scholarly journals Breakdown Degradation Associated With Elementary Screw Dislocations In 4H-SiC P+N Junction Rectifiers

1997 ◽  
Vol 483 ◽  
Author(s):  
P. G. Neudeck ◽  
W. Huang ◽  
M. Dudley
Keyword(s):  
Video Camera ◽  
Initial Study ◽  
Hollow Core ◽  
Power Devices ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
X Ray ◽  
Current Voltage ◽  
The Impact ◽  
Sic Wafer

AbstractIt is well-known that SiC wafer quality deficiencies are delaying the realization of outstandingly superior 4H-SiC power electronics. While efforts to date have centered on eradicating micropipes (i.e., hollow core super-screw dislocations with Burgers vector > 2c), 4H-SiC wafers and epilayers also contain elementary screw dislocations (i.e., Burgers vector = Ic with no hollow core) in densities on the order of thousands per cm2, nearly 100-fold micropipe densities. This paper describes an initial study into the impact of elementary screw dislocations on the reverse-bias current-voltage (I-V) characteristics of 4H-SiC p+n diodes. First, Synchrotron White Beam X-ray Topography (SWBXT) was employed to map the exact locations of elementary screw dislocations within small-area 4H-SiC p+n mesa diodes. Then the high-field reverse leakage and breakdown properties of these diodes were subsequently characterized on a probing station outfitted with a dark box and video camera. Most devices without screw dislocations exhibited excellent characteristics, with no detectable leakage current prior to breakdown, a sharp breakdown I-V knee, and no visible concentration of breakdown current. In contrast devices that contained at least one elementary screw dislocation exhibited a 5% to 35% reduction in breakdown voltage, a softer breakdown I-V knee, and visible microplasmas in which highly localized breakdown current was concentrated. The locations of observed breakdown microplasmas corresponded exactly to the locations of elementary screw dislocations identified by SWBXT mapping. While not as detrimental to SiC device performance as micropipes, the undesirable breakdown characteristics of elementary screw dislocations could nevertheless adversely affect the performance and reliability of 4H-SiC power devices.

Effects of Different Defect Types on the Performance of Devices Fabricated on a 4H-SiC Homoepitaxial Layer

2006 ◽  
Vol 911 ◽  
Author(s):  
Hui Chen ◽  
Balaji Raghothamachar ◽  
William Vetter ◽  
Michael Dudley ◽  
Y. Wang ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Basal Plane ◽  
Schottky Contacts ◽  
Device Performance ◽  
Hollow Core ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
Edge Dislocations ◽  
Sic Wafer ◽  
Koh Etching

AbstractAn 8° off-axis 4H-SiC wafer with circular Schottky contacts fabricated on a CVD grown 4H-SiC homoepitaxial layer was studied to investigate the influence of various defects, including small (closed-core) screw dislocations (Burgers vector of 1c or 2c), hollow-core (micropipes; Burgers vector larger than 2c), threading edge dislocations (from conversion of basal plane dislocations from the substrate into the epilayer), grain boundaries and triangular defects, on the device performance in the form of breakdown voltages. The defects were examined using synchrotron white beam x-ray topography (SWBXT) based techniques and molten KOH etching. The devices commonly contained basal plane dislocations, small screw dislocations and threading edge dislocations, the latter two of which could give rise to low breakdown voltages for the devices. In addition, less commonly observed defects such as micropipes, grain boundaries and triangular defects are much more destructive to device performance than closed-core screw dislocations and threading edge dislocations.

scholarly journals Non-Micropipe Dislocations in 4H-SiC Devices: Electrical Properties and Device Technology Implications

1998 ◽  
Vol 512 ◽  
Author(s):  
P. G. Neudeck ◽  
W. Huang ◽  
M. Dudley ◽  
C. Fazi
Keyword(s):  
Breakdown Voltage ◽  
Low Voltage ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Hollow Core ◽  
Screw Dislocations ◽  
Current Filaments ◽  
The Impact ◽  
Sic Wafer ◽  
Power Densities

