Magnetic Random Access Memory (MRAM)
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MagneticMagnetic RandomRandom AccessAccess MemoryMemory (MRAM)(MRAM) Jimmy Zhu ABB Professor in Engineering Department of Electrical and Computer Engineering Carnegie Mellon University 24 August 2004 ComputerComputer SystemSystem TLB CPU SRAM L1 Cache SRAM SRAM L2 Cache Volatile Memory DRAMDRAM Main Memory Archival Memory Non-Volatile Memory Disk Drive J. Zhu, 18-200 Lecture, Fall 2004 2 1 Static RAM (SRAM) Cache Memory Fast: 6-Transistor CMOS SRAM Access time: < 1 ns = 10-9 second Expensive: $100 / MByte Low Density: >120 F2 F -- minimum fabrication feature size J. Zhu, 18-200 Lecture, Fall 2004 3 Field Effect Transistor (FET) Conducting metal plate Gate Insulating oxide layer D Source Drain G n+ p n+ Semiconductor S Conducting ground symbol n-channel FET MOSFET: Metal-Oxide-semiconductor-FET J. Zhu, 18-200 Lecture, Fall 2004 4 2 How a FET Works: Transistor On http://www.pbs.org/transistor/science/info/transmodern.html Active condition: electron with charge –e VGS > VT i.e. G Gate VGG > VT VGG + + + + + + + + Drain i D + + D n n S p D G RD Source S VDD n-channel FET Drain current will I D be a function of gate voltage. VDD J. Zhu, 18-200 Lecture, Fall 2004 5 How a FET Works: Transistor Off electron with charge –e Cutoff condition: V < V Gate GS T G VT threshold voltage S Drain n+ n+ V = V p D DD Source D D G RD S VDD No current Zero Drain current. J. Zhu, 18-200 Lecture, Fall 2004 6 3 AA ModernModern CMOSCMOS ProcessProcess VDD M2 V Vin out M1 gate-oxide TiSi2 AlCu SiO2 Tungsten poly p-well n-well SiO2 n+ p-epi p+ Dual-Well Trench-Isolatedp+ CMOS Process J. Zhu, 18-200 Lecture, Fall 2004 7 DynamicDynamic RAMRAM Main Computer Memory Q State “1” V = ¾ Individual access time 60 ns C + + + + + + + ¾ 10 F2 State “0” V = 0 − − − − − − − ¾ $4 /MByte ¾ All “1”s need to be refreshed every 1 ms. J. Zhu, 18-200 Lecture, Fall 2004 8 4 Rotational Latency 7,500 – 15,000 rpm track sector Inexpensive: $0.001/1MByte Rotational Latency • Average latency: 3 – 6 ms • Wait until desired sector passes under head • Worst case: a complete rotation 7,500 rpm = 8 ms 15,000 rpm = 4 ms J. Zhu, 18-200 Lecture, Fall 2004 9 Hard Disk Drives 18-316 Introduction to Data Storage 18-517 Data Storage Systems Design Magnetic Force Microscopy Image of A Disk Surface J. Zhu, 18-200 Lecture, Fall 2004 10 5 PricePrice vs.vs. SpeedSpeed 100 SRAM 10 DRAM 1 0.1 0.01 Price ($)Per MByte HDD 1E-3 1E-9 1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 Access Time (second) J. Zhu, 18-200 Lecture, Fall 2004 11 ComputerComputer SystemSystem onon aa Chip?Chip? Can one change the disk drive into a high speed memory chip? If one can, one can put the entire computer system on a single chip: TLB CPU SRAM SRAMSRAM DRAMDRAM Disk Drive J. Zhu, 18-200 Lecture, Fall 2004 12 6 Magnetic RAM: Historical Perspective Motorola 4Mbits MRAM Chip Magnetic tunnel junction 2003 Honeywell 16Kbits MRAM Chip AMR Technology 1994 Control Data Corp. 1Kbits Ferrite Core Memory 1965 J. Zhu, 18-200 Lecture, Fall 2004 13 RememberRemember MagnetMagnet !! Magnetic moment can maintain its direction without power ! J. Zhu, 18-200 Lecture, Fall 2004 14 7 Memory Element Magnetic Tunnel Junction (MTJ) Magnetic electrode State “0” State “1” m1 Tunnel barrier m2 Magnetic electrode 2.5 CoFe/Al2O3 (7-20Å) /Co 2.0 ) Ω 1.5 1.0 Resistance (k 0.5 0.0 0 20 40 60 80 100 Data Bits J. Zhu, 18-200 Lecture, Fall 2004 15 MemoryMemory ArrayArray “L” “L”“H” “L” “L” “L” “H” “L” J. Zhu, 18-200 Lecture, Fall 2004 16 8 Detailed Structure State “0” State “1” Magnetic moments are fixed. Only the magnetic moment of a storage layer is switched back and forth. J. Zhu, 18-200 Lecture, Fall 2004 17 WritingWriting BitsBits State “0”I State “1” I r r I M M r H M State “1” H State “0” J. Zhu, 18-200 Lecture, Fall 2004 18 9 X-PointX-Point AddressingAddressing y x I half-select elements I 2 / 3 2 / 3 2 / 3 1.0 H k = H x + H y ) k 0.5 0.0 -0.5 Y-Component Field (H Field Y-Component -1.0 -1.0 -0.5 0.0 0.5 1.0 X-Compone Field (Hk) J. Zhu, 18-200 Lecture, Fall 2004 19 MRAM Cell J. Zhu, 18-200 Lecture, Fall 2004 20 10 44 MbitsMbits MRAMMRAM ChipChip Freescale 4Mbits MRAM Chip J. Zhu, 18-200 Lecture, Fall 2004 21 MRAM:MRAM: DreamDream Memory?Memory? Advantages of MRAM: 9 Nonvolatile (No power needed to maintain memory states) 9 SRAM Speed (~ 1 nanosecond ) 9 DRAM Density (~ 20 F2 ) 9 Endurance (Infinitely rewritable) MRAM has the potential to be an universal