Graphene-Si Heterogeneous Nanotechnology: Towards Practical VLSI Adoption

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1 nanohub User Conference, 2014 Graphene-Si Heterogeneous Nanotechnology: Towards Practical VLSI Adoption Deji Akinwande Department of Electrical and Computer Engineering The University of Texas Austin, U.S.A #1

2 My first experience with nanohub, RTD simulator on nanohub developed by Dr. Michael McLennan, >1000 users #2

3 #3 Graphene - A single honeycomb sheet of carbon atoms - Thinnest known material - Outstanding electrical, optical, thermal, mechanical, and chemical properties Nobel Prize in Physics

4 Evolution Revolution #4 Grand Applications of Graphene The 2 Main Possibilities Heterogeneous Si-based Wafer-scale Integration Flexible Nanotechnology 2009 Graphene on 0.25um CMOS 2011 Flexible 2D FETs

5 #5 Outline Wafer-scale Graphene Growth Graphene Raman Metrology Graphene Electronics

6 Vision for Wafer-Scale Graphene Technology Wafer-scale Metrology #6 1. Wafer scale growth Cu foil, {Cu,Co,Ni} films, SiC? Si 2. Wafer scale transfer Polymer transfer, delamination, bonding? Si growth wafer 3. Wafer scale circuits Si, Si CMOS, Qz?

7 1. Wafer-Scale Graphene Growth Aixtron Black Magic System (Academic-Industry partnership) Capabilities 4 wafer capability CVD or PECVD growth mode Pulsed plasma control Independent vapor and substrate temperature control CH 4, C 2 H 2, and C 2 H 4 precursors Automated computer control for routine repeatability #7

8 1. Wafer Scalable Graphene Growth on Si Scalable Process Flow (Tao et al., ACS Nano, 2012.) Evaporate Cu High-T H 2 anneal Hydrogen SiO 2 Si a-cu SiO 2 Si (111) Cu SiO 2 Si XRD a-cu 0.1 μm ~20 μm crystallized Cu grains amorphous Cu (111) 10 μm #8

9 Wafer Scale Growth: Microscopy STM Image TEM Image Epoxy Graphene SiO 2 Benefits of H 2 : Promotes Cu (111) formation, Serves as self-limiting co-catalyst #9

10 #10 Outline Wafer-scale Graphene Growth Graphene Raman Metrology Graphene Electronics

11 Raman as a tool to characterize graphene #11 In-plane Out-of-plane

12 Characteristic Raman fingerprint of graphene #12 Unambiguous, high-throughput, non destructive identification of graphene layers and quality 2D peak ~2660 cm -1 G peak ~1580 cm -1 D peak ~1330 cm -1 Important Raman Metrics i- 2D/G Ratio ii- Full-width at half-maximum (FWHM) of 2D peak iii- D/G Ratio

13 2. Wafer-Scale Graphene Metrology GRISP Raman Metrology Software on nanohub, (Babenco et al., SPIE, 2012) M. Babenco, 2011 International exchange student #13

14 Wafer-Scale Graphene Metrology Basic features of GRISP i. Baseline removal (median filter) G 2D ii. Data smoothing (mean filter) G 2D iii. Curve fitting (Lorentzian fitting) iv. Mapping Babenco et al., SPIE, 2012 #14

15 #15 Intensity (a.u) Wafer-Scale Graphene Characterization D G L T C B Tao et al., JPC-C, 2012 R 2D T L b 2D/G Raman maps of graphene R B T L c D/G R B Graphene Metrology

16 #16 300mm Wafer-Scale Growth with Aixtron BM AIXTRON Cambridge 300mm 300 mm 150 mm 100 mm

17 170 users to April 14 ~7-8 users/month #17 Wafer-Scale Graphene Metrology GRISP Raman Metrology Software on nanohub, (Babenco et al., SPIE, 2012) Usage of GRISP

18 #18 Wafer-Scale Graphene Metrology Usage of GRISP ~70% of users from USA and India ~50-60% of users from Educational Institutions

19 #19 Outline Wafer-scale Graphene Growth Graphene Raman Metrology Graphene Electronics

20 Wafer-Scale Graphene Transfer to SiO 2 /Si Evaporate Cu High-T H 2 anneal High-T CH 4 growth a-cu (111) Cu (111) Cu SiO 2 SiO 2 SiO 2 SiO 2 Si Etch PMMA Si Transfer graphene Si PMMA Si Etch Cu insulator insulator insulator Final substrate G patterned on final wafer Final substrate Final substrate Graphene channels ~ 40,000 devices on a 100 mm wafer mobility: 2,000-10,000 cm 2 /Vs #20

21 State-of-the-art CVD Graphene FETs on SiO 2 /Si GFET measured in ambient conditions Voltage (V) Measured Data Model Fitting R ( ) µ h ~17,776 µ e ~17, V g -V dirac (V) Amplifier 15x input E-04-5.E-05 0.E+00 5.E-05 1.E-04 Maximum mobilities of ~18,000cm 2 /V-s Time (s) Current saturation & secondary linear region observed output V d = 5V, f~12 khz #21

22 Outlook and Challenges for Graphene VLSI R (Ω) Materials Cu grain size ~20um 66um 20 µm 50um Process Wafer-bonding G bonding transfer to SiO 2 /Si Devices 2,000 μ~14,000cm 2 RT 1, Vg (V) + Sensors + THz + Photonic + Thermal devices #22

23 NASCENT NERC: A new center to address nanomanufacturing challenges New 10yr NSF NERC Grant

24 ACKNOWLEDGEMENTS Research Staff #24

25 #25 ACKNOWLEDGEMENTS Collaborators -Dr. Rod Ruoff -Dr. A. Dodabalapor -Dr. Sanjay Banerjee 25