14-05-2013, 04:26 PM
MAGNETIC RAM SEMINAR REPORT
MAGNETIC RAM.docx (Size: 187.3 KB / Downloads: 19)
ABSTRACT:
Magnetic RAM (MRAM) is a new memory technology with access and cost characteristics comparable to those of conventional dynamic RAM (DRAM) and the non-volatility of magnetic media such as disk. That is MRAM retains its memory even after removing power from the device. Such a non-volatile memory has important military applications for missiles and satellites. Clearly such a device could also have important commercial applications if the non-volatility were accomplished without impacting other properties of the memory, notably density, read and write speed, and lifetime. IBM in cooperation with Infineon is promising to launch this new technology, that will eliminate the boot-up process of a computer and thus enable it to turn on as instantly as a television or radio, using memory cells based on magnetic tunnel junctions.
INTRODUCTION
You hit the power button on your television and it instantly comes to life. But do the same thing with your computer and you have to wait a few minutes while it goes through its boot up sequence. Why can't we have a computer that turns on as instantly as a television or radio? IBM, in cooperation with Infineon, is promising to launch a new technology in the next few years that will eliminate the boot-up process. Magnetic random access memory (MRAM) has the potential to store more data, access that data faster and use less power than current memory technologies. The key to MRAM is that, as its name suggests, it uses magnetism rather than electrical power to store data. This is a major leap from dynamic RAM (DRAM), the most common type of memory in use today, which requires a continuous supply of electricity and is terribly inefficient. Twenty-five years ago, DRAM overtook ferrite core memory in the race to rule the PC memory market. Now it looks like ferromagnetic technology could be making a comeback, with IBM Corp. and Infineon Technologies charging a joint team of 80 engineers and scientists with the task of making magnetic RAM (MRAM) a commercial reality within four years
ATTRACTIONS OF THIS NEW TECHNOLOGY
Consider what happens when power goes off while you are typing on your computer? Unless you are connected to an uninterruptible power supply you lose everything you were working on since you last saved the document. That's because your computer's random access memory (RAM), which stores information for fast access, can't function without power. The same goes for your cell phone and PDA. Both require a battery to keep the RAM intact with your phone numbers and personal data. But IBM researchers have developed a new form of RAM †magnetic RAM (MRAM) †that doesn't forget anything when the power goes out.
HOW MRAM WORKS
INSTANT ON COMPUTING
When you turn your computer on, you can hear it revving up. It takes a few minutes before you can actually get to programs to run. If you just want to browse the Internet, you have to wait for your computer's start-up sequence to finish before you can go to your favorite Web sites. You push the computer's power button, there's some beeping and humming, you see flashes of text on the screen and you count the seconds ticking by. It's a very slow process. Why can't it simply turn on like your television? - hit a button and instantly your Internet browser is ready to go. What is it that your computer has to do when you turn it on.
Every computer has a basic input/output system (BIOS) that performs a series of functions during the boot up sequence. The series of functions performed by BIOS includes
A power-on self-test (POST) for all of the different hardware components in the system to make sure everything is working properly
Activating other BIOS chips on different cards installed in the computer - For example, SCSI and graphics card often have their own BIOS chips.
MAGNETIC RAM ARCHITECTURE
Like Flash memory, MRAM is a non-volatile memory †a solid-state chip that has no moving parts. Unlike with DRAM chips, you don't have to continuously refresh the data on solid-state chips. Flash memory can't be used for instant-on PCs because it hasn't demonstrated long-term reliability. MRAM will likely compete with Flash memory in the portable device market for the same reason that it will replace DRAM - it reduces power consumption.
In MRAM only a small amount of electricity is needed to store bits of data. This small amount of electricity switches the polarity of each memory cell on the chip. A memory cell is created when word lines (rows) and bit lines (columns) on a chip intersect. Each one of these cells stores a 1 or a 0, representing a piece of data. MRAM promises to combine the high speed of static RAM (SRAM), the storage capacity of DRAM and the non-volatility of Flash Memory.
READING DATA
To read the bit of information stored in this memory cell, you must detennine the orientation of the two magnetic moments. Passing a small electric current directly through the memory cell accomplishes this. When the moments are parallel, the resistance of the memory cell is smaller than when the moments are not parallel. Even though there is an insulating layer between the magnetic layers, the insulating layer is so thin that electrons can "tunnel" through it from one magnetic layer to the other.
