Query: 6H SiC raman spectroscopy wafer

Candidate papers:

abstract: Silicon carbide (SiC) is an important material used in semiconductor industries and nuclear power plants. SiC wafer implanted with H ions can be cleaved inside the damaged layer after annealing, in order to facilitate the transfer of a thin SiC slice to a handling wafer. This process is known as "ion cut" or "Smart Cut" It is worth investigating the exfoliation efficiency and residual lattice defects in H implanted SiC before and after annealing. In the present paper, lattice damage in the 6H SiC implanted by H2+ to a fluence of 5 x 1016 H2+/cm2 at 450 and 900 degC was investigated by a combination of Raman spectroscopy and transmission electron microscopy. Different levels of damage caused by dynamic annealing were observed by Raman spectroscopy and transmission electron microscopy in the as implanted sample. Atomic force microscopy and scanning white light interferometry were used to observe the sample surface morphology. Surface blisters and exfoliations were observed in the sample implanted at 450 degC and then annealed at 1100 degC for 15 min, whereas surface blisters and exfoliation occurred in the sample implanted at 900 degC without further thermal treatment. This finding can be attributed to the increase in the internal pressure of platelets during high temperature implantation. The exfoliation efficiency, location, and roughness after exfoliation were investigated and possible reasons were discussed. This work provides a basis for further understanding and improving the high efficiency "ion cut" technology.
author_names: Tao Wang

Zhen Yang

Bingsheng Li

Shuai Xu

Qing Liao

Fang-fang Ge

Tongmin Zhang

Jiaoli Li
title: Lattice Defects and Exfoliation Efficiency of 6H SiC via H2+ Implantation at Elevated Temperature
venue: Materials
year: 2020

abstract: Graphene has emerged recently as a new material with outstanding electronic properties1. This includes mass less Dirac fermions, ballistic transport properties at room temperature and good compatibility with silicon planar technology2. Different techniques have been developed in the last six years to fabricate mono or bi layer graphene. They range from exfoliated graphite, either mechanically1 or in a liquid phase solution3 to chemical vapor deposition on a metal surface4, and, more recently, to substrate free synthesis when passing ethanol into an argon plasma5. The method investigated in this work consists in a controlled sublimation of few atomic layers of Si from a single crystal SiC substrate6. Such epitaxial growth of graphene (EG) seems to be the most suitable option for industrial applications but, for easy control, it necessitates either a large and homogeneous sheet of monolayer graphene (MLG) or few layers graphene (FLG) covering the full wafer surface. Basically, on both the Si and C faces of any SiC substrate, graphene grows selectively on some reconstructed parts of the surface. Controlling the growth means then controlling locally the surface reconstruction. At low pressure conditions (below 10 6 Torr) it remains challenging to grow FLG with homogeneous domains larger than few hundred nanometers on both faces7. The homogeneity can be increased by lowering the sublimation rate. It has been demonstrated on the Si face by working at high pressure under a noble gas atmosphere such as argon8,9. In this work10, the surface reconstruction of the C face during the Si sublimation is modified by covering the SiC substrate with a graphite cap. It leads to a strongly step bunched morphology with on few selected terraces the growth of long anisotropic graphene ribbons (5 mm wide and up to 600 mm long) Since the Raman fingerprint of Bernal stacked FLG depends strongly of the number of graphene layers11 and the absorbtance of FLG is almost independent of the wavelength and proportional to the number of graphene layers12, we combine micro Raman spectroscopy with micro transmission measurements to study the quality and thickness uniformity of these ribbons. We find that most of these ribbons are homogeneous monolayers or bilayers of graphene and that the thermal stress between the graphene layer and the 6H SiC substrate is relaxed by the formation of wrinkles. This combination of techniques is especially useful to discriminate without any ambiguity between a monolayer graphene and a misoriented bilayer because their Raman fingerprint are identical. The spectra and extinction coefficient of a monolayer, a Bernal stacked bilayer noted AB, and a misoriented bilayer noted AA' are shown in Figure 1.
author_names: Antoine Tiberj

