1. VLSI FUTURE and SPINTRONICS

2. Questions...  What is spintronics ?  How we came to know about it ?  Why we need it ?  How we can use this technology to do the needful ?

3. What is spintronics ?  Spintronics (meaning "spin transport electronics"), also known as magneto- electronics, is an emerging technology which exploits the intrinsic spin of electrons and its associated mag. moment, in addition to its fundamental electronic charge, in solid-state devices.

4. How we came to know about it ?  In quantum mechanics, the spin angular momentum of any system is quantized: its magnitude can only take values |S| = h/2π [ s (s+1) ] 1/2. where h = planck’s constant s = spin quantum no is a non-negative integer or half-integer (0, 1/2, 1, 3/2, 2, etc.) value of s depends only on the type of particle, and cannot be altered in any known way (in contrast to the spin direction).For electron s= ½ & considering spin direction, s = ±1/2 for an electron

5.  Spin magnetic moment for a particle with charge q, mass m, and spin S can be found by calculating: (µ s ) vector = g (q/2m) (S) vector

6. STERN - GERLACH EXPERIMENT  Suppose we fire a beam of electrons through a magnet

7.  Suppose the electron has a magnetic moment µ s  Then the interaction of the field with the electron is - µ s.B  The z-component of the force on the electron is F z = d/dz (- µ s.B)

8.  Depending on polarity of µ s and thus spin orientation force with will be upward or downward. if µ s < 0 direction of force will be downward µ s > 0 direction of force will be upward

9. Beam separation & filtering

10.  Beam splitting  Path of a “spin up” electron

11.  Path of a “spin down” electron  For a beam of electrons, one-half will go follow the upper path while and other half will follow the lower path

12. Spin Filter

13. Why are we doing this ?  In 1965 Gordon Moore,Intel co-founder gave a statement which is today known as Moore's Law.  Moore’s law states that the number of transistors on a chip will double about every two years.

14. MOORE’s ORIGINAL GRAPH

16. Revolution will take us to..  The world's first 2-billion transistor microprocessor delivered in next-generation Intel® Itanium® processors codenamed Tukwila  Intel has demonstrated its 32nm logic process with a functional SRAM packing more than 1.9 billion gate transistors. It's a monumental step towards delivering 32nm microprocessors in 2009

17. D e n s e r a n d D e n s e r..... ? ? ?  And what are these 1.9 billion transistors? They're the tiny switches that process the ones and zeroes that make up our digital world. They enable Intel to continue to deliver record- breaking PC, laptop and server processor speeds. And they're all packed onto a single memory cell nearly half the size of the 45nm cell—which means, for example, that Intel will be able to deliver more cores on the same die and more cache for even greater performance in the future.

18. VLSI DESIGN CONFERENCE’09  Actel Corp. displayed its whole array of FPGAs ranging from Pro ASIC3, a flash-based low-cost FPGA family; Igloo, a 5W low-power and high-density FPGA family; Fusion, a mixed-signal FPGA family; RTAX-S, a radiation-tolerant family for space applications; and Core MP7, a low-cost 32bit microprocessor core.

19. Dirk meyer’s words...  In his keynote speech, Dirk Meyer, president and chief operating officer of Advanced Micro Devices Inc., said, "Profitability in the semiconductor industry is beginning to show signs of decline. Customers are beginning to demand more than just performance—power efficiency is now the foremost demand. The industry needs to recognise this trend and make customer-centricity the driver and energy- efficiency the cornerstone of its offerings."

