. Continued increases in density of existing memory technologies – notably flash RAM and DRAM
– kept it in a niche role in the market, but its proponents believe that the advantages are so overwhelming that magnetoresistive RAM will eventually become dominant for all types of memory, becoming a true universal memory
.
or current flows, but by magnetic
storage elements. The elements are formed from two ferromagnetic plates, each of which can hold a magnetic field, separated by a thin insulating layer. One of the two plates is a permanent magnet set to a particular polarity, the other's field can be changed to match that of an external field to store memory. This configuration is known as a spin valve
and is the simplest structure for a MRAM bit
. A memory device is built from a grid of such "cells".
The simplest method of reading is accomplished by measuring the electrical resistance
of the cell. A particular cell is (typically) selected by powering an associated transistor
that switches current
from a supply line through the cell to ground. Due to the magnetic tunnel effect, the electrical resistance
of the cell changes due to the orientation of the fields in the two plates. By measuring the resulting current, the resistance inside any particular cell can be determined, and from this the polarity of the writable plate. Typically if the two plates have the same polarity this is considered to mean "1", while if the two plates are of opposite polarity the resistance will be higher and this means "0".
Data is written to the cells using a variety of means. In the simplest, each cell lies between a pair of write lines arranged at right angles to each other, above and below the cell. When current is passed through them, an induced magnetic field
is created at the junction, which the writable plate picks up. This pattern of operation is similar to core memory, a system commonly used in the 1960s. This approach requires a fairly substantial current to generate the field, however, which makes it less interesting for low-power uses, one of MRAM's primary disadvantages. Additionally, as the device is scaled down in size, there comes a time when the induced field overlaps adjacent cells over a small area, leading to potential false writes. This problem, the half-select (or write disturb) problem, appears to set a fairly large size for this type of cell. One experimental solution to this problem was to use circular domains written and read using the giant magnetoresistive effect
, but it appears this line of research is no longer active.
Another approach, the toggle mode, uses a multi-step write with a modified multi-layer cell. The cell is modified to contain an "artificial antiferromagnet" where the magnetic orientation alternates back and forth across the surface, with both the pinned and the free layers, consisting of multi-layer stacks isolated by a thin "coupling layer". The resulting layers have only two stable states, which can be toggled from one to the other by timing the write current in the two lines so one is slightly delayed, thereby "rotating" the field. Any voltage less than the full write level actually increases its resistance to flipping. That means that other cells located along one of the write lines will not suffer from the half-select problem, allowing for smaller cell sizes.
A newer technique, spin-transfer torque (STT) or Spin Transfer Switching, uses spin-aligned ("polarized") electron
s to directly torque the domains. Specifically, if the electrons flowing into a layer have to change their spin, this will develop a torque that will be transferred to the nearby layer. This lowers the amount of current needed to write the cells, making it about the same as the read process. There are concerns that the "classic" type of MRAM cell will have difficulty at high densities due to the amount of current needed during writes, a problem STT avoids. For this reason, the STT proponents expect the technique to be used for devices of 65 nm and smaller. The downside is the need to maintain the spin coherence. Overall, the STT requires much less write current than conventional or toggle MRAM. Research in this field indicates that STT current can be reduced up to 50 times by using a new composite structure. However, higher speed operation still requires higher current.
Other potential arrangements include "Thermal Assisted Switching
" (TAS-MRAM), which briefly heats up (reminiscent of phase-change memory
) the magnetic tunnel junctions during the write process and keeps the MTJs stable at a colder temperature the rest of the time; and "vertical transport MRAM" (VMRAM), which uses current through a vertical column to change magnetic orientation, a geometric arrangement that reduces the write disturb problem and so can be used at higher density.
DRAM uses a small capacitor
as a memory element, wires to carry current to and from it, and a transistor to control it – referred to as a "1T1C" cell. This makes DRAM the highest-density RAM currently available, and thus the least expensive, which is why it is used for the majority of RAM found in a computer.