ABSTRACTIt is well-known that SiC wafer quality deficiencies are delaying the realization of outstandingly superior 4H-SiC power electronics. While efforts to date have centered on eradicating micropipes (i.e., hollow core super-screw dislocations with Burgers vectors > 2c), 4H-SiC wafers and epilayers also contain elementary screw dislocations (i.e., Burgers vector = lc with no hollow core) in densities on the order of thousands per cm 2, nearly 100-fold micropipe densities. While not nearly as detrimental to SiC device performance as micropipes, it has been previously shown that diodes containing elementary screw dislocations exhibit a 5% to 35% reduction in breakdown voltage, higher pre-breakdown reverse leakage current, softer reverse breakdown I-V knee, and concentrated microplasmic breakdown current filaments when measured under DC testing conditions. This paper details the impact of elementary screw dislocations on the experimentally observed reverse-breakdown pulse-failure characteristics of low-voltage (< 250 V) small-area (< 5 × 10-4 cm2) 4H-SiC p+n diodes. The presence of elementary screw dislocations did not significantly affect the failure properties of these diodes when subjected to non-adiabatic breakdown-bias pulsewidths ranging from 0.1 μs to 20 μs in duration. Diodes with and without elementary screw dislocations exhibited positive temperature coefficient of breakdown voltage and high junction failure power densities well above the failure power densities exhibited by highly reliable silicon power rectifiers. This preliminary result, based on measurements from one wafer of SiC diodes, suggests that highly reliable low-voltage SiC rectifiers may be attainable despite the presence of elementary screw dislocations.

Studies of c-Axis Threading Screw Dislocations in Hexagonal SiC

2008 ◽  
Vol 1069 ◽  
Author(s):  
Yi Chen ◽  
Xianrong Huang ◽  
Ning Zhang ◽  
Govindhan Dhanaraj ◽  
Edward Sanchez ◽  
...  
Keyword(s):  
Ray Tracing ◽  
Grazing Incidence ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
X Ray ◽  
Back Reflection ◽  
Partial Dislocations ◽  
Ray Tracing Simulation ◽  
Vector Magnitude

ABSTRACTIn our study, closed-core threading screw dislocations and micropipes were studied using synchrotron x-ray topography of various geometries. The Burgers vector magnitude of TSDs can be quantitatively determined from their dimensions in back-reflection x-ray topography, based on ray-tracing simulation and this has been verified by the images of elementary TSDs. Dislocation senses of closed-core threading screw dislocations and micropipes can be revealed by grazing-incidence x-ray topography. The threading screw dislocations can be converted into Frank partial dislocations on the basal planes and this has been confirmed by transmission synchrotron x-ray topography.

High-resolution x-ray topography of dislocations in 4H-SiC epilayers

2007 ◽  
Vol 22 (4) ◽  
pp. 845-849 ◽  
Author(s):  
Isaho Kamata ◽  
Hidekazu Tsuchida ◽  
William M. Vetter ◽  
Michael Dudley
Keyword(s):  
Computer Simulation ◽  
High Resolution ◽  
Edge Dislocation ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
X Ray ◽  
Topographic Features ◽  
Different Shapes ◽  
Vector Direction ◽  
Simulation Results

Synchrotron x-ray topography with a high-resolution setup using 1128 reflection was carried out on 4H-SiC epilayers. Four different shapes of threading-edge dislocation according to Burgers vector direction were observed. The four types of threading-edge dislocation images were calculated by computer simulation, and the experimental results correlated well with the simulation results. The detailed topographic features generated by plural screw dislocations and basal plane dislocations were also investigated.