Jean Roch Huntzinger

B Jouault

Bilal Jabakhanji

Jean Camassel

Nicolas Camara

Gemma Rius

Alessandra Caboni

Francesc Perez-Murano

Philipe Godignon

Narcis Mestres
title: Raman spectroscopy of long isolated graphene ribbons grown on the C face of 6H SiC
year: 2010

abstract: 6H silicon carbide (SiC) substrates were implanted with nitrogen and aluminum at different doses and annealed in the temperature range from 1300degC 1700degC. Micro Raman Spectroscopy (m RS) measurements were performed in two sample geometries (conventional plane view and cross sectional) Changes of the polytype from 6H to a cubic (SiC) 1 x AIN) x and influences in the 6H SiC wafer up to depths of 2mm were detected. The results obtained by crosssectional m RS are discussed in comparison to other results from Reflection High Electron Energy Diffraction (RHEED) Rutherford Backscattering (RBS) Auger Electron Spectroscopy (AES) Transmission Electron Microscopy (TEM) and Positron Annihilation Spectroscopy (PAS) measurements.
author_names: Dietrich Rudolf T Zahn

Th Werninghaus

M Thumer

Joerg Pezoldt

Viton Heera
title: Raman Spectroscopy Investigation of (SiC) 1 x (Ain) x Layers Formed by Ion Implantation in 6H SiC
year: 1996

abstract: A 6H SiC single crystal irradiated in channeling mode by 4 MeV C +3 and Si +3 ions at various doping levels have been examined by SEM and micro Raman spectroscopy in order to study the lattice distortions inflicted by the impinging ions. C ions create zones of strongly damaged regions, parallel to the front face of the wafer with width increasing with the amount of doping. As expected, Si has induced considerably more lattice distortions than C and almost two orders of magnitude less doping induces apparently the same effect as C. Despite the large laser spot size compared with the boundaries of the distorted regions, micro Raman data provided results agreeing with the SEM pictures and the Monte Carlo calculations using the SRIM 2013 software. From the evolution of the crystalline peaks in the Raman spectra one can conclude that the impinging ions do not accommodate as defects in the lattice, but mostly displace the ions breaking the bonds and destroying the long range order.
author_names: Aikaterini Flessa

E Ntemou

Michael Kokkoris

Efthymios Liarokapis
title: Raman mapping of C and Si channeling implantation of SiC
year: 2020

abstract: Structural perfection of silicon carbide (SiC) single crystals is essential to achieve high performance power devices. A new bulk growth process for SiC proposed by researchers at NASA Glenn Research Center, called large tapered crystal (LTC) growth, based on axial fiber growth followed by lateral expansion, could produce SiC boules with potentially as few as one threading screw dislocation per wafer. In this study, the lateral expansion aspect of LTC growth is addressed through analysis of lateral growth of 6H SiC a/m plane seed crystals by hot wall chemical vapor deposition. Preliminary synchrotron white beam x ray topography (SWBXT) indicates that the as grown boules match the polytype structure of the underlying seed and have a faceted hexagonal morphology with a strain free surface marked by steps. SWBXT Laue diffraction patterns of transverse and axial slices of the boules reveal streaks suggesting the existence of stacking faults/polytypes, and this is confirmed by micro Raman spectroscopy. Transmission x ray topography of both transverse and axial slices reveals inhomogeneous strains at the seed epilayer interface and linear features propagating from the seed along the growth direction. Micro Raman mapping of an axial slice reveals that the seed contains high stacking disorder, while contrast extinction analysis (g*b and g*bxl) of the linear features reveals that these are mostly edge type basal plane dislocations. Further high resolution transmission electron microscopy investigation of the seed homoepilayer interface also reveals nanobands of different SiC polytypes. A model for their formation mechanism is proposed. Finally, the implication of these results for improving the LTC growth process is addressed.
author_names: Ouloide Yannick Goue

Balaji Raghothamachar

Yu Yang

Jianqiu Guo

Michael Dudley

Kim Kisslinger

Andrew J Trunek

Philip G Neudeck

David J Spry

Andrew Allan Woodworth
title: Study of Defect Structures in 6H SiC a/m Plane Pseudofiber Crystals Grown by Hot Wall CVD Epitaxy
venue: Journal of Electronic Materials
year: 2015

abstract: Thin and homogeneous epitaxial graphene (EG) layers on a 6H SiC (000) substrate are fabricated and they cover the whole substrate (10 x 10 mm2) The sample surface is capped by another 6H SiC (000) wafer in a graphite enclosure to form a relatively high Si partial pressure between them, which significantly reduces the extremely high growth rate of EG. The structure and morphology of the EG layers are investigated by Raman spectroscopy, atomic force microscopy and field emission scanning electronic microscopy. The results are compared with an uncapped sample surface, and reveal the obvious existence of ridges on the surface of the EG, and show that capping is indeed beneficial to obtain homogeneous graphene.
author_names: Deng Pengfei