MRAM is physically similar to DRAM in makeup, although often does not require a transistor for the write operation. However, as mentioned above, the most basic MRAM cell suffers from the half-select problem, which limits cell sizes to around 180 nm or more. Toggle-mode MRAM offers a much smaller size before this becomes a problem, apparently around 90 nm, the same size as most current DRAM products. To be worth putting into wide production, however, it is generally believed that MRAM will have to move to the 65 nm size of the most advanced memory devices, which will require the use of STT.
In contrast, MRAM never requires a refresh. This means that not only does it retain its memory with the power turned off but also there is no constant power-draw. While the read process in theory requires more power than the same process in a DRAM, in practice the difference appears to be very close to zero. However, the write process requires more power in order to overcome the existing field stored in the junction, varying from three to eight times the power required during reading. Although the exact amount of power savings depends on the nature of the work – more frequent writing will require more power – in general MRAM proponents expect much lower power consumption (up to 99% less) compared to DRAM. STT-based MRAMs eliminate the difference between reading and writing, further reducing power requirements.
It is also worth comparing MRAM with another common memory system, flash RAM. Like MRAM, flash does not lose its memory when power is removed, which makes it very common as a "hard disk replacement" in small devices such as digital audio players or digital camera
s. When used for reading, flash and MRAM are very similar in power requirements. However, flash is re-written using a large pulse of voltage (about 10 V) that is stored up over time in a charge pump
, which is both power-hungry and time-consuming. In addition, the current pulse physically degrades the flash cells, which means flash can be written only to some finite number of times before it must be replaced.
In contrast, MRAM requires only slightly more power to write than read, and no change in the voltage, eliminating the need for a charge pump. This leads to much faster operation, lower power consumption, and an indefinitely long "lifetime".
performance is limited by the rate at which the charge stored in the cells can be drained (for reading) or stored (for writing). MRAM operation is based on measuring voltages rather than charges or currents, so there is less "settling time" needed. IBM researchers have demonstrated MRAM devices with access times on the order of 2 ns, somewhat better than even the most advanced DRAMs built on much newer processes. A team at the German Physikalisch-Technische Bundesanstalt
have demonstrated MRAM devices with 1 ns settling times, better than the currently accepted theoretical limits for DRAM, although the demonstration was a single cell. The differences compared to flash are far more significant, with write times as much as thousands of times faster.
The only current memory technology that easily competes with MRAM in terms of performance is static RAM, or SRAM. SRAM consists of a series of transistors arranged in a flip-flop
, which will hold one of two states as long as power is applied. Since the transistors have a very low power requirement, their switching time is very low. However, since an SRAM cell consists of several transistors, typically four or six, its density is much lower than DRAM. This makes it expensive, which is why it is used only for small amounts of high-performance memory, a notable one being the CPU cache
in almost all modern CPU designs.
Although MRAM is not quite as fast as SRAM, it is close enough to be interesting even in this role. Given its much higher density, a CPU designer may be inclined to use MRAM to offer a much larger but somewhat slower cache, rather than a smaller but faster one. It remains to be seen how this trade-off will play out in the future.
, and flash. This also explains the huge amount of research being carried out into developing it.
However, to date, MRAM has not been widely adopted in the market. It may be that vendors are not prepared to take the risk of allocating a modern fab to MRAM production when such fabs cost upwards of a few billion dollars to build and can instead generate revenue by serving developed markets producing flash and DRAM memories.
The very latest fabs seem to be used for flash, for example producing 16 Gbit parts produced by Samsung
on a 50 nm process. Slightly older fabs are being used to produce most DDR2 DRAM, most of which is produced on a one-generation-old 90 nm process rather than using up scarce leading-edge capacity.
In comparison, MRAM is still largely "in development", and being produced on older non-critical fabs. The only commercial product widely available at this point is Everspin
's 4 Mbit part, produced on a several-generations-old 180 nm process. As demand for flash continues to outstrip supply, it appears that it will be some time before a company can afford to "give up" one of their latest fabs for MRAM production. Even then, MRAM designs currently do not come close to flash in terms of cell size, even using the same fab.
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2011
Non-volatile memory
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, in the most basic sense, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer...
computer memory
Computer storage
Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is one of the core functions and fundamental components of computers....
(NVRAM
NVRAM
Non-volatile random-access memory is random-access memory that retains its information when power is turned off, which is described technically as being non-volatile...
