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See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/237064425 Conference presentation Data · June 2013 CITATIONS READS 0 50 4 authors , including: Andrea Severino C. Locke STMicroelectronics University of South Florida 103 PUBLICATIONS 715 CITATIONS 33 PUBLICATIONS 299 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: CHALLENGE: 3C-SiCHetero-epitaxiALLy grown on silicon compliancE substrates and new 3C-SiC substrates for sustaiNable wide-band-Gap powEr devices View project WINSiC4AP, in the frame of ECSEL Calls 2016-1 call View project All content following this page was uploaded by F. La Via on 06 June 2014. The user has requested enhancement of the downloaded file.

High Quality Cubic Silicon Carbide (3C-SiC) for MOS Applications A. Severino, F. La Via IMM-CNR, sezione di Catania, Stradale Primosole 50, 95121, Catania, Italy C. Locke, S.E. Saddow University of South Florida, EE Dept., 4202 E. Fowler Ave., 33625, Tampa, FL, USA IMM

Outline • Motivations for Silicon Carbide • Material Properties and Application Fields • 3C-SiC advantages and limitations • 3C-SiC heteroepitaxy • Growth process from thin to thick 3C-SiC films • Defects in 3C-SiC • On-axis vs Off-axis 3C-SiC films • Towards MOS - Preliminary observation at nanoscale • Conclusions and perspectives IMM

Motivations for SiC High E B Low on-state resistance High E g Low leakage current High ν SAT High working Low n i frequencies High κ High thermal capability RF APPLICATIONS HIGH POWER APPLICATIONS IMM

SiC advantages and drawbacks Advantages Drawbacks ü Anisotropy of important electrical ü Well-established CVD growth technique properties in hexagonal SiC (4H, 6H-SiC) ü Easy implementation of Si technology ü Chance to use SiO 2 as stable gate oxide ü Limited wafer size in hexagonal SiC ü Ability to grow p-type and n-type material ü Elevated costs required to grow high- ü 3C-SiC growth on low-cost large-area Si quality single crystal material substrates IMM

The 3C-SiC Polytype Thermodynamically stable at lower temperature • growth at reduced temperatures on large area Si substrates Good electrical properties • narrower bandgap energy (2.3 eV) • lower density of traps at SiC/SiO 2 interface • higher electron channel mobility • higher stability under electrical stress Good mechanical properties • high Young modulus (400-700 GPa) for high frequency MEMS • stable for high working temperatures (~650 °C) Lack of a bulk as substrate for 3C-SiC homoepitaxy Generation of stress and defects in 3C-SiC heteroepitaxy • electrically active crystallographic defects (STACKING FAULTS) • wafer bow IMM

High electron mobility for MOSFET realization Electron mobilities of monocrystalline bulk 6H-SiC and 3C-SiC thin films deposited on Si (100) off-axis towards (011) ‘Comparison of 6H-SiC, 3C-SiC and Si for Power Devices’ M. Bhatnagar, B.J. Baliga, IEEE Trans. On Electr. Dev. 40 (3), 645 (1993) ‘Fabrication of high performance 3C-SiC vertical MOSFETs’, H. Nagasawa et al. , Phys. Stat. Sol. b, 245 , No. 7, 1272 (2008) IMM

The Main Limitation: Stacking Faults STACKING FAULTS AFFECT STRONGLY THE LEAKAGE CURRENT OF P-N JUNCTION IMM

Growth Process • Horizontal HW/CW CVD Reactors Epitaxial Reactor MF2 • Multi-step Chemical Vapor Deposition Process Sited in USF Tampa • Various Chemistries • Several Si orientations – Off-axis surfaces • Modified/Compliant substrates IMM

Growth of thin films – The ‘ Carbonization Step ’ The initial stage of growth (buffer layer) depends on the experimental conditions Pressure and Temperature affect: 400 Torr Ø Nucleation density Ø Nucleation regime Ø Interface morphology Ø Surface morphology 760 Torr Ø Defect generation Ø Stress nature in the system IMM

