ELECTRONIC CIRCUITS AND APPLICATIONS
1 ROLE OF RESISTIVE MEMORY DEVICES IN BRAIN INSPIRED COMPUTING 1 2 RESISTIVE SWITCHING MEMORIES 15 3 PHASE CHANGE MEMORY 60 4 MAGNETIC AND FERROELECTRIC MEMORIES 94 5 SELECTOR DEVICES FOR EMERGING MEMORIES 132 6 MEMRISTIVE DEVICES AS COMPUTATIONAL MEMORY 162 7 MEMRISTOR BASED IN MEMORY LOGIC AND ITS APPLICATION IN IMAGE PROCESSING 170 8 HYPERDIMENSIONAL COMPUTING NANOSYSTEM IN MEMORY COMPUTING USING MONOLITHIC 3D INTEGRATION OF RRAM AND CNFET 190 9 VECTOR MULTIPLICATIONS USING MEMRISTIVE DEVICES AND APPLICATIONS THEREOF 215 10 COMPUTING WITH DEVICE DYNAMICS 249 CONTENTS 11 EXPLOITING THE STOCHASTICITY OF MEMRISTIVE DEVICES FOR COMPUTING 268 12 MEMRISTIVE DEVICES FOR DEEP LEARNING APPLICATIONS 303 13 ANALOG ACCELERATION OF DEEP LEARNING USING PHASE CHANGE MEMORY 318 14 RRAM BASED COPROCESSORS FOR DEEP LEARNING 352 15 MEMRISTIVE DEVICES FOR SPIKING NEURAL NETWORKS 385 16 NEURONAL REALIZATIONS BASED ON MEMRISTIVE DEVICES 392 17 SYNAPTIC REALIZATIONS BASED ON MEMRISTIVE DEVICES 412 18 SYSTEM LEVEL INTEGRATION IN NEUROMORPHIC COPROCESSORS 463 19 SPIKING NEURAL NETWORKS FOR INFERENCE AND LEARNING A MEMRISTOR BASED DESIGN PERSPECTIVE 482 CHAPTER 1 ROLE OF RESISTIVE MEMORY DEVICES IN BRAIN INSPIRED COMPUTING 1 1 INTRODUCTION THIS CHAPTER INTRODUCES VARIOUS TYPES OF RESISTIVE MEMORY DEVICES ALSO NAMED MEMRISTIVE DEVICES OF CURRENT INTEREST FOR BRAIN INSPIRED COMPUTING THESE MEMRISTIVE DEVICE TECHNOLOGIES INCLUDE A BROAD CLASS OF TWO OR THREE TERMINAL DEVICES WHOSE RESISTANCE CAN BE MODIFIED UPON ELECTRICAL STIMULI THE RESISTANCE CHANGES CAN LAST FOR SHORT OR LONG TIME SCALES LEADING TO A VOLATILE OR NONVOLATILE MEMORY EFFECT RESPECTIVELY MEMRISTIVE DEVICES ARE BASED ON A LARGE VARIETY OF PHYSICAL MECHANISMS SUCH AS REDOX REACTIONS AND ION MIGRATION PHASE TRANSITIONS SPIN POLARIZED TUNNELING AND FERROELECTRIC POLARIZATION THE SWITCHING GEOMETRY CAN INVOLVE A VOLUME INTERFACIAL OR CONFINED 1D FILAMENTARY REGIONS 18 ALTHOUGH THESE TECHNOLOGIES HAVE BEEN MAINLY DEVELOPED AS NONVOLATILE MEMORY DEVICES FOR STORAGE APPLICATIONS RECENTLY THEY HAVE BEEN RECEIVING INCREASING INTEREST FOR BRAIN INSPIRED COMPUTING AND MANY EXCITING DEVELOP MENTS ARE UNDERWAY IN THIS DIRECTION 1 923 TODAY WE ARE FACING A REVO LUTION DRIVEN BY THE INCREASING AMOUNT OF DATA GENERATED EACH DAY WHICH NEED TO BE STORED CLASSIFIED AND PROCESSED LEADING TO THE PARADIGM OF DATA CENTRIC COMPUTING ON THE OTHER HAND CURRENT COMPUTING SYSTEMS ARE INHER ENTLY LIMITED IN ENERGY EFFICIENCY AND DATA BANDWIDTH BY THE