) technology that has been under development since the 1990s. Continued increases in density of existing memory technologies – notably flash RAM and DRAM
Dram
Dram or DRAM may refer to:As a unit of measure:* Dram , an imperial unit of mass and volume* Armenian dram, a monetary unit* Dirham, a unit of currency in several Arab nationsOther uses:...
– kept it in a niche role in the market, but its proponents believe that the advantages are so overwhelming that magnetoresistive RAM will eventually become dominant for all types of memory, becoming a true universal memory
Universal memory
Universal memory may mean:* any memory device combining cost benefits of DRAM, speed of SRAM, and non-volatility of flash memory** magnetoresistive random-access memory ** Bubble memory** Racetrack memory** ferroelectric random-access memory...
.
Description
Unlike conventional RAM chip technologies, in MRAM data is not stored as electric chargeElectric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...
or current flows, but by magnetic
Magnetism
Magnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...
storage elements. The elements are formed from two ferromagnetic plates, each of which can hold a magnetic field, separated by a thin insulating layer. One of the two plates is a permanent magnet set to a particular polarity, the other's field can be changed to match that of an external field to store memory. This configuration is known as a spin valve
Spin valve
A spin valve is a device consisting of two or more conducting magnetic materials, that alternates its electrical resistance depending on the alignment of the magnetic layers, in order to exploit the Giant Magnetoresistive effect. The magnetic layers of the device align "up" or "down" depending on...
and is the simplest structure for a MRAM bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
. A memory device is built from a grid of such "cells".
The simplest method of reading is accomplished by measuring the electrical resistance
Electrical resistance
The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical...
of the cell. A particular cell is (typically) selected by powering an associated transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
that switches current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
from a supply line through the cell to ground. Due to the magnetic tunnel effect, the electrical resistance
Electrical resistance
The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical...
of the cell changes due to the orientation of the fields in the two plates. By measuring the resulting current, the resistance inside any particular cell can be determined, and from this the polarity of the writable plate. Typically if the two plates have the same polarity this is considered to mean "1", while if the two plates are of opposite polarity the resistance will be higher and this means "0".
Data is written to the cells using a variety of means. In the simplest, each cell lies between a pair of write lines arranged at right angles to each other, above and below the cell. When current is passed through them, an induced magnetic field
Electromagnetic induction
Electromagnetic induction is the production of an electric current across a conductor moving through a magnetic field. It underlies the operation of generators, transformers, induction motors, electric motors, synchronous motors, and solenoids....
is created at the junction, which the writable plate picks up. This pattern of operation is similar to core memory, a system commonly used in the 1960s. This approach requires a fairly substantial current to generate the field, however, which makes it less interesting for low-power uses, one of MRAM's primary disadvantages. Additionally, as the device is scaled down in size, there comes a time when the induced field overlaps adjacent cells over a small area, leading to potential false writes. This problem, the half-select (or write disturb) problem, appears to set a fairly large size for this type of cell. One experimental solution to this problem was to use circular domains written and read using the giant magnetoresistive effect
Giant magnetoresistive effect
Giant magnetoresistance is a quantum mechanical magnetoresistance effect observed in thin-film structures composed of alternating ferromagnetic and non-magnetic layers...
, but it appears this line of research is no longer active.
Another approach, the toggle mode, uses a multi-step write with a modified multi-layer cell. The cell is modified to contain an "artificial antiferromagnet" where the magnetic orientation alternates back and forth across the surface, with both the pinned and the free layers, consisting of multi-layer stacks isolated by a thin "coupling layer". The resulting layers have only two stable states, which can be toggled from one to the other by timing the write current in the two lines so one is slightly delayed, thereby "rotating" the field. Any voltage less than the full write level actually increases its resistance to flipping. That means that other cells located along one of the write lines will not suffer from the half-select problem, allowing for smaller cell sizes.
