Towards Graphene-based heterojunction devices for microelectronic applications

Transcription

1 Towards Graphene-based heterojunction devices for microelectronic applications IHP GmbH Leibniz (Innovations for High Performance Microelectronics) TU-Dresden/IHM (Institute of Semiconductors and Microsystems) Ch. Wenger, C. A. Chavarin, G. Lupina, C. Strobel, M. Junige, J. Kitzmann, M. Lukosius, M. Albert, J.W. Bartha G. Lippert, Dabrowski DFG BA 2009/6-1 & WE 3594/5-1 DFG ME 4117/1

2 Agenda 1 Motivation 2 Graphene Synthesis on Germanium 3 Deposition of amorphous Silicon on transferred Graphene 4 Deposition of dielectrics on transferred Graphene 5 Summary 2

3 Motivation: Graphene driver for speed? class 1; 900m², 130nm SiGe:C;Bi-CMOS Systems Technology Circuits Materials Graphene-based transistors may crossing the THz barrier Many fundamental and critical questions on the atom-scale level IEDM 12/2010 f T /f max of 300 GHz/500 - B. Heinemann et al; f max 798 GHz - GeorgiaTech/IHP at 4.3 Kelvins

4 IHP: Research Roadmap (from 2013) SemiCon 11/17 15 Nov

5 Graphene Base High-Frequency Transistor Graphene based transistor way to THz? Simulations predict up to 3 THz Opens a way to combine electronic + optical functions on chip Goal: f T > 100 GHz S. Vaziri, Nano Lett. 13, 1435 (2013) W. Mehr et al., Vertical Graphene Base Transistor. IEEE Electron Device Letters 33, 691 (2012). 5

6 Intermediate goal: Graphene toolbox toolbox of process and metrology tools enabling fabrication of a variety of graphenebased devices on 200 mm wafers in a CMOS pilot line In collaboration with universities + industry November 20,

7 Transferred Graphene on 200 mm Silicon wafers SEM investigation of transferred CVD graphene on SiO 2 /Si wafer ML + few layer graphene on 200mm wafer Defects (i.e. grain boundaries) visible November 20,

8 Residual contamination of transferred Graphene time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) Regardless of the transfer method and associated cleaning ToF-SIMS + TR-XRF indicate contaminants (Cu,Fe) These metal impurities partially mobile upon thermal treatment Residual Metallic Contamination of Transferred Chemical Vapor Deposited Graphene G. Lupina* et al IHP, Im Technologiepark 25, Frankfurt, Germany; KTH Royal Institute of Technology, Sweden; Institute of Electronic Materials Technology, Warsaw, Poland; University of Siegen, Germany; Infineon Technologies AG, Regensburg 93049, Germany; Infineon Technologies Dresden GmbH, Germany; ACS Nano, 2015, 9 (5), pp November 20,

9 Growth of graphene onto structured Ge/SiO 2 substrate Ge-GBHT: Si replaced with Ge (direct graphene growth) elimination of graphene transfer Chemical interaction of C atoms with substrate during growth V. Di Lecce, Trans. Electron Dev., 60, 4263 (2013) Ge Graphene Ge Si EP , Intensity (arb. units) graphitic carbon Ge substrate SiC R.W. Olesinski and G.J. Abbaschian; Si substrate Bulletin of Alloy Phase Diagrams Vol. 5 No XPS of carbon deposition on Ge and Si XPS: C 1s Binding energy (ev) Ge pillars (2µm) on Si embedded in SiO 2 On SiO 2 no graphene detectable Ge islands indicating graphene G. Lippert et al; CA R B O N 7 5 ( ) Raman spectra + 2D/G mode intensity map G. Lippert et al., Carbon 75, 104 (2014). 9

10 CVD vs. MBE nucleation of Graphene on Germanium C 2 H 4 may adsorb dissociatively H diffuses out H-saturated graphene edge is passive Graphene molecule (29 atoms) on Ge(001) CVD: C atoms terminated with H, and some bond substrate weakly Clean graphene edge is bonded to Ge(001) MBE: C atoms bonds with the substrate 10

