Mike Cassel Institut für Datentechnik und Kommuni- kationsnetze, TU Braunschweig D-38023 Braunschweig Tel. ++49-0531-391-3741 Fax ++49-0531-391-4587 E-mail: [email protected]
The Impact of Non-Volatile Erich Weih Astrium GmbH Semiconductor Memory Devices on D-88039 Friedrichshafen Tel. ++49-7545-8-9069 Future Spaceborne Mass Memories Fax ++49-7545-8-5626 E-mail: [email protected] Non-Volatile Semiconductor Memory Devices
on Future Spaceborne Mass Memories 2
Overview
o Introduction – The Ideal Memory Device o Non-Volatile Memory Technologies – Floating-Gate Memory – Ferroelectric Memory – Magnetoresistive Memory o Example Flash Memory Unit (FMU) – Design Drivers – Flash Memory Particularities – Architectural Overview o Conclusion
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
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The Ideal Memory Device
o Fast access o Random access o High integration density o Low power dissipation o Non-volatile o No wear-out o Multiple source
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
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Floating-Gate Memory – Storage Effect
o EPROM, EEPROM and Flash-Memory exploit same storage effect o Floating gate embedded in gate insulator of MOS transistor is charged or discharged
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
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Floating-Gate Memory – Today’s Properties
o EEPROM, write by Fowler-Nordheim tunneling – Random slow write access (40µs), moderate read access (70ns) – Device capacity 4 Mbit (Atmel) o Nor-Flash, write by hot electron injection, bulk erase – Random moderate speed, read/write access (100ns) – Device capacity 64 Mbit (Intel, AMD) o Nand-Flash, write by Fowler-Nordheim tunneling, bulk erase, block access – Random slow speed read/write access to blocks (10µs/200µs) – Random high speed read/write access within block bounds (50ns) – Device capacity 1 Gbit (Samsung, Toshiba, Hitachi) o Disadvantages to volatile devices (SRAM, DRAM) – No fast random access – Limited endurance (1E6 write/erase cycles)
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
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Ferroelectric RAM (FeRAM) - Storage Effect
o Ferroelectric material has two stable polarization states which can be altered by applying voltage o Ferroelectric material is used as a capacitor in a non-volatile DRAM o Potential: fast random access, improved endurance compared to floating gate o Ferroelectric material has two stable polarization states which can be altered by applying voltage o Cell size can be significantly smaller compared to DRAM cell o Destructive read decreases endurance (1E10 read/write cycles)
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
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Ferroelectric RAM (FeRAM) – Today’s Properties
o Moderate speed (70ns random access read/write) o 1 Mbit prototypes (Fujitsu) o 128 kbit radiation hardened (1E6 rad, Celis)
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
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Magnetoresistive RAM (MRAM) - Storage Effect
o Based on magnetic tunnel junction (MTJ) o Potential: Very fast random access, unlimited endurance o Non-destructive read o Cell size can be significantly smaller compared to DRAM cell, even smaller than FeRAM o High radiation tolerance expected o Could replace all existing memory technologies
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
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Magnetoresistive RAM (MRAM) – Today’s Properties
o High speed (15ns random access read/write) o Very high endurance (>1012 store/recall) o 1 Mbit prototypes (Honeywell)
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
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Example Flash Memory Unit (FMU) - Design Drivers
o Aggregate data rate of 350 Mbps via 7 interfaces o Module capacity of 64 GByte o Low volume and mass with state-of-the-art components and without usage of expensive miniaturization o Low power consumption o Main control and peripheral functions in reconfigurable FPGA
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
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Example Flash Memory Unit (FMU) - Flash Memory Particularities
o 1 Gbit Nand-Flash memory devices, characterized by 512 Byte data buffer per device with 50ns cycle time (read/write), transfer of data buffer to Flash device array needs 500µs max. Þ write data rate appr. 7 Mbps per device o Quasi-parallel write to 64 devices (1 wordgroup) achieves required data rate o Memory array is organized in 16 rows with simultaneous access to 4 byte-wide devices (32 bit data bus) o Bit error failure mechanism requires Hamming error correction in 4 independent channels, error correction uses spare area of 16 Byte in each Flash device
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
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Example Flash Memory Unit (FMU) - Flash Memory Particularities
o Memory Wordgroup Organization
slot # 0 1 2 3 14 15
8
8 ... 8
8
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
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Example Flash Memory Unit (FMU) - Architecture
o Flash memory cell wear-out effect demands real-time address mapping Flash memory array bad block table stored in EEPROM, address generation and real-time mapping individually for each interface in FPGA o Reconfigurable FPGA with configuration EEPROM programmed via 32 bit command bus o Data block size 32 kByte (64 ICs x 512 Byte) buffered in DPRAM to multiplex data interfaces o 512 devices needed to achieve required capacity Þ stacking of memory devices (8 high) o Weight 880 g including frame o Primary power consumption 10,7 W at 350 Mbps read/write
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
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< 350 Mbps opt. 410 Mbps
optional I/F 8 8 8 Write I/F Adapter 8 8 I/F 8 Write I/F 0 32 DP 32 Error 32 Adapter RAM 8 Correction 8 I/F 8 Write I/F 1 Adapter 8 8 I/F 8 Write I/F 2 Adapter Data I/F Formatter Write I/F 3a 8 x (16 x 4) Adapter 8 128 M 8 I/F Address Address (or 256 M 8) Write I/F 3b Adapter Generator Mapping Flash Memory I/F 8 Array Read I/F 0 Adapter I/F 8 Read I/F 1 Adapter
Fast Module8 CMD I/F 32 CMD 32 Timing & I/F Control Control
3.3 V DC/DC 28 V XILINX-FPGA Converter Configuration 2.5 V EEPROM
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
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Conclusion
o Today‘s non-volatile Flash devices are a strong candidate to replace DRAMs in many mass memory applications o Low block access speed of Flash memory enforces operation of many devices in parallel o Future semiconductor memory devices (FeRAM, MRAM) promise very high access speed combined with non-volatility and call for studies on their applicability for space electronics
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
on Future Spaceborne Mass Memories 16
Floating-Gate Memory – Storage Effect
o Flash-Memory uses channel hot electron injection for programming and Fowler-Nordheim tunneling for erasing o EEPROM uses Fowler-Nordheim tunneling for both functions
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
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Floating-Gate Memory – Flash Memory
o Flash Memory divided in Nor-Type and Nand-Type
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium Non-Volatile Semiconductor Memory Devices
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Ferroelectric RAM (FeRAM) - Hysteresis
M. Cassel, IDA; E. Weih, Astrium September 19, 2001 © IDA, Astrium