A newer technique, spin-transfer torque (STT) or Spin Transfer Switching, uses spin-aligned ("polarized") electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s to directly torque the domains. Specifically, if the electrons flowing into a layer have to change their spin, this will develop a torque that will be transferred to the nearby layer. This lowers the amount of current needed to write the cells, making it about the same as the read process. There are concerns that the "classic" type of MRAM cell will have difficulty at high densities due to the amount of current needed during writes, a problem STT avoids. For this reason, the STT proponents expect the technique to be used for devices of 65 nm and smaller. The downside is the need to maintain the spin coherence. Overall, the STT requires much less write current than conventional or toggle MRAM. Research in this field indicates that STT current can be reduced up to 50 times by using a new composite structure. However, higher speed operation still requires higher current.
Other potential arrangements include "Thermal Assisted Switching
Thermal Assisted Switching
Thermal Assisted Switching, or TAS, is one of the new 2nd generation approaches to MRAM currently being developed. A few different designs have been proposed, but all rely on the idea of reducing the required switching fields by heating...
" (TAS-MRAM), which briefly heats up (reminiscent of phase-change memory
Phase-change memory
Phase-change memory is a type of non-volatile computer memory. PRAMs exploit the unique behavior of chalcogenide glass. Heat produced by the passage of an electric current switches this material between two states, crystalline and amorphous...
) the magnetic tunnel junctions during the write process and keeps the MTJs stable at a colder temperature the rest of the time; and "vertical transport MRAM" (VMRAM), which uses current through a vertical column to change magnetic orientation, a geometric arrangement that reduces the write disturb problem and so can be used at higher density.
Density
The main determinant of a memory system's cost is the density of the components used to make it up. Smaller components, and fewer of them, mean that more "cells" can be packed onto a single chip, which in turn means more can be produced at once from a single silicon wafer. This improves yield, which is directly related to cost.DRAM uses a small capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
as a memory element, wires to carry current to and from it, and a transistor to control it – referred to as a "1T1C" cell. This makes DRAM the highest-density RAM currently available, and thus the least expensive, which is why it is used for the majority of RAM found in a computer.
MRAM is physically similar to DRAM in makeup, although often does not require a transistor for the write operation. However, as mentioned above, the most basic MRAM cell suffers from the half-select problem, which limits cell sizes to around 180 nm or more. Toggle-mode MRAM offers a much smaller size before this becomes a problem, apparently around 90 nm, the same size as most current DRAM products. To be worth putting into wide production, however, it is generally believed that MRAM will have to move to the 65 nm size of the most advanced memory devices, which will require the use of STT.
Power consumption
Since the capacitors used in DRAM lose their charge over time, memory assemblies that use DRAM must refresh all the cells in their chips approximately 20 times a second, reading each one and re-writing its contents. As DRAM cells decrease in size, the refresh cycles become shorter, and the power-draw more continuous.In contrast, MRAM never requires a refresh. This means that not only does it retain its memory with the power turned off but also there is no constant power-draw. While the read process in theory requires more power than the same process in a DRAM, in practice the difference appears to be very close to zero. However, the write process requires more power in order to overcome the existing field stored in the junction, varying from three to eight times the power required during reading. Although the exact amount of power savings depends on the nature of the work – more frequent writing will require more power – in general MRAM proponents expect much lower power consumption (up to 99% less) compared to DRAM. STT-based MRAMs eliminate the difference between reading and writing, further reducing power requirements.
It is also worth comparing MRAM with another common memory system, flash RAM. Like MRAM, flash does not lose its memory when power is removed, which makes it very common as a "hard disk replacement" in small devices such as digital audio players or digital camera
Digital camera
A digital camera is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. It is the main device used in the field of digital photography...
s. When used for reading, flash and MRAM are very similar in power requirements. However, flash is re-written using a large pulse of voltage (about 10 V) that is stored up over time in a charge pump
Charge pump
A charge pump is a kind of DC to DC converter that uses capacitors as energy storage elements to create either a higher or lower voltage power source. Charge pump circuits are capable of high efficiencies, sometimes as high as 90–95% while being electrically simple circuits.Charge pumps use some...
, which is both power-hungry and time-consuming. In addition, the current pulse physically degrades the flash cells, which means flash can be written only to some finite number of times before it must be replaced.
In contrast, MRAM requires only slightly more power to write than read, and no change in the voltage, eliminating the need for a charge pump. This leads to much faster operation, lower power consumption, and an indefinitely long "lifetime".