11 MBE grown graphene on germanium SEM image of coated Germanium/Si (001) Bright charged e beam of SEM Dark area indicate graphene Orange circle measured by 4tip STM Response of conductance (drain current) on gate voltage UHV-CVD grown graphene o Charge neutrality point indicates p-doping o Mobility: 1500 cm²/v.s MBE grown graphene o Weakly p-doped o Mobility: 650 cm²/v.s 11

12 Raman mapping Graphene on Germanium UHV-CVD vs. MBE (a) 130 spectra from a CVD (average in black) D, G, and 2D in unstrained + undoped graphene indicated (b) 2D vs. G illustrating the difference in doping + strain MBE CVD Compressive MBE film (-0.3%) thermal expansion [graphene (-3x10-6 K -1 ) + Ge (6x10-6 K -1 )] because graphene film forming on the interfacial graphene-like layer grows under tensile strain. CVD film remains in direct contact with Ge(001), is tensile Indicating that strain in growing graphene is tensile + higher than +0.4% (measured at T room ). 12

13 Graphene IHP 200 mm wafers Graphene CVD (Aixtron BM 300T) Tool integrated into the cleanroom toolset 200 mm Graphene available on Ge and Ni November 20,

14 Graphene on Ge 14

15 Ge/Si Transfer by Electrochemical Delamination Rq(0.64nm) Large area transferring possible 15

16 Improving nucleation on graphene by FDTS pre-treatment Without FDTS pre-coating With FDTS pre-coating Deposition of HfO 2 on graphene is inhomogenous caused by weak vdw binding forces Generation of seeds on graphene (FDTS NF 3 treatment) results into confirm coverage The quality of graphene is not affected Perfluorodecyltrichlorosilane-based seed-layer for improved CVD of ultrathin HfO 2 films on graphene J. Kitzmann, A. Göritz, M. Fraschke, M. Lukosius, Ch. Wenger, A. Wolff, G. Lupina Sci Rep. 2016; 6: November 20,

17 Modified CVD of amorphous Silicon on Graphene Deposition technique for n-type silicon on graphene Without damaging the electronic structure of graphene GFET VHF PEVCD extremly soft deposition technique Frequencies up to 200 MHz 10 nm SEM of Si on graphene: 30 nm Soft deposition M.Heintze, R.Zedlitz, Journal of Non-Cryst. Solids (1996)

18 Electrical characterization of graphene/(n)-a-si:h junctions GBHT-Transistor Diode Graphene/(n)-a-Si:H diode as core element of the GBHT CVD-grown graphene on Cu transferred to ZnO:Al a-si:h n-layers deposited with VHF-PECVD (140 MHz) contacts except graphene/(n)-a-si:h junction are ohmic threshold voltage (V F ) of graphene/(n)-a-si:h junction increased to reference ZnO:Al/(n)-a-Si:H Rectification ratio 1.6x10 4 (± 1 V) qφ B? 11/20/

19 Summary IHP and IHM develop processing modules for graphene electronic devices With a vision of integrating them in the backbone BiCMOS technology Current activities focused on the development of a baseline graphene technology - graphene synthesis on Germanium - deposition of silicon and dielectrics on graphene Graphene/(n)-a-Si:H diodes as core element of the high-frequency graphenebase heterojunction transistor (GBHT) were investigated 19

20 This work is dedicated to the memory of Prof. Wolfgang Mehr, the inventor and the pioneer of research on graphene base transistors. Thank you for your attention! Christian Wenger (Gunther Lippert) IHP Innovations for High Performance Microelectronics Im Technologiepark Frankfurt (Oder) Germany Phone: +49 (0) Fax: +49 (0)

21 Graphene growth on epitaxial Ge (001) film NanoARPES : * Dirac cone quality * Size of graphene grains * Orientation of the grains The nanoarpes map shows a continous Gr film Average qraphene grain size 3-4 µm NanoARPES map (15 x 15 µm) of density of state at E F (step width < 100nm) The graphene grains are preferenctially oriented along two high symmetry directions. arxiv