Magnetoresistive RAM (MRAM) Jacob Lauzon, Ryan McLaughlin

Transcription

1 Magnetoresistive RAM (MRAM) Jacob Lauzon, Ryan McLaughlin

2 Agenda Current solutions Why MRAM? What is MRAM? History How it works Comparisons Outlook

3 Current Memory Types Memory Market primarily consists of: DRAM: High Density to Price Ratio SRAM: High Performance/Speed Flash: Non-Volatile Memory

4 Comparison of Memory Types DRAM SRAM Flash Memory Volatile Yes Yes No Speed Medium Fast Slow Power consumption High Medium Low Density Medium Low High Infinite Durability Yes Yes No Typical Use Main Memory Cache External

5 Why do we need MRAM?

6 Quest for Universal Memory Universal Memory aims to provide: High Density High Speed Non-Volatility High Durability

7 What is MRAM? Non-volatile random access memory Stores data using magnetic charge rather than electrical charge Very high speed (SRAM speed) with high density (DRAM density) Low power consumption (30% of DRAM) Key Players: Everspin(Motorola/Freescale), Canon, Crocus, Cypress, IBM, Intel, Infineon

8 MRAM Timeline 1955 Magnetic core memory developed, which influenced MRAM Writing IBM made key "giant magnetoresistive effect discoveries Adjacent ferromagnets with parallel alignment have a low resistance, while antiparallel layers produce a high resistance. IBM was able to reproduce the GMR effect with room temperature, less precise thin film structures implemented in 16.8 GB HDD Write Heads 1995 Motorola began developing MRAM

9 Single Cell/Bit Spin Valve/Magnetic Tunnel Junction (MTJ) Consists of: Free magnet, which changes polarization Thin insulation layer AKA Tunnel Barrier Fixed magnet, with permanent polarization Transistor for selecting Read Cell

10 Multiple Cells/Mem Hierarchy Individual Spin Valves/MTJs are connected in a 2D grid by bit lines perpendicular to word lines.

11 Reading Magnetic tunnel effect causes resistance to change based on the polarity of the plates Resistance can be determined by measuring the current through the cell

12 Write Methods: Toggle Decoders are used to power the appropriate bit line and word line for the write. This induces a magnetic field at the junction of the two lines which the free magnet picks up The direction of the current will determine polarization Disadvantages: High current required to induce the field Size limitation: Cells need to be spread out to avoid the the induced field overlapping into other cells

13 Write Methods: Spin Transfer Torque Uses spin-polarized current to change the polarization of the free magnet Uses much less current than Toggle method Does not induce a magnetic field so overlapping with other cells is not a problem

14 Write Methods: Others Thermal-Assisted Switching (TAS) - Uses toggle method but heats up the junction during a write to reduce the field needed Vertical-Transport (V) - Sends current through a vertical column to change the polarity. The direction of the current determines the polarity

15 Comparison to Other Memory MRAM DRAM SRAM Flash Memory Volatile No Yes Yes No Speed Fast Medium Fastest Slow Power consumption Lowest High Medium Low Density Medium High Low Highest Infinite Durability Yes Yes Yes No

16 Could MRAM be Universal Memory? SRAM vs. MRAM performance gap could be forgivable. DRAM/Flash vs. MRAM density gap is too large. Increased density -> Sufficient Increased performance -> Optimal

17 MRAM Timeline MRAM joint development started by IBM and Infineon, and Spintec created a patent with Spin Torque Transfer kbit MRAM chip was manufactured using 180 nm technology Record MRAM cell clocked at 2 GHz, Renesas Tech. Development of 65 nm STT-MRAM begins First commercial MRAM modules (4 Mbit,25$) - Freescale Toshiba continues development of 1Gb MRAM, predicting DRAM replaced by MRAM in 7 years STT-MRAM advancements announced by Crocus that compete with DRAM/Flash Samsung developed Spin Valves/Magnetic Tunnel Junctions with 17 nm technology Announcement from Buffalo to produce first SSD with MRAM Cache (Everspin STT-MRAM) Buffalo produces Industrial SSD utilizing Everspin's EMD3D064M 64Mb DDR3 STT-MRAM chip for cache

18 Future Outlook CURRENT Everspin produces EMD3D064M - 64Mb DDR3 STMRAM, scalable to 1Gb Currently MRAM cannot fully replace DRAM, SRAM, or flash MRAM can be used for small density requirement applications that require very low power consumption or cannot be accessed for long periods of time (i.e. satellites) FUTURE Potential to replace DRAM Higher density than DRAM possible, since not limited by the number of electrons in the area. Instant Startup Devices 20 Company Alliance(Micron Technology, Hitachi) - Mass production research Commercial Mass Production is targeted for 2018

19 Questions?

20 Bibliography