Transcript for:
Ferroelectric Random Access Memory (FRAM)

hello everyone I am Bishnu Bantu the city Putin and I'm going to talk about ferroelectric random access memory in this presentation these are the topics I will be covered in stool in this presentation ferroelectric Ram is nothing but a random access memory which has a ferroelectric capacitor in it so cute and it's hysteresis to achieve normal eyetality it is also widely known as Ephraim or Ephraim this Ephraim is very similar to theorem in construction and in functionality it is similar to flash ROM let me talk a bit about ephram's history ephram's but initially proposed by MIT graduate Dudley Alan Buck as a part of his master's thesis back in 1952 much of Ephron technology was developed by Ram from a fabless semiconductor company and put it sue put it sue has a very large production line for ephraim using this line which it so has been producing stand-alone Ephraim's and specialized ships with embedded FM's rammed Ron and Fujitsu have been working together until 2001 later on Ram chrome collaborated with Texas Instruments and IBM to develop Ephrem test chips in a 180 nanometer process many research projects were also done during this pleaded structure of ephraim this is the basic structure of a nephron it is very much similar to D Ram although it contains a ferroelectric material instead of a dielectric material as shown in the figure Efrain conscious of a word line of bit-line transistor and a ferroelectric capacitor to perform various operations like read write and store as i told previously ephram's use ferroelectric material instead of dielectric material to let me tell you a bit about ferroelectric materials they have a crystalline structure with an atom at the center this atom has two equal and low energy states based on the position of the atom compounds which exhibit this behavior are Christ as kirovsk it barium titanate and let zucchini titanate exhibit this behavior when an electric field is applied to the atom the atom moves in the direction of the applied field this property of the atom to move determines the state of the material and can also be used to stay data a polarization state and down polarization states are the two states defined because there is an energy required within the transistors there is a hysteresis loop over which the ferroelectric material operates it should be noted that the ferroelectric crystals do not contain any ferrous material they gain their name from the similarity of the curve of charge parted as a function of voltage to the familiar pH curve of a magnetic material in fact ferroelectric materials are switched only by electric fields and they are not affected by magnetic fields circles with arrows represent the polarization state of the material at the indicated fields the actual loop is measured in the one-one-one orientation the two states in a ferroelectric material can be used in a capacitor to create two states for a memory cell the key to the operation of the Ephrem is that the capacitance of a ferroelectric capacitor is variable if the capacitor is not switched but an electric field is applied that is when no change in polarization then it behaves in the normal linear fashion however if it is switched then an additional charge is induced and this must have resulted from with increase in capacitance to MA enable this effect an active element FET is used to enable the individual cell access a word line a bit line is used in enough RAM memory cell Ephraim read cycle the read operation of a nephron memory requires a number of stages it is very similar to that used within dynamic Ram deira the bit line voltage is simply compared to a reference this reference is set between two Elevens letters about the untwist and below the switch voltages the sense amplifier then acts as a comparable amplifying the difference to give a the logic one or logic 0 to look at the sequence for closely the cell will initially be in its inactive state at the bit line is low and the word line is low as shown in Figure a it then processes through the memory access sequence the access operation starts by placing voltages onto the word line as defined in B there are two cases that need to be considered by placing a world base across the capacitor fillet the switch or not switch dependent upon its state when capacitor state switches these voltages place a field across a ferroelectric capacitor it switches as shown and see this switching process induces a change which is shared with with line capacitance represented by C width and the switched ferroelectric capacitor CS there is also a small capacitance resulting from the transistor and other interconnection parasitics but the effect is generally small the resulting voltage on the bit line is therefore proportional to the ratio of capacitances hence the voltage on the bit line is CS divided by the product of C bit and BD D when there is no switching of capacitor state then there is no additional charge induced it can be seen that the data within the cell can be changed in the read operation that is reading in F lamp is a destructive process if therefore requires the cell to be rewritten if it was changed the f-m memory operation is designed so that the charge induced in the switched capacitor is at least twice a charge available from the unstretched capacitor this means that the switched capacitance must be at least twice the unstretched capacitance if then follows the bit line voltage but the switched case will be at least twice that of the unstretched phase this voltage can be sensed using sense amplifiers similar to those used in dr amps also like diagrams FM's have a cycle time this means that the time between the successive blind of accesses is equal to the time and not just the access time right operation the ephram's operation for writing to memory addresses using the same principles as those employed in the read operation the control circuitry for the memory applies a field in the required direction across the ferroelectric capacitor to write the desired data once in place the data will remain intact even when the power is removed from the chip as it requires energy to switch the memory from one state to another charge does not leak away as in other types of memory including DRAM or even flash to a small degree and will remain intact indefinitely when compared to other memories FM is as fast as SRAM's with very low power consumption but it takes more area and this is fairly costly FM is very useful as it is non-volatile that is it retains information even when power is lost access times are the same as forest ramps f ramps consume very less power and thus operate at a very low voltage with high light engines which makes it superior over others speaking of drawbacks f ramps have very low densities resulting in more real estate they are very costly which limits their manufacturing capabilities f ramps have wide applications they are being used in automotive shift by wire and navigation control in computing such as SSDs and network routers in advanced metering gaming and POS systems in motion control and process controls and also in virus memory finally to conclude Ephraim has many advantages compared to other memories with a few compromises needed overall performance of Ephraim can be improved by improving its storage density using stacking and 3d information improving manufacturing process because conventional process degrades ferroelectric Lehrer and also by reducing its size these are the references I used which will give you more information on F x and it's working hope this presentation was useful thank you