20. SEMICONDUCTOR MANUFACTURING  10 µm 90 nm 10 µm 90 nm  3 µm 65nm 3 µm 65nm  1.5 µm 45 nm 1.5 µm  1 µm 32 nm (Double Patterning) 1 µm32 nm (Double Patterning)  800 nm 22 nm (End of Planar Bulk CMOS) 800 nm22 nm (End of Planar Bulk CMOS)  600 nm 16 nm (Transition to Nanoelectronics) 600 nm16 nm (Transition to Nanoelectronics)  350 nm 11 nm (Nanoelectronics) 350 nm11 nm (Nanoelectronics)  250 nm 250 nm  180 nm 180 nm  130 nm 130 nm

21. What after 11 nm ?????  Reported estimates indicate that transistors at these dimensions are significantly affected by quantum tunneling. As a result, non- silicon extensions of CMOS, using nanotubes/ nanowires, as well as non-CMOS platforms, including molecular electronics, spin-based computing, and single-electron devices, have been proposed. Hence, this node marks the practical beginning of nanoelectronics.

22. QUANTUM TUNNELLING  Quantum Mechanics says that every thing in this world is a particle as well as a wave.  According to DE BROGLIE’s HYPOTHESIS of DUAL NATURE OF MATTER & RADIATION, all particles behave as a particle and a wave though wave properties are prominent for microscopic particles and particles properties are prominent for macroscopic particles.

23.  Even if E(particle energy) < V(barrier potential) then Quantum Mechanics says that there is a remote yet considerable chance of finding the particle on the other side of the barrier. The process used to explain this crossing of the barrier phenomenon is called Tunneling. Tunneling is a process by which the particle wave tunnels through (or makes it way through) the potential barrier to the other side and the probability term that describes this event is called the Tunneling Coefficient.

24.  Tunneling Coefficient = P = e (-2KL)  Where,  L = width of the Potential Barrier.  K = [(2m ( V – E )]/h = wave number and h is the Planck’s constant  P defines the probability of a particle of energy E to undergo Tunneling across a barrier of width L and height V.

26. MIGRATION...  As the size of the transistor approaches the dimension of atoms. Well before this limit there will already be severe problems with leakage and heat dissipation.  This is one of the reasons, in addition to the relevance for fundamental physics, why scientists have been eager to find alternate manufacturing processes.

27. SPINTRONICS

29.  Conventional electronic devices ignore the spin property and rely strictly on the transport of the electrical charge of electrons  Adding the spin degree of freedom provides new effects, new capabilities and new functionalities  Spin does not replace charge current just provide extra control  Information is stored into spin as one of two possible orientations

30. ADVANTAGES...  Spintronic devices offer the possibility of enhanced functionality, higher speed and reduced power consumption  Spin lifetime is relatively long, on the order of nanoseconds whereas charge can be destroyed by interaction with impurities or other charges  Spin currents can be manipulated by applying magnetic fields(precession)

31.  Spin devices may combine logic and storage functionality eliminating the need for separate components  Magnetic storage is nonvolatile  Binary spin polarization offers the possibility of applications as qubits in quantum computers

32. Giant Magneto Resistance  The GMR sandwich structure consists of alternating ferromagnetic and non-magnetic (paramagnetic or normal-metal) metal multilayers.  When the magnetization of the two outside layers is aligned, lowest resistance

33.  Conversely when magnetization vectors are anti-parallel, high Resistance.  Small fields can produce big effects.  Parallel and perpendicular current.

34. Parallel Current GMR  Current runs parallel between the ferromagnetic layers  Most commonly used in magnetic read heads  Has shown 200% resistance difference between zero point and antiparallel states

35. Spin Valve  Simplest and most successful spintronic device  Used in HDD to read information in the form of small magnetic fields above the disk surface

37. Perpendicular Current GMR  Easier to understand theoretically, think of one FM layer as spin polarizer and other as detector  Has shown 70% resistance difference between zero point and antiparallel states  Basis for Tunneling Magneto-Resistance

38. Tunnel Magnetoresistance  Tunnel Magnetoresistive effect combines the two spin channels in the ferromagnetic materials and the quantum tunnel effect  TMR junctions have resistance ratio of about 70%  CoFeB/MgO/CoFeB barrier junctions have produced 230% MR. Fe/MgO/Fe barrier junctions have produced 200% MR