WRITING DATA
To write to the device, you pass currents through wires close to (but not connected to) the magnetic cells. Because any current through a wire generates a magnetic field, you can use this field to change the direction of the magnetic moment. The arrangement of the wires and cells is called a cross-point architecture: the magnetic junctions are set up along the intersection points of a grid. Wires called word lines run in parallel below the magnetic cells. Another set of wires called bit lines runs above the magnetic cells and perpendicular to the set of wires below. Like coordinates on a map, choosing one particular word line and one particular bit line uniquely specifies one of the memory cells. To write to a particular cell (bit), a current is passed through the two independent wires (one above and one below) that intersect at that particular cell. Only the cell at the cross point of the two wires sees the magnetic fields from both currents and changes state.
Magnetic Memory Cell Array
MRAM works by etching a grid of criss-crossing wires on a chip in two layers with the horizontal wires being placed just below the vertical wires. At each intersection, a "magnetic tunnel junction" (MTJ) is created that serves as a switch and thus as a repository for a single bit of memory. The MTJ is essentially a small magnet whose direction is easily flipped. Common materials for the MTJ include chromium dioxide and iron-cobalt alloys. Current runs perpendicularly, "tunneling" through the insulator that separates it from a sheath of copper. At the base of one of the electrodes is a fixed anti-ferromagnetic layer that creates a strong coupling field. When a magnetic field is applied, electrons flow from one electrode to another, creating 0 and 1 states.
DEVELOPING MRAM
BACKGROUND
The development of MRAM has been based on a number of significant ideas, over the past 20 years starting with Cross-tie Random Access Memory (CRAM), and then using higher sensitive giant magneto resistance (GMR) and Spin Dependent Tunneling (SDT) materials. A brief background on precursors to magneto resistive random access memory (MRAM) and then descriptions of cell configurations with improved signal levels including MRAM cells with GMR materials, cells using SDT structures
Early magnetic random access memory (as opposed to serial memories like tape and disk) used the natural hysteresis of magnetic materials to store data (T'or "0") by using two or more current carrying wires or straps. Magnetic elements were arrayed so that only ones which were to be written received a combination of magnetic fields above a write threshold, while the other elements in the array did not change storage state. Most of today's MRAM concepts still use this write technique.
MAGNETIC RAM.docx (Size: 187.3 KB / Downloads: 19)
ABSTRACT:
Magnetic RAM (MRAM) is a new memory technology with access and cost characteristics comparable to those of conventional dynamic RAM (DRAM) and the non-volatility of magnetic media such as disk. That is MRAM retains its memory even after removing power from the device. Such a non-volatile memory has important military applications for missiles and satellites. Clearly such a device could also have important commercial applications if the non-volatility were accomplished without impacting other properties of the memory, notably density, read and write speed, and lifetime. IBM in cooperation with Infineon is promising to launch this new technology, that will eliminate the boot-up process of a computer and thus enable it to turn on as instantly as a television or radio, using memory cells based on magnetic tunnel junctions.
INTRODUCTION
You hit the power button on your television and it instantly comes to life. But do the same thing with your computer and you have to wait a few minutes while it goes through its boot up sequence. Why can't we have a computer that turns on as instantly as a television or radio? IBM, in cooperation with Infineon, is promising to launch a new technology in the next few years that will eliminate the boot-up process. Magnetic random access memory (MRAM) has the potential to store more data, access that data faster and use less power than current memory technologies. The key to MRAM is that, as its name suggests, it uses magnetism rather than electrical power to store data. This is a major leap from dynamic RAM (DRAM), the most common type of memory in use today, which requires a continuous supply of electricity and is terribly inefficient. Twenty-five years ago, DRAM overtook ferrite core memory in the race to rule the PC memory market. Now it looks like ferromagnetic technology could be making a comeback, with IBM Corp. and Infineon Technologies charging a joint team of 80 engineers and scientists with the task of making magnetic RAM (MRAM) a commercial reality within four years
ATTRACTIONS OF THIS NEW TECHNOLOGY
Consider what happens when power goes off while you are typing on your computer? Unless you are connected to an uninterruptible power supply you lose everything you were working on since you last saved the document. That's because your computer's random access memory (RAM), which stores information for fast access, can't function without power. The same goes for your cell phone and PDA. Both require a battery to keep the RAM intact with your phone numbers and personal data. But IBM researchers have developed a new form of RAM †magnetic RAM (MRAM) †that doesn't forget anything when the power goes out.
