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 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.

Large-Area Mapping of Dislocations in 4H-SiC from Carbon-Face (000-1) by Using Vaporized KOH Etching near 1000 °C

2013 ◽  
Vol 740-742 ◽  
pp. 829-832
Author(s):  
Yong Zhao Yao ◽  
Yukari Ishikawa ◽  
Koji Sato ◽  
Yoshihiro Sugawara ◽  
Katsunori Danno ◽  
...  
Keyword(s):  
Basal Plane ◽  
Chemical Etching ◽  
Sample Thickness ◽  
Large Area ◽  
Inexpensive Method ◽  
Etching Technique ◽  
Screw Dislocations ◽  
Wafer Thickness ◽  
Edge Dislocations ◽  
Koh Etching

To solve the problem that no preferential chemical etching is available for dislocation revelation from the carbon-face (C-face) of 4H-SiC, a novel etching technique using vaporized KOH has been developed. It was found that this etching technique can reveal the three commonly found dislocation types, i.e., threading screw dislocations (TSDs), threading edge dislocations (TEDs) and basal plane dislocations (BPDs) as large hexagonal, small hexagonal and triangular, respectively. Centimeter-scale dislocation mapping has been obtained, and the pit positions on the C-face were compared with those on the Si-face, to study the dislocation propagation behaviors across the sample thickness. We have found one-to-one correlation for nearly 96% of the TSDs, indicating a dominant proportion of TSDs penetrate the whole wafer thickness. The vaporized KOH etching technique has provided an effective and inexpensive method of making inch-scale mapping of dislocation distribution for the C-face epitaxial and bulky 4H-SiC.

Dislocation Revelation in Highly Doped N-Type 4H-SiC by Molten KOH Etching with Na2O2 Additive

2011 ◽  
Vol 679-680 ◽  
pp. 290-293 ◽  
Author(s):  
Yong Zhao Yao ◽  
Yukari Ishikawa ◽  
Yoshihiro Sugawara ◽  
Hiroaki Saitoh ◽  
Katsunori Danno ◽  
...  
Keyword(s):  
Electron Concentration ◽  
Basal Plane ◽  
Wet Etching ◽  
Etch Pits ◽  
Screw Dislocations ◽  
Edge Dislocations ◽  
Koh Etching

We have proposed a new wet etching recipe using molten KOH and Na2O2 as the etchant (“KN etching”) for dislocation revelation in highly doped n-type 4H-SiC (n+-4H-SiC). Threading screw dislocations (TSDs) and threading edge dislocations (TEDs) have been clearly revealed as hexagonal etch pits differing in pit sizes, and basal plane dislocations (BPDs) as seashell-shaped pits. This new etching recipe has provided a solution to the problem that conventional KOH etching is not effective for dislocation identification in 4H-SiC if the electron concentration is high (>mid-1018 cm-3). We have investigated the effect of SiC off-cut angle on KN etching and it has been shown that the “KN etching” is applicable for the n+-SiC substrate with off-angle from 0o to 8o.

New Separation Method of Threading Dislocations in 4H-SiC Epitaxial Layer by Molten KOH Etching

2011 ◽  
Vol 679-680 ◽  
pp. 298-301 ◽  
Author(s):  
T. Katsuno ◽  
Y. Watanabe ◽  
Fujiwara Hirokazu ◽  
Masaki Konishi ◽  
Takeo Yamamoto ◽  
...  
Keyword(s):  
Epitaxial Layer ◽  
Basal Plane ◽  
Separation Method ◽  
New Method ◽  
Threading Dislocations ◽  
Screw Dislocations ◽  
Etch Pit ◽  
Almost All ◽  
Edge Dislocations ◽  
Koh Etching

A new method for the separation of threading screw dislocations (TSD) and threading edge dislocations (TED) in a 4H-SiC epitaxial layer is proposed by measurement of the etch pit angles. The etch pit angles of the TSDs and TEDs were 28±3 and 18±3°, respectively. In the case of etch pit depths within the epitaxial layer, the values were almost constant. Almost all of the TSDs were converted from basal plane dislocations (BPDs) at the epitaxial layer/substrate interface.