Performance
DRAMDram
Dram or DRAM may refer to:As a unit of measure:* Dram , an imperial unit of mass and volume* Armenian dram, a monetary unit* Dirham, a unit of currency in several Arab nationsOther uses:...
performance is limited by the rate at which the charge stored in the cells can be drained (for reading) or stored (for writing). MRAM operation is based on measuring voltages rather than charges or currents, so there is less "settling time" needed. IBM researchers have demonstrated MRAM devices with access times on the order of 2 ns, somewhat better than even the most advanced DRAMs built on much newer processes. A team at the German Physikalisch-Technische Bundesanstalt
Physikalisch-Technische Bundesanstalt
The Physikalisch-Technische Bundesanstalt is based in Braunschweig and Berlin. It is the national institute for natural and engineering sciences and the highest technical authority for metrology and physical safety engineering in Germany....
have demonstrated MRAM devices with 1 ns settling times, better than the currently accepted theoretical limits for DRAM, although the demonstration was a single cell. The differences compared to flash are far more significant, with write times as much as thousands of times faster.
The only current memory technology that easily competes with MRAM in terms of performance is static RAM, or SRAM. SRAM consists of a series of transistors arranged in a flip-flop
Flip-flop (electronics)
In electronics, a flip-flop or latch is a circuit that has two stable states and can be used to store state information. The circuit can be made to change state by signals applied to one or more control inputs and will have one or two outputs. It is the basic storage element in sequential logic...
, which will hold one of two states as long as power is applied. Since the transistors have a very low power requirement, their switching time is very low. However, since an SRAM cell consists of several transistors, typically four or six, its density is much lower than DRAM. This makes it expensive, which is why it is used only for small amounts of high-performance memory, a notable one being the CPU cache
CPU cache
A CPU cache is a cache used by the central processing unit of a computer to reduce the average time to access memory. The cache is a smaller, faster memory which stores copies of the data from the most frequently used main memory locations...
in almost all modern CPU designs.
Although MRAM is not quite as fast as SRAM, it is close enough to be interesting even in this role. Given its much higher density, a CPU designer may be inclined to use MRAM to offer a much larger but somewhat slower cache, rather than a smaller but faster one. It remains to be seen how this trade-off will play out in the future.
Overall
MRAM has similar performance to SRAM, similar density of DRAM but much lower power consumption than DRAM, and is much faster and suffers no degradation over time in comparison to flash memory. It is this combination of features that some suggest make it the "universal memory", able to replace SRAM, DRAM, EEPROMEEPROM
EEPROM stands for Electrically Erasable Programmable Read-Only Memory and is a type of non-volatile memory used in computers and other electronic devices to store small amounts of data that must be saved when power is removed, e.g., calibration...
, and flash. This also explains the huge amount of research being carried out into developing it.
However, to date, MRAM has not been widely adopted in the market. It may be that vendors are not prepared to take the risk of allocating a modern fab to MRAM production when such fabs cost upwards of a few billion dollars to build and can instead generate revenue by serving developed markets producing flash and DRAM memories.
The very latest fabs seem to be used for flash, for example producing 16 Gbit parts produced by Samsung
Samsung
The Samsung Group is a South Korean multinational conglomerate corporation headquartered in Samsung Town, Seoul, South Korea...
on a 50 nm process. Slightly older fabs are being used to produce most DDR2 DRAM, most of which is produced on a one-generation-old 90 nm process rather than using up scarce leading-edge capacity.
In comparison, MRAM is still largely "in development", and being produced on older non-critical fabs. The only commercial product widely available at this point is Everspin
Freescale Semiconductor
Freescale Semiconductor, Inc. is a producer and designer of embedded hardware, with 17 billion semiconductor chips in use around the world. The company focuses on the automotive, consumer, industrial and networking markets with its product portfolio including microprocessors, microcontrollers,...
's 4 Mbit part, produced on a several-generations-old 180 nm process. As demand for flash continues to outstrip supply, it appears that it will be some time before a company can afford to "give up" one of their latest fabs for MRAM production. Even then, MRAM designs currently do not come close to flash in terms of cell size, even using the same fab.
