Fundamentals of Nanoelectronics: Basic Concepts

Transcription

1 Fundamentals of Nanoelectronics: Basic Concepts Sławomir Prucnal FWIM Page 1

2 Introduction Outline Electronics in nanoscale Transport Ohms law Optoelectronic properties of semiconductors Optics in nanoscale Band gap Quantum confinement effect Page 2

3 Photolithography Ion implantation Etching Temporary Gate Formation Silicon wafer metalization Page 3

4 Introduction NEAR-TERM Scaling of Si CMOS - Implementation of fully depleted SOI Implementation of high-mobility CMOS channel materials Page 4

5 SmartCut Introduction SIMOX process SOI Page 5 From Wikipedia

6 Introduction Silicon wafer technique/physical-verification-design-finfet-fd-soi/ &h=532&w=980&tbnid=bg2t-9aazopmjm:&tbnh=90&tbnw=166&usg= 3fSXT57run64yrsHWP2cDxmXjfs=&docid=9ZIFDJ9SQcwv AM&sa=X&ved=0CEAQ9QEwBWoVChMIrqu3kfrAxwIVw7kUCh3DKQn5 (Source: Synopsys) Page 6

7 Introduction technique/physical-verification-design-finfet-fd-soi/ &h=532&w=980&tbnid=bg2t-9aazopmjm:&tbnh=90&tbnw=166&usg= 3fSXT57run64yrsHWP2cDxmXjfs=&docid=9ZIFDJ9SQcwv AM&sa=X&ved=0CEAQ9QEwBWoVChMIrqu3kfrAxwIVw7kUCh3DKQn5 (Source: Synopsys) Page 7

8 Introduction The main manufacturing challenges for finfets (above 20 nm) are: - controlling the etch along the edges - uniform doping of 3D surfaces - Deposition of all the films used in the gate stack Benefits reduction in power consumption (~50% over 32nm) Faster switching speed Availability of strain engineering Challanges Very restrictive design options Fin width variability and edge quality leads to variability in threshold voltage V T Extra manufacturing complexity and expense Page 8

9 Fully depleted silicon-on-insulator FD-SOI vs PD-SOI The top silicon layer is typically between 50 and 90 nmthick Silicon under the channel is partially depleted of mobile charge carriers. The top silicon layer is between 5 and 20 nm thick, typically ¼ of the gate length Silicon under the gate is fully depleted of mobile charge carriers. There is no floating body effect. Page 9

10 Introduction Fully depleted silicon-on-insulator FD-SOI (below 14 nm) Benefits Significant reduction in power consumption below 11 nm Faster switching speed Easier, standard manufacturing process Challanges High cost of initial wafers Variability in V T due to variations in the thickness of silicon thin-film No strain engineering possible Availability of back-biasing to control V T No doping variability Page 10 10

11 Introduction NEAR-TERM Scaling of Si CMOS - Implementation of fully depleted SOI Implementation of high-mobility CMOS channel materials LONG-TERM Implementation of advanced multi-gate structures ultra-thin body multi-gate MOSFETs Page 11

12 Multi-gate structures jpg%253f blob%253dnormal&imgrefurl=http%3a%2f%2fwww.fz-juelich.de%2fpgi%2fpgi-9%2fde%2fforschung%2f05-si-nano-mosfet%2f01-multigate%2520nanowire%2f_node.html&h= 336&w=600&tbnid=4kA-VMzzxXDUlM%3A&docid=ZqBKi7JKfbji2M&ei=OrjaVbjkF4n0ULaHjdAE&tbm=isch&iact=rc&uact=3&dur=2146&page=1&start=0&ndsp=30&ved=0CHQQrQMw GmoVChMIuOnjrIrBxwIVCToUCh22QwNK Page 12

13 Multi-gate structures Page 13

14 Hybrid 1D and 3D nanostructures Room temperature semi-logarithmic I-V characteristic of n-inas/p-si heterojunction. AFM topography of annealed and etched sample Prucnal et al. Nanolett. 11, 2814, (2011) Page 14

15 Hybrid 1D and 3D nanostructures InAs Page 15

16 Hybrid 1D and 3D nanostructures Page 16

17 Current (A) GeOI for junctionless transistors x100x3000 nm H x W x L 100 nm Ge 50 nm Ge x50x3000 nm H x W x L Voltage (V) Page 17

18 Electronic transport Page 18

19 3 cm 300 length scale: transistor density 1 mm = 1m/ mm channel length 1 mm = 1mm/ < 100 nm 2015 < 20 nm 1 nm = 1mm/1000 Atomic distance < 1 nm For the channel length of 10 mm size of transisotr is 100 mm 3 cm Page 19

20 3 cm length scale: transistor density 1 mm = 1m/ mm channel length 1 mm = 1mm/ < 100 nm 2015 < 20 nm 1 nm = 1mm/1000 Atomic distance < 1 nm For the channel length of 100 nm size of transisotr is 1 mm 3 cm Page 20

21 3 cm length scale: transistor density 1 mm = 1m/ mm channel length 1 mm = 1mm/ < 100 nm 2015 < 20 nm 1 nm = 1mm/1000 Atomic distance < 1 nm For the channel length of 20 nm size of transisotr is 200 nm 3 cm Page 21