PHYSICALLY SEPA RATED MEMORY AND PROCESSING UNITS VON NEUMANN BOTTLENECK AS WELL AS BY THE LATENCY MISMATCH BETWEEN THE MEMORY AND PROCESSING UNITS MEMORY WALL 9 10 13 MEMRISTIVE DEVICES HAVE THE POTENTIAL TO MEET THE CONSIDER ABLE DEMAND FOR NEW DEVICES THAT ENABLE ENERGY EFFICIENT AND AREA EFFICIENT 1 INFORMATION PROCESSING THAT TRANSCENDS VON NEUMANN COMPUTING IN THE FOL LOWING SECTIONS WE DESCRIBE THE LEADING MEMRISTIVE TECHNOLOGIES AND THEIR CURRENT POTENTIAL FOR VARIOUS APPLICATIONS 1 2 TYPE OF RESISTIVE MEMORY DEVICES FIG 1 1 SHOWS A CLASSIFICATION OF THE MOST REPRESENTATIVE AND MATURE RESISTIVE SWITCHING MEMORY TECHNOLOGIES RRAM PCM MRAM AND FERAM BASED ON THEIR UNDERLYING PHYSICAL MECHANISM LOCATION OF THE SWITCHING REGION AND THEIR CURRENTVOLTAGE OR RESISTANCEVOLTAGE BEHAVIOR FIGURE 1 1 A SKETCH OF RESISTIVE RANDOM ACCESS MEMORY RRAM DEVICES FEATURING FILA MENTARY TOP AND INTERFACIAL SWITCHING BOTTOM THE CORRESPONDING REPRESENTATIVE CURRENTVOL TAGE CHARACTERISTICS ARE REPORTED ON THE RIGHT INDICATING BIPOLAR SWITCHING FROM A HIGH TO LOW RESISTANCE STATE SET AND VICE VERSA RESET FOR FILAMENTARY SYSTEMS AN INITIAL HIGH VOLTAGE FORM ING IS REQUIRED B TOP SCHEMATIC DRAWING OF PHASE CHANGE MEMORY PCM CELL IN THE CRYSTAL LINE LRS AND AMORPHOUS STATE HRS OF THE CHALCOGENIDE MATERIAL BOTTOM CURRENTVOLTAGE AND RESISTANCE PROGRAMMING POWER CHARACTERISTICS C FERROELECTRIC RANDOM ACCESS MEMORY FERAM AND ITS POLARIZATIONELECTRIC FIELD HYSTERESIS LEFT AND FERROELECTRIC FIELD EFFECT TRANSIS TOR FEFET WITH CORRESPONDING DRAIN CURRENT VERSUS GATE VOLTAGE CHARACTERISTICS RIGHT D SKETCH OF A MAGNETIC TUNNEL JUNCTION MTJ TOP AND EVOLUTION OF THE RESISTANCE VERSUS APPLIED VOLTAGE BOTTOM FOR THE PARALLEL AND ANTIPARALLEL CONFIGURATIONS OF THE MAGNETIZATION ORIENTATION OF THE PINNED AND FREE LAYERS THE MTJ IS THE KEY ELEMENT FOR A MAGNETIC RANDOM ACCESS MEM ORY MRAM ELECTRONIC CIRCUITS AND APPLICATIONS 2 RESISTIVE RANDOM ACCESS MEMORY RRAM SHOWN IN FIG 1 1A IS BASED ON A TWO TERMINAL STRUCTURE WHERE A SWITCHING MEDIUM IS SANDWICHED AMONG TWO ELECTRODES WHOSE RESISTANCE CAN BE SWITCHED REVERSIBLY AMONG TWO OR MORE STATES BY APPLYING EXTERNAL ELECTRICAL STIMULI 13 2428 MANY MATE RIALS CAN BE USED FOR THE SWITCHING MEDIUM INCLUDING INORGANIC AND ORGANICS ONES TRANSITION METAL OXIDES PEROVSKITES CHALCOGENIDES POLYMERS ETC AND THE RESISTIVE SWITCHING PROCESS TYPICALLY INVOLVES THE CREATION AND RUP TURE OF CONDUCTIVE FILAMENTS CF SHORTING THE TWO ELECTRODES THESE TYPES OF DEVICES ARE ALSO NAMED FILAMENTARY RRAMS THE LOW