UNDERSTANDING THE LIMITS OF SEMICONDUCTOR TECHNOLOGY

Transcription

1 UNDERSTANDING THE LIMITS OF SEMICONDUCTOR TECHNOLOGY Department of Electronic Engineering UPC, Barcelona, Spain OUTLINE OF THE COURSE Introduction and motivation Limits of the technology at fundamental, material and component level Limits of the technology due to the manufacturing process Limits of the interconnections and analogue roadmap Semiconductor technology alternatives

2 Causes of limitation in semiconductor technology Fundamental laws Circuit level Noise and interconnections Materials Manufacturing Manufacturing defects MOS device Economical Process fluctuations Causes of limitation in semiconductor technology Fundamental laws Circuit level Noise and interconnections Analog and RF circuits Materials Manufacturing Manufacturing defects Test Technology MOS device Economical Process fluctuations 2

3 Moore s law : the number of integrable devices in a single Semiconductor crystal duplicates each 8 months Evolution Evolución of the complexity de la complejidad of CIs de (Moore s los CI's Law) Año (Mbits) Evolucion Evolucion of the memorias capacity of DRAM DRAMs , 0, Photolithography Dimension critical critica dimension (λ) (λ) 2 (micras),5 0, Intel 486 Semiconductors materials () Unitary Si, Ge (2) Compound (a) IV-IV Si-Ge (b) III-V Al-P, Al-As, Al-Sb Ga-P, In-P, In-As (c) II-VI Zn-O, Zn-S, Zn-Se Zn-Te, Cd-S, Cd-Se d) IV-VI Pb-S, Pb-Se, Pb-Te (3) Alloys (a) Ternary Al x Ga -x As Cd -x Mn x Te Ga As -x P x (b) Quaternary Al x Ga -x As y Sb -y Ga x In -x As -y P y II III IV V VI 4 Be 2 Mg 3 Al 5 B 6 C 7 N 8 O 4 Si 5 P 6 S 30 Zn 3 Ga 32 Ge 33 As 3 4 Se 48 Cd 49 In 50 Sn 5 Sb 52 Te 80 Hg 8 Tl 82 Pb 83 Bi 84 Po Brief periodic table 3

4 Crystalline structure Semiconductor Estructure Reticular constant (Å) (a) Si diamant 5,43095 Ge diamant 5,6463 Ga-As zinc-blend 5,65330 Pb-S rock-salt 5,93620 (300 K) Å = 0-8 cm Bloch theorem If U(x) is periodic: U(x+a) = U (x) Ψ (x+a) = e ika Ψ (x) Idealization of Kronig-Penney R. F. Pierret and G. W. Neudeck, Modular Series on Solid State Device, vol. VI, Advanced Semiconductor Fundamentals, Addison-Wesley, 989 4

5 Energy bands in a crystal Ec Eg Ev Forbidden band material Eg (ev) Ge 0.66 Si.2 Ga-As C N and P type crystals (extrinsec semiconductors) N type P type N type P type 5

6 Distribution of electron energies and carriers concentrations in Si Fermi-Dirac energy distribution function f n = + exp[(e E F ) / kt] Mass-action law np = n i 2 Concentration of majority carriers (room temperature) N-type: N D P-type: N A Intrinsic carrier concentration: n i = A exp( E g 2kT ) Intrinsic temperature: about 200ºC P-N junction device (diode) 6

7 MOS device ( metal-oxide-semiconductor) Controllable resitance Fast switch Signal amplifier J. P. Uyemura, Fundamentals of MOS Digital Integrated Circuits, Addison, 989. The integrated circuit concept: planar technology Patent de Jack Kilby, Nobel 2000 Intel Pentium II J. P. Uyemura, Fundamentals of MOS Digital Integrated Circuits, Addison,

8 Moore s law : the number of integrable devices in a single Semiconductor crystal duplicates each 8 months Evolucion Evolucion of thememorias capacity ofdram DRAMs EvolutionEvolución of the complexity of CIsde(Moore s de la complejidad los CI's Law) (Mbits) , , Año Dimension critica (λ ) Photolithography critical dimension (λ) (micras) 2,5 0, Intel

9 Evolution of the integrated circuits 958 Kilby s integrated circuit 96 First planar process IC IC area increasing factor, D 2, 200 Critical dimension reduction factor, λ, /00 Packaging efficiency, PE, 50 Increasing of reliability Reduction of cost per device Improvement of relation consumption/delay IBM 70nm transistor.2 volts, 27 ps Pentium 4, 0.8 microns 42 million transistors N = λ 2 D 2 PE = 0 8 Effects of the miniaturization area L 2 volume L 3 MECHANICS force area L 2 deformation L mass volume L 3 acceleration force / mass L - frequency acoustic speed / length L - time frequency - L speed acceleration.time Constant power force speed L 2 frictional force L 2 THERMODYNAMICS heat capacity volume L 3 thermal conductance L thermal constant time L 2 Feynman R.P. There s plenty of Room at the Bottom Eng. And Sci., 23:22-36, 960 Drexler, K., Nanosystems, John Wiley and Sons, 992 ELECTROSTATICS voltage electrostatic length length L electrostatic force area (E) 2 L 2 resistance length / area L - ohmic current voltage / current L 2 electrostatic energy L 3 capacitance energy / (voltage) 2 L magnetic energy Volume (B) 2 L 5 inductance energy / (current) 2 L ELECTRODYNAMICS inductive time constant Ind / R L 2 capacitive time constant R C Constant ELECTRONIC CIRCUIT MOS current L MOS resistance Constant MOS capacitance L MOS time constant L power consumption L 2 9

10 Evolution of the single bit transition energy Switching energy per gate (pj) Landauer88 JSSC Adiabatic Moore s Law limit? Landauer s prediction Adiabatic trend 0-7 ev ktln2 Year R. Landauer, Irreversibility and heat generation in the computing process, IBM, J. Res. And Dev., vol. 5, no. 3, pp. 83-9, July 96. Atoms per bit of memory V.V. Zhirnov and D. J. Herr, New Frontiers: Self-Assembly and Nanoelectronics, Computer, January 200, pp

11 International Technology Roadmap for Semiconductors, 200 International Technology Roadmap for Semiconductors, 200

12 Switching energy per gate (pj) Landauer88 JSSC Adiabatic Moore s Law limit? Landauer s prediction Adiabatic trend ev Year fj ktln2 Future evolution Bohr radius 50 pm ion Cu 2+ radius 73 pm H 2 bond length 74 pm C C bond length 20 pm C C bond length 35 pm C C bond length 50 pm ion S 2- radius 85 pm Cl 2 bond length 98 pm Si crystal lattice constant 540 pm gate exide thinness SiO 2, conventional technology, foresee year 200 nm = 000 pm layout resolution of an actual IC, 200, pm (0.2 micres) typical laateral length of an IC: 5 mm wavelength of a signal of 0 GHz: 30 cm International Technology Roadmap for Semiconductors, 2

13 Physical effects of the feature size reduction the feature size is reaching the mean free path of carriers the inelastic mean free path for silicon at room temperature is 00nm the feature size is getting close to the wavelength of electrons the wavelength of electrons carriers flowing parallel to surface is 8-0nm the feature size is close to the corresponding to the unitary doping volume bulk concept is given room to discrete system the feature size of the gate oxide (t ox ) is near of few molecule diameters the minimum t ox deviation causes important effects the tunnel effects of narrow barriers are becoming significant for 0.5 volts and a SiO 2 barrier of 3 nm the current density is 0-6 A/cm 2, while For.5 nm is A/cm > Implications 3