Ibm scientists imitate the functionality of neurons with a. What varies is the thickness of individual layers, which is determined by the. Thermal energy storage with phase change material lavinia gabriela socaciu 76 introduction thermal energy storage tes is defined as the temporary holding of thermal energy in the form of hot or cold substances for later utilization 1. Phase change memory technology phase change chalcogenides exhibit a reversible phase change phenomenon when changed from the amorphous phase to the crystalline phase. According to the size of amorphous phase and crystalline phase, the resistance of pcm in read operation is calculated. Architecting phase change memory as a scalable dram. Phasechange memory alloys have been used since the 1990s in rewritable optical disks such as compact disks cd, and later also in digital versatile disks dvd and bluray disks bd. In pcm technology, high heat over 600 c is applied to a storage cell to change the phase to store data. Braininspired computing using phasechange memory devices featured. Invited paper phasechangememory stanford university. The structure of these disks is essentially the same and is shown in fig.
There is a huge variety of different components that are available with a variety of different functions. Phase change memory is susceptible to a fundamental tradeoff of unintended vs. Abbreviated as pcm, phase change memory is a type of nonvolatile memory that is much faster than the common flash memory, and it also uses up to onehalf the power. Prams exploit the unique behaviour of chalcogenide glass. Phase change memory stanford nanoheat stanford university. In a projected memory device, the essential idea is to design the device in such a way that the physical mechanism of information storage is decoupled from the informationretrieval process18. We survey the current state of phase change memory pcm, a nonvolatile solidstate. As fabricated, the phase change material is in the crystalline, lowresistance state because the processing temperature of the beol metal interconnect layers is sufficient to crystallize the. Pcm devices as a memory device is that writes are too slow. Architectural techniques for multilevel cell phase change memory based main memory lei jiang, ph. Energy demands vary on daily, weekly and seasonal bases. We studied the temperature dependence of the resistance levels in both a projected memory.
Their ability to switch, reversibly and extremely quickly, between the crystalline and amorphous phases, combined with the high stability of both phases, makes them ideally suitable for memory applications. The chapter starts with the discovery of a one way resistance transformation phenomenon in a chalcogenide, namely molybdenite mos 2. Phase change materials exist in an amorphous and one or sometimes several crystalline phases, and. In this 4part series ron takes a look at the recentlypublished analysis by a team from ibm and yale university wiley. First flexible phasechange random access memory developed. To meet increasing performance requirements including improvements to memory speed, capacity, power usage, and. Phase composition the ni composition of the liquid phase is c l the ni composition of the solid. The electrical current passes through the phase change material between the top electrode and heater. It works by using a semiconductor alloy that can be changed rapidly between an ordered, crystalline phase having lower electrical resistance to a disordered, amorphous phase with.
Request pdf overview of phasechange chalcogenide nonvolatile memory technology phasechange nonvolatile semiconductor memory technology is. Ibm in memory computing with 1 million phase change memory. Projected phasechange memory devices nature communications. Because no electrical power is required to maintain either phase of the material, so phasechange memory is nonvolatile. Phase change memory pcm is a nonvolatile solidstate memory technology based on the large resistivity contrast between the amorphous and crystalline states in phase change materials. We survey the current state of phase change memory pcm, a nonvolatile solid state. Phase change materials have a large electrical contrast. In the older generation of pcm, heat produced by the passage of an electric current through a heating element generally made of tin was used to either quickly heat. Phase change materials and phase change memory mrs bulletin. Phase change materials are tecontaining alloys, typically lying along the getesb 2 te 3 quasibinary tie line. Nonresistancebased cellstate metric for phasechange memory. Overview of phasechange chalcogenide nonvolatile memory.
Phase change materials and phase change memory simone raoux, feng xiong, matthias wuttig, and eric pop phase change memory pcm is an emerging technology that combines the unique properties of phase change materials with the potential for novel memory devices, which can help lead to new computer architectures. Reliability enhancement of phase change memory for. We address the challenges facing this technology, including the design of pcm. Everything from passive components like resistors, capacitors and the like through devices like diodes, and onto other electronic components like transistors, fets and even. Tominaga1 phasechange memory technology relies on the electrical and optical properties of certain materials changing substantially when the atomic structure of the material is altered by heating1 or some other excitation process25. Phase change memory pcm is an emerging class of nonvolatile memory technologies that offers an attractive combination of features, making it a likely replacement for dram.