RESISTANCE STATE LRS OCCURS WHEN A CF BRIDGES THE TWO METAL LAYERS FIG 1 1A TOP WHILE THE HIGH RESISTANCE STATE HRS IS ACHIEVED BY PARTIAL DISSOLUTION OF THE FILAMENT THE DEVICES BASED ON OXYGEN ION MIGRATION EFFECTS AND SUBSEQUENT VALENCE CHANGE OF THE METALS IN METAL OXIDES ARE NAMED VALENCE CHANGE MEMORY VCM OR ANION BASED MEMORY AND THE RESULTING CF IS FORMED BY A LOCAL IZED CONCENTRATION OF DEFECTS EXAMPLES OF VCM RRAM ARE RELATED TO MATE RIAL SYSTEMS BASED ON HFOX TAOX TIOX SIOX WOX AL2O3 OR OTHER TRANSITION METAL OXIDES IN COMBINATION WITH TIN TAN TI TA AND PT ELECTRO DES 3 14 26 28 THERE IS ANOTHER CLASS OF DEVICES WHERE THE CF IS FORMED BY THE METAL ION MOVEMENT FROM THE ACTIVE ELECTRODE OFTEN AG OR CU INTO THE SWITCHING MEDIUM WHICH ARE NAMED AS ELECTROCHEMICAL METALLIZATION MEMORY ECM CATION BASED MEMORY OR EVEN CONDUCTIVE BRIDGE RANDOM ACCESS MEMORIES CBRAM 4 14 26 27 THESE TYPES OF RRAMS ARE FABRI CATED BY USING AN ACTIVE ELECTRODE AG CU CO ETC IN COMBINATION WITH AN INERT ELECTRODE TAN W PT ETC WHILE THE SWITCHING MEDIUM IS BASED ON SOLID ELECTROLYTES SUCH AS GESE GES AGXS CUXS OR EVEN OXIDES SUCH AS SIO2 FOR FILAMENTARY RRAMS VCM OR CBRAM AN INITIAL ELECTROFORMING STEP IS NECESSARY TO ESTABLISH THE FIRST FILAMENT FORMATION AFTER THAT FORMING STEP THE CELL CAN BE REPEATEDLY SWITCHED BETWEEN THE LRS AND HRS CYCLING ENDURANCE UP TO 1041012 CYCLES DEPENDING ON THE MATERIALS SYSTEMS AND IF THE MEASUREMENTS ARE DONE AT A SINGLE DEVICE OR ARRAY LEVEL RRAM IS CON SIDERED A NONVOLATILE MEMORY SINCE THE TWO STATES CAN BE RETAINED FOR A LONG TIME RETENTION UP TO MANY YEARS INCIDENTALLY IT IS WORTH NOTING THAT SIMILAR DEVICE STRUCTURES ESPECIALLY ECM CAN BE FURTHER ENGINEERED TO ACHIEVE A THRESHOLD SWITCHING BEHAVIOR SUITABLE FOR SELECTOR APPLICATION MORE DETAILS IN CHAPTER 5 RRAM BASED COPROCESSORS FOR DEEP LEARNING OR EVEN SHORT TERM RETENTION TO BE EXPLOITED IN SPIKING NEURAL NETWORKS SNNS CHAPTER 17 SYNAPTIC REALIZATIONS BASED ON MEMRISTIVE DEVICES AN ADDITIONAL CLASS OF RRAM RELIES ON UNIFORM INTERFACIAL SWITCHING FIG 1 1A BOTTOM IN WHICH THE CONDUCTANCE SCALES WITH THE JUNCTION AREA OF THE DEVICE AND THE MECHA NISM IS RELATED TO A HOMOGENOUS OXYGEN ION MOVEMENT THROUGH THE OXIDES LEADING TO THE MODULATION OF THE ELECTRODE OXIDE INTERFACIAL SCHOTTKY BARRIER 2 2326 THIS RRAM TYPE EXHIBITS AN ANALOG SWITCHING NATURE AND THE INITIAL ELECTROFORMING IS NOT NECESSARY THIS UNIFORM SWITCHING IS OFTEN REPORTED IN COMPLEX OXIDES AND PEROVSKITE SUCH AS BISMUTH FERRITE ELECTRONIC CIRCUITS AND APPLICATIONS 3