X-Ray Topography Of A Single Superscrew Dislocation In 6H-SiC Through All {100} Faces

1996 ◽  
Vol 442 ◽  
Author(s):  
W. M. Vetter ◽  
M. Dudley
Keyword(s):  
Single Crystals ◽  
Semiconductor Devices ◽  
Image Contrast ◽  
Hexagonal Prism ◽  
Burgers Vector ◽  
X Ray ◽  
Stress Components ◽  
Sic Wafer

AbstractMicropipes, the hollow cores of superscrew dislocations that lie along the c-direction in SiC single crystals, are quite deleterious to the performance of semiconductor devices. In the x-ray topography of longitudinal-cut samples of these crystals, topographs in the reflection (006) show dislocation image contrast associated with the superscrew dislocations lying along the c-axis of the crystal, which is also the direction of the dislocations' Burgers vectors. In the (110) reflection, whose g-vector is perpendicular to the c-axis and the dislocations' Burgers vector, there is also an image of the superscrew dislocation formed, albeit weaker than the corresponding image in the (006) reflection. This dislocation image is thought to represent stress components of the superscrew dislocation in directions perpendicular to the c-axis.In order to investigate the origin of these stress components, steps have been carried out to determine whether the dislocation image is anisotropic in all possible reflections where g={110}. To achieve this we have excised a hexagonal prism-shaped sample from a 6H-SiC wafer, 100μm wide, polished along the six {100} crystallographic faces, such that a single micropipe ran along the axis of the sample. This enabled x-ray topographs to be taken through each of these {100} faces

Synchrotron X-Ray Topography Studies of the Propagation and Post-Growth Mutual Interaction of Threading Growth Dislocations with C-Component of Burgers Vector in PVT-Grown 4H-SiC

2012 ◽  
Vol 717-720 ◽  
pp. 343-346 ◽  
Author(s):  
Fang Zhen Wu ◽  
Huan Huan Wang ◽  
Sha Yan Byrapa ◽  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
...  
Keyword(s):  
Opposite Sign ◽  
Equilibrium Concentration ◽  
Vapor Transport ◽  
Mutual Interaction ◽  
Similar Reaction ◽  
Threading Dislocations ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
X Ray ◽  
Nucleation Sites

Synchrotron White Beam X-ray Topography (SWBXT) imaging of wafers cut parallel to the growth axis from 4H-SiC boules grown using Physical Vapor Transport has enabled visualization of the evolution of the defect microstructure. Here we present observations of the propagation and post-growth mutual interaction of threading growth dislocations with c-component of Burgers vector. Detailed contrast extinction studies reveal the presence of two types of such dislocations: pure c-axis screw dislocations and those with Burgers Vector n1c+n2a, where n1is equal to 1 and n2is equal to 1 or 2. In addition, observations of dislocation propagation show that some of the threading dislocations with c-component of Burgers adopt a curved, slightly helical morphology which can drive the dislocations from adjacent nucleation sites together enabling them to respond to the inter-dislocation forces and react. Since all of the dislocations exhibiting such helical configurations have significant screw component, and in view of the fact that such dislocations are typically not observed to glide, it is believed that such morphologies result in large part from the interaction of a non-equilibrium concentration of vacancies with the originally approximately straight dislocation cores during post-growth cooling. Such interactions can lead to complete or partial Burgers vector annihilation. Among the reactions observed are: (a) the reaction between opposite-sign threading screw dislocations with Burgers vectors c and –c wherein some segments annihilate leaving others in the form of trails of stranded loops comprising closed dislocation dipoles; (b) the reaction between threading dislocations with Burgers vectors of -c+a and c+a wherein the opposite c-components annihilate leaving behind the two a-components; (c) the similar reaction between threading dislocations with Burgers vectors of -c and c+a leaving behind the a-component.

The Formation Mechanism of Carrot Defects in SiC Epifilms

2006 ◽  
Vol 911 ◽  
Author(s):  
Hui Chen ◽  
Guan Wang ◽  
Yi Chen ◽  
Xiaoting Jia ◽  
Jie Bai ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Mechanism Of Formation ◽  
Cross Sectional ◽  
Screw Dislocations ◽  
X Ray ◽  
Transmission Electron ◽  
Sic Wafer ◽  
Scanning Electron

AbstractCarrot-like defects in a 7&#61616; off-cut (from [0001] toward <1-210> direction) 4H-SiC wafer with a 36μm thick 4H-SiC epilayer have been investigated using Nomarski optical microscopy, synchrotron white beam x-ray topography (SWBXT), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray topographs confirm that threading screw dislocations are often associated with the carrots. Cross-sectional TEM observation confirms that a prismatic stacking fault exists below the carrot. This fault was found to show contrast in all observed diffraction geometries except for g=0004. A model for the mechanism of formation of this type of defect during epitaxial growth is proposed.