Investigation of Low Angle Grain Boundaries in Hexagonal Silicon Carbide

2006 ◽  
Vol 955 ◽  
Author(s):  
Yi Chen ◽  
Hui Chen ◽  
Ning Zhang ◽  
Michael Dudley ◽  
Ronghui Ma
Keyword(s):  
Silicon Carbide ◽  
Grain Boundaries ◽  
Basal Plane ◽  
Vapor Transport ◽  
Threading Dislocations ◽  
Prismatic Plane ◽  
Screw Dislocations ◽  
X Ray ◽  
Edge Dislocations ◽  
Dislocation Walls

ABSTRACTInteraction between basal plane dislocations and single or well-spaced threading dislocations is discussed based on synchrotron white beam X-ray topographic studies carried out on physical vapor transport grown hexagonal silicon carbide single crystals. The basal plane dislocations are able to cut through single or well-spaced threading edge dislocations even if the formation of kinks/jogs is energetically unfavorable while threading screw dislocations were mostly observed to act as effective pinning points. However, basal plane dislocations can sometimes cut through a threading screw dislocation, forming a superjog and which subsequently migrates on the prismatic plane via a cross-slip process. Threading edge dislocation walls act as obstacles for the glide of basal plane dislocations and the mechanism by which this occurs is discussed. The character of low angle grain boundaries and their dislocation content are discussed.

Dislocations Propagation Study Trough High-Resolution 4H-SiC Substrate Mapping

2019 ◽  
Vol 963 ◽  
pp. 276-279 ◽  
Author(s):  
Ruggero Anzalone ◽  
Nicolò Piluso ◽  
Andrea Severino ◽  
Simona Lorenti ◽  
Giuseppe Arena ◽  
...  
Keyword(s):  
High Resolution ◽  
Epitaxial Layer ◽  
Basal Plane ◽  
Stacking Faults ◽  
Screw Dislocations ◽  
Density Maps ◽  
Dislocations Density ◽  
Koh Etching

In this work a deep investigation of the dislocation on 4H-SiC substrate has been shown. The dislocation intersecting the surface were enhanced by KOH etching at 500 deg. C. performed on whole 6 inches substrate. A comparison between basal plane dislocations and threading screw dislocations in the substrate with the defects in the epitaxial layer (mainly stacking faults and carrots) was performed. The comparison between shows a correlation between basal plane dislocations density and stacking faults density maps.

Characterization of Basal Plane Dislocations in 4H-SiC Substrates by Topography Analysis of Threading Edge Dislocations in Epilayers

2010 ◽  
Vol 645-648 ◽  
pp. 303-306 ◽  
Author(s):  
Isaho Kamata ◽  
Masahiro Nagano ◽  
Hidekazu Tsuchida
Keyword(s):  
High Resolution ◽  
Epitaxial Layer ◽  
Basal Plane ◽  
Grazing Incidence ◽  
Size Difference ◽  
Etch Pits ◽  
Burgers Vector ◽  
Vector Direction ◽  
Edge Dislocations

Burgers vector directions of threading edge dislocations (TEDs) in 4H-SiC epitaxial layer are distinguished by grazing incidence high resolution topography. Based on comparison between appearance of KOH etch pits and direction of TED Burgers vector, the size difference of the TED etch pits is found to be dependent on their Burgers vector directions. Examining TEDs in the epilayer by topography, the Burgers vector direction of basal plane dislocations (BPDs) in the substrate is identified. Correspondence between the topography contrast and the sense of a BPD is also investigated.

Nucleation of c-Axis Screw Dislocations at Substrate Surface Damage during 4H-Silicon Carbide Homo-Epitaxy

2010 ◽  
Vol 645-648 ◽  
pp. 295-298 ◽  
Author(s):  
Michael Dudley ◽  
Ning Zhang ◽  
Yu Zhang ◽  
Balaji Raghothamachar ◽  
Edward K. Sanchez
Keyword(s):  
Basal Plane ◽  
Opposite Sign ