CMU solution is most complex of three-must control individual heights of 6,400 probe tips,required by recording technology
MEMS BASED INTEGRATED CIRCUITMASS STORAGE SYSTEMS Presented by prashant singh (imi2011003)
HighlightsNew secondary storage technology that could revolutionize computer architecture. -Faster than hard drives -Lower entry cost -Lower weight and volume -Lower power consumptionDiscuss physical description of device.
Disk Drive limitationsDisk-drive capacities double every 18 months -better 60% per year growth rate of semiconductor memoriesTwo major limitations of disk drives are….. -Access times decreases have been minimal -Minimum entry cost remains too high for many applications
Problem SpecificationRequirement of mass storage system that can break both barrier -Access times -Minimum entry costNew mass storage should also be significantly cheaper than non-volatile RAM -$100 now buys 1 GB of flash memory
MEMSMEMS use -Same parallel wafer-fabrication process as semiconductor memories -Keeps the prices low -Same mechanical positioning of R/W heads as disk drives -Data can be stored using higher density thin film technology
Main Advantages Of MEMS Potential for dramatic decrease in -Entry cost(10x cheaper than RAM) -Access time -Volume -Mass -Power dissipation -Failure rate -Shock sensitivity Integrate storage with computation -Complete system-on-chip integration -Processing unit -RAM -Non-volatile storage
MEMS storage prototypeLike a disk drive, it has -recording heads -a moving magnetic recording mediumMajor departures from disk drive architecture are -MEMS recording heads-probe tips-are fabricated in a parallel wafer level manufacturing process -Media surface does not rotate(Data latency decreases)
Media Surface MovementMedia surface that rotate requires ball bearingsVery small ball bearing may have “striction” problem that prevent accurate positioning -Element would move by sticking and slippingBest solution is to have media sled moving in X-Y directions -Sled moves in Y-direction for data access -Sled is suspended by spring
Conceptual View of “Moving Media”(CMU prototype) Read/Write Read/writeActuators tips tips Springs Magnetic Media Bits stored Media underneath side view each tip
The Media SledActuator pull sled in both dimensionsSize 8mm X 8mm X 500µmHeld over the probe tip array by a network of springsMotion applied through electrostatic actuators -Motion limited to 10% or less of suspension/actuator length -Each probe tip can sweep 1% of the media sledInclude large number of probe tips for -Improving data throughput -Increasing system reliability Read write operation
Probe Tip Positioning Most MEMS include some form of tip height control because -Media surface is not perfectly flat -Probe tip height may varyCMU(Carnegie Mellon University,Pennsylvania,US) prototype places each probe tip on a separate cantilever -Cantilever is electrostatically actuated to a fixed distance from the media surfaceIBM Millipede -Uses 32 x 32 array of probe tips -Each tip is placed at the end of a flexible cantilever -Cantilever bends when tip touches surfaceHP design places media surface and probe tips sufficiently apart IBM Millipede -No need to control probe tips height
Probe Tip FabricationMajor challenge is fabricating read/write probe tips in a way that is compatible with the underlying CMOS circuitryThis includes -thermal compatibility -geometrical compatibility -chemical compatibility……..
Failure ManagementMEMS devices will have internal failures -Tips will break during fabrication/assembly, use -Media can wear(erosion/sideways displacement)
Storing, Reading and Writing BitsCMU prototype uses same magnetic recording technology as current disk drives -Minimum mark size around 80µm x 80µmOther solutions include -Melting pits in a polymer (IBM Millipede) -Raises tip wear issues
Potential ApplicationLighter and less shock sensitive than disk drives -Great for notebook PC’s,PDA’s and video camcordersLower cost than disk drives in 1 to 10 GB range -Will open many new applicationsHigh areal densities -Great for storing huge amounts of dataCan combine computing and storage on a single chip E.g. Average service time around 0.52 ms -Disk drive service time is 10.1 ms -Key factor for service time is X-seek time