HOW MRAM WORKS
INSTANT ON COMPUTING
When you turn your computer on, you can hear it revving up. It takes a few minutes before you can actually get to programs to run. If you just want to browse the Internet, you have to wait for your computer's start-up sequence to finish before you can go to your favorite Web sites. You push the computer's power button, there's some beeping and humming, you see flashes of text on the screen and you count the seconds ticking by. It's a very slow process. Why can't it simply turn on like your television? - hit a button and instantly your Internet browser is ready to go. What is it that your computer has to do when you turn it on.
Every computer has a basic input/output system (BIOS) that performs a series of functions during the boot up sequence. The series of functions performed by BIOS includes
A power-on self-test (POST) for all of the different hardware components in the system to make sure everything is working properly
Activating other BIOS chips on different cards installed in the computer - For example, SCSI and graphics card often have their own BIOS chips.
MAGNETIC RAM ARCHITECTURE
Like Flash memory, MRAM is a non-volatile memory †a solid-state chip that has no moving parts. Unlike with DRAM chips, you don't have to continuously refresh the data on solid-state chips. Flash memory can't be used for instant-on PCs because it hasn't demonstrated long-term reliability. MRAM will likely compete with Flash memory in the portable device market for the same reason that it will replace DRAM - it reduces power consumption.
In MRAM only a small amount of electricity is needed to store bits of data. This small amount of electricity switches the polarity of each memory cell on the chip. A memory cell is created when word lines (rows) and bit lines (columns) on a chip intersect. Each one of these cells stores a 1 or a 0, representing a piece of data. MRAM promises to combine the high speed of static RAM (SRAM), the storage capacity of DRAM and the non-volatility of Flash Memory.
READING DATA
To read the bit of information stored in this memory cell, you must detennine the orientation of the two magnetic moments. Passing a small electric current directly through the memory cell accomplishes this. When the moments are parallel, the resistance of the memory cell is smaller than when the moments are not parallel. Even though there is an insulating layer between the magnetic layers, the insulating layer is so thin that electrons can "tunnel" through it from one magnetic layer to the other.
WRITING DATA
To write to the device, you pass currents through wires close to (but not connected to) the magnetic cells. Because any current through a wire generates a magnetic field, you can use this field to change the direction of the magnetic moment. The arrangement of the wires and cells is called a cross-point architecture: the magnetic junctions are set up along the intersection points of a grid. Wires called word lines run in parallel below the magnetic cells. Another set of wires called bit lines runs above the magnetic cells and perpendicular to the set of wires below. Like coordinates on a map, choosing one particular word line and one particular bit line uniquely specifies one of the memory cells. To write to a particular cell (bit), a current is passed through the two independent wires (one above and one below) that intersect at that particular cell. Only the cell at the cross point of the two wires sees the magnetic fields from both currents and changes state.
Magnetic Memory Cell Array
MRAM works by etching a grid of criss-crossing wires on a chip in two layers with the horizontal wires being placed just below the vertical wires. At each intersection, a "magnetic tunnel junction" (MTJ) is created that serves as a switch and thus as a repository for a single bit of memory. The MTJ is essentially a small magnet whose direction is easily flipped. Common materials for the MTJ include chromium dioxide and iron-cobalt alloys. Current runs perpendicularly, "tunneling" through the insulator that separates it from a sheath of copper. At the base of one of the electrodes is a fixed anti-ferromagnetic layer that creates a strong coupling field. When a magnetic field is applied, electrons flow from one electrode to another, creating 0 and 1 states.
DEVELOPING MRAM
BACKGROUND
The development of MRAM has been based on a number of significant ideas, over the past 20 years starting with Cross-tie Random Access Memory (CRAM), and then using higher sensitive giant magneto resistance (GMR) and Spin Dependent Tunneling (SDT) materials. A brief background on precursors to magneto resistive random access memory (MRAM) and then descriptions of cell configurations with improved signal levels including MRAM cells with GMR materials, cells using SDT structures
Early magnetic random access memory (as opposed to serial memories like tape and disk) used the natural hysteresis of magnetic materials to store data (T'or "0") by using two or more current carrying wires or straps. Magnetic elements were arrayed so that only ones which were to be written received a combination of magnetic fields above a write threshold, while the other elements in the array did not change storage state. Most of today's MRAM concepts still use this write technique.