memory to replace SRAM, DRAM, FLASH, and disk drives in some applications to become the Universal Solid-State Memory! J. Zhu, 18-200 Lecture, Fall 2004 22 11 AA PotentialPotential GameGame ChangerChanger If MRAM replaces SRAM, DRAM or even disk drives: ¾ Instant on systems: No booting from disk drive ¾ Minimum stand-by power (Turn it off!) ¾ Enable computer system to be integrated on a single chip! J. Zhu, 18-200 Lecture, Fall 2004 23 Applications J. Zhu, 18-200 Lecture, Fall 2004 24 12 System on Chip (SoC) Example: SoC Function Module Computing (processing) RF Module Memory Data Processing NV Memory Memory J. Zhu, 18-200 Lecture, Fall 2004 25 MRAM: Dream Memory? Present MRAM Technology Shortfalls: Relatively high power dissipation (high current) Down-size scaling not clear (thermal magnetic stability) J. Zhu, 18-200 Lecture, Fall 2004 26 13 X-PointX-Point AddressingAddressing y x I half-select elements I 2 / 3 2 / 3 2 / 3 1.0 H k = H x + H y ) k 0.5 0.0 99.999% of power is dissipated -0.5 2 as I R on the write lines! (H Field Y-Component -1.0 -1.0 -0.5 0.0 0.5 1.0 X-Compone Field (Hk) J. Zhu, 18-200 Lecture, Fall 2004 27 Magnetic Cladding (18-303 Electromagnetics) Word Line with ¾ The main power consumption Cladding arises from the ohmic dissipation, I2R, in word/digital lines. Digital Line with cladding Read Transistor x 5 J. Zhu, 18-200 Lecture, Fall 2004 28 14 Thermally Activated Reversal Hx τrise= 0.3 ns 0.1 µm 0 H x = 0.8H x 2 ns t 0.2 µm E Angle J. Zhu, 18-200 Lecture, Fall 2004 29 The Potential Universal Memory SRAM DRAM Disk Drive FLASH MRAM Speed Density Cyclability Cost Non-volatility Power consumption J. Zhu, 18-200 Lecture, Fall 2004 30 15 Conclusions MRAM: The enabling technology for computer systems on a single chip! Only Continued Innovation Will Ensure Future Competitiveness of MRAM J. Zhu, 18-200 Lecture, Fall 2004 31 Data Storage Systems Track Fundamentals of E.E. 18-220 Eng. Electromagnetics Intro. to Data Storage Tech. 18-303 18-316 18-396 Signal & Sys. 18-517 Data Storage Sys. Design Physics of Appl. Magn. 18-715 Advanced Appl. Magn. 18-716 J. Zhu, 18-200 Lecture, Fall 2004 32 16 18-517 Data Storage Systems Design BuildingBuilding aa VirtualVirtual DiskDisk DriveDrive usingusing MATLAB/SIMULINKMATLAB/SIMULINK Data to be recorded Retrieved signal Equalizer Recovered data Detector J. Zhu, 18-200 Lecture, Fall 2004 33 18-315 Fall 2004 Introduction to Optical Communication Systems Professor Jimmy Zhu [email protected] Course Objective: Provide a basic understanding of present optical communication systems and components, as well as future engineering challenges. J. Zhu, 18-200 Lecture, Fall 2004 34 17 Bandwidth Explosion Source: Agilent Technologies 1P 100T 10T Video on demand O.S. 1T 100G Voice-centric DWDM 10G Network World wide web WDM 1G Doubles every 4.7 years 100M 10M Fiber 1M Coax 100k Data-centric 10k Network 1k (Optical) Telephone 100 Doubles every 9 months 10 Telegraph 1 Data Rate Capacity (bits/second) Capacity Rate Data 1850 1900 1950 2000 2050 Year J. Zhu, 18-200 Lecture, Fall 2004 35 Facts A single optical fiber is capable of transmiting 2x1012 bits of data per second, which is equivalent to simultaneously carry more than 30,000,000 phone conversations, or 200,000 users download (upload) information at 10 Mbits/second data rate at same time, or download all 380 CDs (each with 1 hour long music) in 1 second , or download 30 DVD movies in 1 second . Present dense wavelength division multiplexing (DWDM) technology is realizing the full potential of a single optical fiber ! A optical fiber cable may contain up to 200 fibers. J. Zhu, 18-200 Lecture, Fall 2004 36 18 Fiber-Optical Long-Haul Routes Source: KMI J. Zhu, 18-200 Lecture, Fall 2004 37 Metro Optical Network Source: Nortel Networks e.g. 10 Gbits Ethernet J. Zhu, 18-200 Lecture, Fall 2004 38 19 18-315 Introduction to Optical Communication Systems Laser Course Coverage Encoder Amp. Decoder driver laser Light Fiber receiver 9 How light carries information 9 Generation of light 9 Light traveling in a fiber 9 Amplification of Light Systems 9 Time Division Multiplexing (TDM) 9 Wavelength Division Multiplexing (WDM) 9 Optical networks Devices and Components 9 Fiber 9 LED 9 Semiconductor lasers 9 Fiber Amplifiers 9 Optical receivers 9 Optical modulators 9 Optical couplers and switches J. Zhu, 18-200 Lecture, Fall 2004 39 This course is designed to: prepare students with up-to-date education ready for the optical communication and network industry.