22 length scale:electronic transport 1 mm = 1m/ mm 1 mm = 1mm/ < 100 nm 2015 < 20 nm 1 nm = 1mm/1000 Atomic distance < 1 nm S V o - + Channel V I =R I D R determines On/Off state and is controlled by 3 rd terminal Page 22

23 length scale:electronic transport 1 mm = 1m/ mm 1 mm = 1mm/ < 100 nm 2015 < 20 nm 1 nm = 1mm/1000 Atomic distance < 1 nm S e V o - + Channel I e D Diffusive transport Page 23

24 length scale:electronic transport 1 mm = 1m/ mm 1 mm = 1mm/ < 100 nm 2015 < 20 nm 1 nm = 1mm/1000 Atomic distance < 1 nm S e V o - + Channel I e D Ballistic transport Page 24

25 length scale: Ohms law S ~mm ~nm V o Channel D S V - + V =R I I W V - V o Channel L + I =R= ρ W L I D I =R= ρ W (L + m eanf ree p ath ) R=r L A, L 0, R 0, R = h q 2=25kW for ballistic transport Page 25

26 length scale: Ohms law G. Jo et al. J. Appl. Phys. 102, (2007) Page 26

27 Mobility Page 27

28 length scale: mobility Page 28

29 length scale: mobility Ballistic transport Diffusive transport F Gámiz 2004 Semicond. Sci. Technol Page 29

30 length scale: mobility Patrick S. Goley * and Mantu K. Hudait Materials 2014, 7(3), Page 30

31 Mobility cm 2 /Vs Mobility cm 2 /Vs GeOI for junctionless transistors SmartCut GeOI Epi-Ge University of Tokyo hole mobility for 50 nm Ge PECVD+FLA HZDR 0 2.0x x x x x10 19 Carrier concentration (cm -3 ) Carrier mobility vs. Carrier concentration in 50 nm thick Ge on insulator. 500 Electron mobility for 50 nm Ge Preliminary data SmartCut GeOI Epi-Ge University of Tokyo PECVD+FLA HZDR Xiao Yu, et all. ECS Solid State Lett., 4, P15, (2015) Page Carrier concentration (cm -3 )

32 Downscaling Page 32

33 Optoelectronic properties of semiconductors Douglas J Paul, Semicond. Sci. Technol. 19, R75-R108 (2004) Page 33

34 Optoelectronic properties of semiconductors IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 55, NO. 1, JANUARY 2008 Page 34

35 Optical properties of semiconductors Page 35

36 Optical properties of semiconductors k=0 (a) Direct-bandgap semiconductors such as GaAs, InP and GaN. (b) An indirect-bandgap semiconductor, such as silicon or germanium. k 0 Page 36

37 Optical properties of semiconductors Page 37

38 Optical properties of semiconductors Ge with direct bandgap Direct bandgap energies of unstrained Ge 1 x Sn x alloys (a) and calculated band edges of the various bands for pseudomorphic Ge 1 x Sn x alloys on Ge as a function of Sn composition. Jia-Zhi Chen, et al., Opt. Mater. Express 4, (2014) Page 38

39 Optical properties of semiconductors Schematic of the effect of quantum confinement on the electronic structure of a semiconductor. The arrows indicate the lowest energy absorption transition. (a) Bulk semiconductor CB = conduction band; VB = valence band). (b) Three lowest electron (En le ) and hole (En lh ) energy levels in a quantum dot. The corresponding wave functions are represented by dashed lines. (c) Semiconductor nanocrystal (quantum dot). Page 39

40 Optical properties of semiconductors (a) Three lowest electron (En le ) and hole (En lh ) energy levels in a semiconductor nanocrystal quantum dot. The corresponding wave functions are represented by the dashed lines. Allowed optical transitions are given by the arrows. (b) Assignment of the transitions in the absorption spectrum of colloidal CdTe quantum dots. Page 40

41 Optical properties of semiconductors Energy of photons emitted by QDs E g = band gap energy of bulk semiconductor; R = radius of quantum dot; m e* = effective mass of excited electron; m h* = effective mass of excited hole; h = Planck s constant. Page 41

42 Optical properties of semiconductors Energy of photons emitted by QDs CdS QD 1. Experimental data 2. calculation E g = band gap energy of bulk semiconductor; R = radius of quantum dot; m e* = effective mass of excited electron; m h* = effective mass of excited hole; h = Planck s constant. Page 42

43 Optical properties of semiconductors Energy of photons emitted by QDs E g = band gap energy of bulk semiconductor; R = radius of quantum dot; m e* = effective mass of excited electron; m h* = effective mass of excited hole; h = Planck s constant. "Advanced Biomedical Engineering", book edited by Gaetano D. Gargiulo, Coeditor: Alistair McEwan, ISBN , Page 43

44 Optical properties of semiconductors Bohr radius for semiconductors a* b = ε m μ a b a b =0.053 nm dielectric constant m electron mass m effective electron mass Schematic representation of the quantum confinement effect on the energy level structure of a semiconductor material. Celso de Mello Donegá, Chem. Soc. Rev., 40, (2011) Page 44

45 Questions?? Page 45