scholarly journals Characterization of Screw Dislocations in a 4H-Silicon Carbide Diode Using X-Ray Microbeam Three-Dimensional Topography

2009 ◽  
Vol 615-617 ◽  
pp. 251-254 ◽  
Author(s):  
Ryohei Tanuma ◽  
Tae Tamori ◽  
Yoshiyuki Yonezawa ◽  
Hirotaka Yamaguchi ◽  
Hirofumi Matsuhata ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Strain Field ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Hollow Core ◽  
Screw Dislocations ◽  
X Ray ◽  
Microplasma Breakdown ◽  
Symmetry Break

This paper describes the study of non-hollow-core elementary screw dislocations (SDs) in silicon carbide (SiC) diodes using X-ray microbeam three-dimensional topography. Strain analysis shows that typical screw dislocations having a symmetric strain field tend to cause microplasma breakdown, whereas deformed SDs do not. The symmetry break in SDs will relax the focussing of strain and lessen the formation of defects, thereby leading to the desirable non-leak property.

High-Resolution X-ray Topography of Dislocations in 4H-SiC Epilayers

2006 ◽  
Vol 911 ◽  
Author(s):  
Isaho Kamata ◽  
Hidekazu Tsuchida ◽  
William M Vetter ◽  
Michael Dudley
Keyword(s):  
Computer Simulation ◽  
High Resolution ◽  
Grazing Incidence ◽  
Crystal Defects ◽  
Recording Media ◽  
Simulated Image ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
X Ray ◽  
Simulated Images

AbstractSilicon carbide (SiC) substrates and epilayers contain many crystal defects, such as micropipes, screw dislocations, threading edge dislocations (TEDs), basal plane dislocations (BPDs) and stacking faults. To investigate these defects, synchrotron radiation topography is frequently carried out. When the monochromatic synchrotron X-ray topography is taken by the grazing-incidence reflection geometry using 11-28 reflection, screw dislocations, TEDs and BPDs are simultaneously seen and shown as different topographic images [1]. Many studies of dislocations were reported using 11-28 reflections in 4H-SiC [1,2]. Topographic images of the dislocations have been analyzed by the ray-tracing method of computer simulation [3]. However, experimental images of dislocations were not fully matched to the fine structure of simulation images, because of a lack of resolution in recording media: conventional films and nuclear emulsion plates [3]. This time, we report obtaining high-resolution topographic images using a new recording medium, and compare results between the experiment and the computer simulation. Synchrotron topography in 11-28 reflection was carried out at SPring8 applying holography films as high-resolution recording media. The TED images are distinguished as four types, which have ribbon-like features with different rotating angles, through the use of the films. The four different TED images agree well with the computer simulated images which have been reported by Vetter et.al. taking into account of the different Burgers vector directions [3]. By comparing the three topographic images taken at g=-12-18, 11-28 and 2-1-18, we confirmed experimentally that the four types of TED images originated from the difference of Burgers vector directions. We also investigated high-resolution topographic images of elementary screw dislocations, micropipes, and BPDs in 4H-SiC epilayers. The experimental image of screw dislocation fairly matched with simulated image. The fine features in the experimental topographic images of micropipes and BPDs are also compared with the simulated images in detail. [1] T. Ohno, H. Yamaguchi, S. Kuroda, K. Kojima, T. Suzuki, K. Arai: J. cryst. Growth. Vol. 260 (2004) 209. [2] H. Tsuchida, T. Miyanagi, I. Kamata, T. Nakamura, R. Ishii, K. Nakayama and Y.Sugawara: Jpn. J. Appl. Phys. Vol. 25, (2005), L806-808. [3] W. Vetter, H. Tsuchida, I. Kamata, M. Dudley: J. Appl. Cryst. Vol. 38, (2005), 442-447.

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