History
Most of the following has been taken from mram-info web site:- 1955 - Magnetic core memoryMagnetic core memoryMagnetic-core memory was the predominant form of random-access computer memory for 20 years . It uses tiny magnetic toroids , the cores, through which wires are threaded to write and read information. Each core represents one bit of information...
had the same reading writing principle as MRAM - 1988 - European scientists (Albert FertAlbert FertAlbert Fert is a French physicist and one of the discoverers of giant magnetoresistance which brought about a breakthrough in gigabyte hard disks...
and Peter GrünbergPeter GrünbergPeter Andreas Grünberg is a German physicist, and Nobel Prize in Physics laureate for his discovery with Albert Fert of giant magnetoresistance which brought about a breakthrough in gigabyte hard disk drives.-Biography:...
) discovered the "giant magnetoresistive effectGiant magnetoresistive effectGiant magnetoresistance is a quantum mechanical magnetoresistance effect observed in thin-film structures composed of alternating ferromagnetic and non-magnetic layers...
" in thin-film structures. - 1995 - Motorola (later to become Freescale) initiates work on MRAM development
- 2000 - IBM and Infineon established a joint MRAM development program.
- 2000 - Spintec laboratory's first Spin Torque TransferSpin Torque TransferSpin-transfer torque is an effect in which the orientation of a magnetic layer in a tunnel magnetoresistance or spin valve can be modified using a spin-polarized current....
patent. - 2002 - NVE Announces Technology Exchange with Cypress Semiconductor.
- 2003 - A 128 kbit MRAM chip was introduced, manufactured with a 180 nm lithographic process
2004
- June - Infineon unveiled a 16-Mbit prototype, manufactured with a 180 nm lithographic process
- September - MRAM becomes a standard product offering at Freescale.
- October - Taiwan developers of MRAM tape out 1 Mbit parts at TSMCTSMCTaiwan Semiconductor Manufacturing Company, Limited or TSMC is the world's largest dedicated independent semiconductor foundry, with its headquarters and main operations located in the Hsinchu Science Park in Hsinchu, Taiwan.-Overview:...
. - October - Micron drops MRAM, mulls other memories.
- December - TSMC, NECNEC, a Japanese multinational IT company, has its headquarters in Minato, Tokyo, Japan. NEC, part of the Sumitomo Group, provides information technology and network solutions to business enterprises, communications services providers and government....
, Toshiba describe novel MRAM cells. - December - Renesas Technology trumpets a high performance, high-reliability MRAM technology.
- Spintech laboratory's first observation of Thermal Assisted SwitchingThermal Assisted SwitchingThermal Assisted Switching, or TAS, is one of the new 2nd generation approaches to MRAM currently being developed. A few different designs have been proposed, but all rely on the idea of reducing the required switching fields by heating...
(TAS) as MRAM approach. - Crocus TechnologyCrocus TechnologyCrocus Technology, founded in 2004, is a venture-capital-backed semiconductor startup company developing next generation magnetoresistive random access memory technology. The company's products originated in a Grenoble-based Spintec laboratory...
is founded; the company is a developer of second-generation MRAM
2005
- January - Cypress SemiconductorCypress SemiconductorCypress Semiconductor Corporation is a Silicon Valley-based semiconductor design and manufacturing company founded by T. J. Rodgers and others from Advanced Micro Devices. It was formed in 1982 with backing by Sevin Rosen and went public in 1986. The company initially focused on the design and...
samples MRAM, using NVE IP. - March - Cypress to Sell MRAM Subsidiary.
- June - Honeywell posts data sheet for 1-Mbit rad-hard MRAM using a 150 nm lithographic process
- August - MRAM record: memory cell runs at 2 GHz.
- November - Renesas Technology and Grandis collaborate on development of 65 nm MRAM employing spin torque transferSpin torque transferSpin-transfer torque is an effect in which the orientation of a magnetic layer in a tunnel magnetoresistance or spin valve can be modified using a spin-polarized current....
(STT). - November - NVE receives an SBIR grant to research cryptographic tamper-responsive memory.