Lei Tianmin

Lu Jin-jun

Liu Fu-Yan

Zhang Yuming

Guo Hui

Zhang Yi-men

Wang Yuehu

Tang Xiaoyan
title: Fabrication of Thin Graphene Layers on a Stacked 6H SiC Surface in a Graphite Enclosure
year: 2013

abstract: The epitaxial graphene on the 4Hor 6H SiC(0001) surface has been intensively studied due to the possibility of wafer scale growt. However the existence of interface layer (zero layer graphene) and its influence on the upper graphene layer have been considered as one of the main obstarcles for the industrial application. Among various methods tried to overcome the strong interaction with the substrate through the interface layer, it has been proved that the hydrogen intercalation successfully passivate the Si dangling bond of the substrate and can produce the quasi free standing epitaxial graphene (QFEG) layers on the siC(0001) surface. In this study, we report the results of the angle resolved photoemission spectroscopy (ARPES) and Raman spectroscopy for the QFEG layers produced by ex situ and in situ hydrogen intercalation.From the ARPES measurement, we confirmed that the Dirac points of QFEG layers exactly coincide with the Fermi level. The band structure of QFEG layer are sustainable upon thermal heating up to 1100 K and robust against the deposition of several metals andmolecular deposition. We also investigated the strain of the QFEG layers by using Raman spectroscopy measurement. From the change of the 2D peak position of graphene Raman spectrum, we found out that unlike the strong compressive strain in the normal epitaxial graphene on the SiC(0001) surface, the strain of the QFEG layer are significantly released and almost similar to that of the mechanically exfoliated graphene on the silicon oxide substrate. These results indicated that various ideas proposed for the ideal free standing graphene can be tested based on the QFEG graphene layers grown on the SiC(0001) surface.
title: Angle Resolved Photoemission Spectroscopy and Raman Spectroscopy Study on the Quasi free Standing Epitaxial Graphene on the 4H SiC(0001) surface
year: 2013

abstract: Abstract 6H SiC has been produced via catalyst free chemical vapor growth method using Si wafer and activated carbon powder as the respective Si and C sources. The effects of heating temperature (1250, 1300, and 1350 degC) and crucible height (9, 13, and 16 cm) on the formation of nanowires and nanoneedles have been systematically investigated. Scanning and transmission electron microscopy, X ray diffraction (XRD) Raman and photoluminescence (PL) spectroscopy have been employed in this study. The reasons for the transformation of nanoneedles to nanowires have also been proposed.
author_names: Kuan Yew Cheong

Zainovia Lockman
title: Effects of temperature and crucible height on the synthesis of 6H SiC nanowires and nanoneedles
year: 2009

abstract: Abstract Freestanding graphene on a trench has been fabricated extensively using a transfer process of chemical vapor deposition grown graphene. Here, we demonstrate that freestanding graphene can be grown directly on a trench without a transfer process. A shallow trench was made on a 6H SiC(0001) wafer using a focused ion beam lithography. The shallow trench was heated to a high temperature under Ar atmosphere. The heat treatment made the shallow trench become deeper and wider. Subsequently, epitaxial graphene was floating on the trench, resulting in freestanding graphene, where underlying bulk SiC was self etched after the growth of epitaxial graphene. The freestanding graphene on a trench was characterized using Raman spectroscopy and atomic force microscopy. Such freestanding graphene writing can be applied to semiconductor fabrication process of freestanding graphene devices without a transfer process.
author_names: I B Khadk

Junyoung Son

H -W Kim

D-H Lee

B -J Kim

Dain Sung

Geun-Yeong Yeom
title: Freestanding graphene writing on a silicon carbide wafer
year: 2020

abstract: Raman spectroscopy has been used to investigate wafers of both 4H SiC and 6H SiC. The wafers studied were semi insulating and n type (nitrogen) doped with concentrations between 2.1x1018 and 1.2x1019 cm 3. Significant coupling of the A1 longitudinal optical (LO) phonon to the plasmon mode was observed. The position of this peak shows a direct correlation with the carrier concentration. Examination of the Raman spectra from different positions on the wafer yielded a rudimentary spatial map of the carrier concentration. These data are compared with a resistivity map of the wafer. These results suggest that Raman spectroscopy of the LO phonon plasmon mode can be used as a noninvasive, in situ diagnostic for SiC wafer production and substrate evaluation.
author_names: J C Burton

L Sun

Milan Pophristic

S J Lukacs

Frederick H Long

Zhe Chuan Feng

Ian T Ferguson
title: Spatial characterization of doped SiC wafers by Raman spectroscopy
year: 1998