40. MRAM – Birth of Super memory  MRAM uses magnetic storage elements instead of electric used in conventional RAM  Tunnel junctions are used to read the information stored in Magnetoresistive Random Access Memory(MRAM), typically a”0” for zero point magnetization state and “1” for antiparallel state

42.  Attempts were made to control bit writing by using relatively large currents to produce fields  This proves unpractical at nanoscale level because large currents may damage it

43. SPIN TRANSFER  Current passed through a magnetic field becomes spin polarized  Spin polarized current passing into a nanoscale magnet tends to deposit some of its spin angular momentum into the magnet, thereby applying a large torque to the magnetization within the external magnet

44.  In the hard disk industry, where a series of nanoscale magnetic layers called a spin valve is often used to measure the small local magnetic fields above the disk surface, this is an undesirable effect, as it hinders the ability to measure the state of the valve without disturbing it. In the MRAM industry, however, this effect may prove incredibly useful in reducing power consumption.spin valveMRAM

45.  The spin transfer mechanism can be used to write to the magnetic memory cells  Currents are about the same as read currents, requiring much less energy

46.  MRAM promises:  Density of DRAM - DRAM stores one bit in only one capacitor and transistor, very dense but very power hungry because capacitor loses charge, must be frequently refreshed  Speed of SRAM - SRAM stores one bit in six transistors, faster than DRAM but less dense  Non-volatility like flash

47.  Therefore, MRAM retains data after a power supply is cut off, potentially eliminating that seemingly endless boot time of conventional computers when data from the hard drive is transferred to RAM, (imagine your PC starting as your Television, ), as well as loss of data when the computer is suddenly shut off.  MRAM has much faster write speeds(current speed of the MR2A16A device is 57 MB/s and an address access time of about 15 nanoseconds) than Flash and has an unlimited endurance, meaning that MRAM is not subject to the degradation suffered by Flash.

48. MRAM – Reading & Writing  To READ a bit of information, a current is passed through the memory cell. If the magnetic moments are in a parallel orientation, then the detected resistance would be smaller than if they were in an anti- parallel orientation.

50.  WRITE is achieved by the alignment of the magnetic moments of the two memory layers into one or the other relative orientation. Current is passed through two sets of parallel wires or write lines (called a bit line and a digit or word line), which pass over and beneath the memory cells, perpendicularly and at their intersections lie the magnetic memory cells, each defined by one particular bit line and one particular digit line. To write to a particular memory cell (bit), current is passed through the two wires that intersect at that memory cell. The magnetic field that is generated from current passing through a wire can change the orientation of the magnetic moments of the particular memory cell.

52. Comparision...

53. SPIN TRANSISTOR  Ideal use of MRAM would utilize control of the spin channels of the current  Spin transistors would allow control of the spin current in the same manner that conventional transistors can switch charge currents  Using arrays of these spin transistors, MRAM will combine storage, detection, logic and communication capabilities on a single chip  This will remove the distinction between working memory and storage, combining functionality of many devices into one

54. DATTA DAS SPIN TRANSISTOR  The Datta Das Spin Transistor was first spin device proposed for metal-oxide geometry, 1989  Emitter and collector are ferromagnetic with parallel magnetizations  The gate provides magnetic field  Current is modulated by the degree of precession in electron spin

56. CONCLUSION Interest in spintronics arises, in part, from the looming problem of exhausting the fundamental physical limits of conventional electronics. However, complete reconstruction of industry is unlikely and spintronics is a “variation” of current technology The spin of the electron has attracted renewed interest because it promises a wide variety of new devices that combine logic, storage and sensor applications.

57. Moreover, these "spintronic" devices might lead to quantum computers and quantum communication based on electronic solid- state devices, thus changing the perspective of information technology in the 21st century.

58. Thankyou T H A N K Y O U