- December - SonySony, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
announced the first lab-produced spin-torque-transfer MRAM, which utilizes a spin-polarized current through the tunneling magnetoresistance layer to write data. This method consumes less power and is more scalable than conventional MRAM. With further advances in materials, this process should allow for densities higher than those possible in DRAM. - December - Freescale Semiconductor Inc. demonstrates an MRAM that uses magnesium oxide, rather than an aluminum oxide, allowing for a thinner insulating tunnel barrier and improved bit resistance during the write cycle, thereby reducing the required write current.
- Spintec laboratory gives Crocus Technology exclusive license on its patents.
Current status
2006- February - ToshibaToshibais a multinational electronics and electrical equipment corporation headquartered in Tokyo, Japan. It is a diversified manufacturer and marketer of electrical products, spanning information & communications equipment and systems, Internet-based solutions and services, electronic components and...
and NEC announced a 16 Mbit MRAM chip with a new "power-forking" design. It achieves a transfer rate of 200 MB/s, with a 34 ns cycle time - the best performance of any MRAM chip. It also boasts the smallest physical size in its class — 78.5 square millimeters — and the low voltage requirement of 1.8 volts. - July - On July 10, Austin Texas - Freescale Semiconductor begins marketing a 4-Mbit MRAM chip, which sells for approximately $25.00 per chip.
2007
- R&D moving to spin transfer torqueSpin Torque TransferSpin-transfer torque is an effect in which the orientation of a magnetic layer in a tunnel magnetoresistance or spin valve can be modified using a spin-polarized current....
RAM (SPRAM) - February - Tohoku University and Hitachi developed a prototype 2 Mbit Non-Volatile RAM Chip employing spin-transfer torque switching.
- August - "IBM, TDK Partner In Magnetic Memory Research on Spin Transfer Torque Switching" IBM and TDK to lower the cost and boost performance of MRAM to hopefully release a product to market.
- November - Toshiba applied and proved the spin transfer torque switching with perpendicular magnetic anisotropy MTJ device.
- November - NEC Develops World's Fastest SRAM-Compatible MRAM With Operation Speed of 250 MHz.
2008
- Japanese satellite, SpriteSat, to use Freescale MRAM to replace SRAM and FLASH components
- June - Samsung and Hynix become partner on STT-MRAM http://www.eetasia.com/ART_8800531562_480200_NT_cf6338bb.HTM
- June - Freescale spins off MRAM operations as new company Everspin http://everspin.com/PDF/press/2008_june9_Everspin%20Release.pdf
- August - Scientists in Germany have developed next-generation MRAM that is said to operate as fast as fundamental performance limits allow, with write cycles under 1 nanosecond.
2009
- June - Hitachi and Tohoku University demonstrated a 32-Mbit spin-transfer torque RAM (SPRAM).http://www.vlsisymposium.org/circuits/cir_abstract/8-4.htm
- June - Crocus TechnologyCrocus TechnologyCrocus Technology, founded in 2004, is a venture-capital-backed semiconductor startup company developing next generation magnetoresistive random access memory technology. The company's products originated in a Grenoble-based Spintec laboratory...
and Tower Semiconductor announce deal port Crocus' MRAM process technology to Tower's manufacturing environment
2010
- June - Hitachi and Tohoku Univ announced Multi-level SPRAM http://techon.nikkeibp.co.jp/english/NEWS_EN/20100622/183658/
2011
- March - PTB, Germany, announces having achieved a below 500 ps (2GBit/s) write cycle
Applications
Proposed uses for MRAM include devices such as:- AerospaceAerospaceAerospace comprises the atmosphere of Earth and surrounding space. Typically the term is used to refer to the industry that researches, designs, manufactures, operates, and maintains vehicles moving through air and space...
and military systems - Digital cameraDigital cameraA digital camera is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. It is the main device used in the field of digital photography...
s - NotebooksLaptopA laptop, also called a notebook, is a personal computer for mobile use. A laptop integrates most of the typical components of a desktop computer, including a display, a keyboard, a pointing device and speakers into a single unit...