Architecting phase change memory as a scalable dram alternative. Phase amount in the double phase region the lever rule at the point b. Phase change memory pcm is a type of nonvolatile ram that stores data by changing the state of the material used, meaning it changes back and forth between amorphous and crystalline states on a microscopic level. Phasechange memory controller architecture for lowlatency. Chalcogenide phasechange materials pcms are leading candidates for such. In phasechange memory pcm, lowfield electrical resistance is typically used to quantify the programmed cell state. During writes, an access transistor injects current into the storage material and thermally induces phase change, which is detected during reads. Based on the temperature, it simulates the phase changing of pcm. This interval means that phasechange materials can be transformed from 0 to 1 by a picosecond excitation, and implies that emerging technology could store data many times faster than silicon random access memory ram for tasks that require memory and processors to work together to perform computations.
The fundamental mechanism for phasechange memory was invented in the 1960s by. Phase change materials and phase change memory eric pop. These new memory technologies exhibit a combination of characteristics that make them at least partially suitable for both main memory and storage applications. The projected memory device or cell comprises a carefully designed segment consisting of a noninsulating material projection segment that is parallel to the phasechange.
Aug 15, 2016 new discoveries about phase change memory show it can switch at picosecond scales theoretically opening the door to a dram replacement thousands of times faster than our current memory technology. For information storage, a phase change memory device uses a large contrast either in electrical resistance between the amorphous phase high. A phasechange material is one that exists in at least two phases with remarkably di. Set and reset state of pcm refers to low and highresistance state, respectively. Pcm, relying on analog current and thermal e ects, does not require control over discrete electrons. The combination of quick heating and cooling results in the amorphous phase, and this operation is referred to as a reset operation. According to its proponents, pcm technology has the potential to provide inexpensive, highspeed, highdensity, highvolume nonvolatile storage on an unprecedented scale. Extending the writeerase lifetime of phase change memory. As shown in figure 1, in the amorphous phase, the material is highly disordered there is an absence of regular order to the crystalline lattice. We have found that, if data is stored in pcm devices, the physical attributes of those devices can be exploited to achieve inplace computation. Rethinking database algorithms for phase change memory. One of the leading prototypical memories that is being investigated is phase change memory. Then the evolution of the understanding of the underlying physics governing the phase change characteristics by various investigators is.
Thermal conditions that allow for fast crystallization should not be too similar to standby conditions, e. This interval means that phasechange materials can be transformed from 0 to 1 by a picosecond excitation, and implies that emerging technology could store data many times faster than silicon random access memory ram for tasks that require memory and processors to. Designing crystallization in phasechange materials for universal memory and neuroinspired computing. This demonstration marks a significant step forward in the development of energyefficient, ultradense integrated neuromorphic technologies for applications in cognitive computing. Phasechange memory also known as pcm, pcme, pram, pcram, oum ovonic unified memory and cram or cram chalcogenide ram is a type of nonvolatile randomaccess memory. Introduction the spice model is developed for the write operation of pillarshaped phase change memory based on physics and geometry of pcm.
Phase change memory key attributes 10 5 10 6 200200 ns 30 kbs flash easy no smallbyte n. Ibm press room ibm scientists have created randomly spiking neurons using phasechange materials to store and process data. Ibm press room ibm scientists have created randomly spiking neurons using phase change materials to store and process data. University of pittsburgh, 2014 phase change memory pcm recently has emerged as a promising technology to meet the fast growing demand for large capacity main memory in modern computing systems. The storage element is a phase change memory pcm cell 1 and the selector is an ovonic threshold switch ots 2. Pcm, about 1,000 times faster than ram, is one such effort thats being extensively developed by researchers and tech giants. Breitwisch 2, michele franceschini, davide garetto, kailash gopalakrishnan 1, bryan jackson, bulen t kurdi, chung lam2, luis a. Phase change materials and phase change memory mrs. This is the first of a new lineup of memory guy posts by ron neale.