Growth of thick films – Defects in 3C-SiC 20% lattice mismatch between a Si and a SiC generates several crystallographic defects 4000 (200) 3C-SiC FWHM (arcsec) 3500 High-defect density Worst film quality 3000 2500 2000 1500 1000 Low-defect density Better film quality 500 0 0 10 20 30 40 50 3C-SiC film thickness ( µ m) XRD Rocking Curve FWHMs on surface diffraction plane • Very high-density of crystallographic defects close to the interface • Better 3C-SiC quality by increasing film thickness Cross-section TEM of a thick 3C-SiC film (narrower Rocking Curve FWHM) E. Polychroniadis et al. , Journal of Crystal Growth 263, 68 (2004). A. Severino et al., Thin Solid Films, 518 , S165 (2010). IMM

Growth of thick films – The growth rate IN ORDER TO REALIZE 3C-SiC SUITABLE FOR ELECTRONIC DEVICES OR SENSORS DEFECT DENSITY MUST BE REDUCED AND CRYSTAL QUALITY IMPROVED Allowed by reducing the growth rate DEFECTS, SUCH AS MICRO-TWINS, REDUCE THEIR DENSITY AT LOWER GR IMM

Growth of on-axis thick films – Stacking Faults Tending to saturation Saturated regime attributed to annihilation/generation mechanism of SF? IMM

Growth of thick films – 3C-SiC film morphology ANTI-PHASE BOUNDARIES IN ON-AXIS FILMS MICRO-STEPS DETECTED ON BOTH FILMS STEP-BUNCHING RELATED MACRO STEPS ON OFF-AXIS FILMS ANISOTROPIC DISTRIBUTION OF STACKING FAULTS ON OFF-AXIS FILMS IMM

Growth of thick films – Stacking Faults LOWER STACKING FAULT LINEAR DENSITY WITH HIGHLY ANISOTROPIC DISTRIBUTION OF STACKING FAULTS IN OFF-AXIS FILMS IMM

Growth of thick films – Stacking Fault Density FWHM of (004) 3C-SiC Linear Density FWHM of (004) 3C-SiC Linear Density Rocking Curve // [1-10] of SF// [1-11] Rocking Curve // [110] of SF// [111] ON AXIS 3C-SIC FILM 349 arcsec 6.5 x 10 3 cm -1 380 arcsec 8 x 10 3 cm -1 OFF-AXIS 3C-SIC FILM 329 arcsec 6.5 x 10 3 cm -1 298 arcsec 2 x 10 3 cm -1 IMM

Oxidation of 3C-SiC films – Effect of Defects MAIN CRYSTALLOGRAPHIC DEFECTS AFFECT THE OXIDE UNIFORMITY AND INTERFACE ANTI-PHASE BOUNDARIES CAN BE ELIMINATED BY OFF-AXIS FILM GROWTH MICRO-TWINS ARE VANISHING FOR SUFFICIENT 3C-SIC THICKNESS STACKING FAULTS STILL SURVIVE IMM

Electrical Characterization at Nanoscale PRELIMINARY RESULTS NO EFFECT RELATED TO STACKING FAULTS OBSERVED LARGE SIGNAL VARIATION AT STEP IN SCM MAP DUE TO LARGER CONTACT AREA OF THE TIP OR TO A LOCAL ENHANCEMENT OF THE ELECTRIC FIELD OVER THE STEPS 5 nm SiO 2 uniform layer was thermally grown on 10 µ m 3C-SiC films (on and off-axis) by RTP Oxidation in N 2 -O 2 ambient at 1050°C followed by a RTA annealing at 800°C in pure Ar IMM

Experimental Flat-Band Voltage PRELIMINARY RESULTS LOW HYSTERESIS OBSERVED à à GOOD OXIDE PERFORMANCE NEGATIVE V FB SHIFT à à POSITIVELY CHARGED C-CLUSTER AND DANGLING BONDS HIGHER EXPERIMENTAL V FB SHIFT IN ON AXIS MATERIAL IMM

Summary • Silicon Carbide: excellent material properties but … • 3C-SiC heteroepitaxy on large area Si substrates • CVD growth process – from thin to thick 3C-SiC film growth • Buffer layer formation • The growth rate and film thickness on 3C-SiC film quality • SFs show a saturation for thick film growth • Influence of substrate orientation on SFs and morphology • Influence of defects on oxidation morphology • Preliminary electrical characteristic of MOS at nanoscale IMM

Acknowledgements • Dr. Andrea Canino for SEM analysis • Mr. Corrado Bongiorno for TEM analysis • Dr. Filippo Giannazzo for AFM and SCM analysis • Dr. Patrick Fiorenza for AFM and SCM analysis IMM View publication stats View publication stats