- Smart cardSmart cardA smart card, chip card, or integrated circuit card , is any pocket-sized card with embedded integrated circuits. A smart card or microprocessor cards contain volatile memory and microprocessor components. The card is made of plastic, generally polyvinyl chloride, but sometimes acrylonitrile...
s - Mobile telephones
- Cellular base stations
- Personal ComputerPersonal computerA personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
s - Battery-Backed SRAM replacement
- Datalogging specialty memories (black boxFlight data recorderA flight data recorder is an electronic device employed to record any instructions sent to any electronic systems on an aircraft. It is a device used to record specific aircraft performance parameters...
solutions) - Media players
- Book readers
See also
- Magnetic bubble memory
- EEPROMEEPROMEEPROM stands for Electrically Erasable Programmable Read-Only Memory and is a type of non-volatile memory used in computers and other electronic devices to store small amounts of data that must be saved when power is removed, e.g., calibration...
- FeRAMFerroelectric RAMFerroelectric RAM is a random-access memory similar in construction to DRAM but uses a ferroelectric layer instead of a dielectric layer to achieve non-volatility. FeRAM is one of a growing number of alternative non-volatile memory technologies that offer the same functionality as Flash memory...
- FerromagnetismFerromagnetismFerromagnetism is the basic mechanism by which certain materials form permanent magnets, or are attracted to magnets. In physics, several different types of magnetism are distinguished...
- MagnetoresistanceMagnetoresistanceMagnetoresistance is the property of a material to change the value of its electrical resistance when an external magnetic field is applied to it. The effect was first discovered by William Thomson in 1856, but he was unable to lower the electrical resistance of anything by more than 5%. This...
- MemristorMemristorMemristor is a passive two-terminal electrical component envisioned by Leon Chua as a fundamental non-linear circuit element relating charge and magnetic flux linkage...
- NRAMNano-RAMNano-RAM is a proprietary computer memory technology from the company Nantero. It is a type of nonvolatile random access memory based on the mechanical position of carbon nanotubes deposited on a chip-like substrate. In theory, the small size of the nanotubes allows for very high density memories...
- nvSRAMNvSRAMnvSRAM is a type of non-volatile computer memory. It is similar in operation to SRAMs. The current market for non volatile memory is dominated by BBSRAMs, or Battery Backed Static Random Access Memory. However, BBSRAMs are slow and suffer from ROHS compliance issues...
- Phase-change memoryPhase-change memoryPhase-change memory is a type of non-volatile computer memory. PRAMs exploit the unique behavior of chalcogenide glass. Heat produced by the passage of an electric current switches this material between two states, crystalline and amorphous...
(PRAM) - MOSFETMOSFETThe metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
- Spin valveSpin valveA spin valve is a device consisting of two or more conducting magnetic materials, that alternates its electrical resistance depending on the alignment of the magnetic layers, in order to exploit the Giant Magnetoresistive effect. The magnetic layers of the device align "up" or "down" depending on...
- Tunnel magnetoresistanceTunnel magnetoresistanceThe Tunnel magnetoresistance is a magnetoresistive effect that occurs in magnetic tunnel junctions . This is a component consisting of two ferromagnets separated by a thin insulator. If the insulating layer is thin enough , electrons can tunnel from one ferromagnet into the other...
- Spin transfer torque
- Freescale SemiconductorFreescale SemiconductorFreescale Semiconductor, Inc. is a producer and designer of embedded hardware, with 17 billion semiconductor chips in use around the world. The company focuses on the automotive, consumer, industrial and networking markets with its product portfolio including microprocessors, microcontrollers,...
- Crocus TechnologyCrocus TechnologyCrocus Technology, founded in 2004, is a venture-capital-backed semiconductor startup company developing next generation magnetoresistive random access memory technology. The company's products originated in a Grenoble-based Spintec laboratory...
External links
- www.mram-info.com, a clearinghouse of MRAM industry news
- IBM research - MRAM By Richard Butner
- Science magazine article from April, 2005
- Science magazine article from September, 2005
- Wired News article from February, 2006
- NEC Press Release from February, 2006
- BBC news article from July, 2006
- Freescale MRAM - an in-depth examination from August 2006
- MRAM – The Birth of the Super Memory - An article and an interview with Freescale about their MRAM technology
- Spin torque applet - An applet illustrating the principles underlying spin-torque transfer MRAM
- New Speed Record for Magnetic Memories - The Future of ThingsThe Future of ThingsThe Future of Things is an online magazine covering diverse topics related to science and technology. The magazine was launched in 2006.-History:...
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