Tominaga 1 phase change memory technology relies on the electrical and optical properties of certain materials changing substantially when the atomic structure of the material is altered by heating 1 or some other excitation process 2. The phase change material is in the crystalline phase in an asfabricated device. Shenoy1 1 ibm almaden research center, 650 harry road, san jose, california 95120. Evaluating phase change memory for enterprise storage. Communications of advanced materials, volume 30, issue 9, march 1, 2018 selfhealing of a confined phase change memory device with a metallic surfactant layer, xie et al which has cast some new light. For example, a pcm cell with four distinct resistance levels can store two bits. The memory cell is built by layering a storage element and a selector. Lastras 2, alvaro padilla1, bipin rajendran, simone raoux2, and rohit s. Pcm can be built at higher chip densities than dram, which is expectedto translate into highercapacities and lower cost per gb. Phase change memory pcm recently has emerged as a promising technology to meet the fast growing demand for large capacity main memory in modern computing systems. Phase change memory pcm is an emerging technology that combines the unique properties of phase change materials with the potential for novel memory devices, which can help lead to new computer architectures. A novel scalable and stackable nonvolatile memory technology suitable for building fast and dense memory devices is discussed. This stems primarily from the fact that phase change is a thermally driven process rather than an electronic process.
An overview of phase change memory device physics to cite this article. It first calculates the heat generation of the heater, then gets the temperature of the phase. Revisiting hash table design for phase change memory. Modeling the phasechange memory material, ge2sb2te5, with a. Pcm is 500 to 1,000 times faster than normal flash memory. Current crowding at the heater to phase change material contact results in. Much ado about memory, dram and nand flash are the most common technologies currently in use for fast main memory and slower storageclass memory, respectively. Electronic components are at the core of electronics technology. The electrical and thermal properties of phase change materials are surveyed with a focus on the scalability of the materials and their impact on device design.
Phasechange memory pcm is a form of computer randomaccess memory ram that stores data by altering the state of the matter from which the device is fabricated. Because no electrical power is required to maintain either phase of the material, so phase change memory is nonvolatile. It first calculates the heat generation of the heater, then gets the temperature of the phase change material. Designing crystallization in phasechange materials for universal. Pdf on oct 1, 2016, hongsik jeong published high density pcmphase change memory technology find, read and cite all the research. Phase change memory pcm is a form of computer randomaccess memory ram that stores data by altering the state of the matter from which the device is fabricated.
Phase change memory uses a semiconductor alloy that can be changed rapidly between an ordered, crystalline phase having lower electrical resistance to a disordered, amorphous phase with much higher electrical resistance. Candidates for nonvolatile memory and neuroinspired computing devices include phasechange materials pcms, resistiveswitching oxides. This demonstration marks a significant step forward in the development of energyefficient, ultradense integrated neuromorphic technologies for applications in. Matter can exist in various phases such as solid, liquid, gas, condensate and plasma. Phase change memory joint project pcm mobile platform memory system transformation mobile ram nand pcm code storage, xip code execution, web browsing, swapping, boot, email, multitaskingram photo pictures, movies, rom in place code execution, high performance, long battery life, instant on and play, low cost single chip solution. Phasechange materials possess a unique combination of properties that make them promising candidates for the memory material in phasechange ram pcram devices. This model includes both the heater and the phase change material. This kind of memory will replace current well known flash memory. We call such a memory unit computational memory, where resistive memory devices, in particular phasechange memory pcm devices, could play an important role as building blocks. In a memory array, the pcm devices are typically placed in. Jan 29, 2016 phase change memory phase change memory also known as pcm, pcme, pram, pcram, ovonic unified memory, chalcogenide ram and cram is a type of nonvolatile randomaccess memory. Designing crystallization in phasechange materials for. Phasechange memory controller architecture for low.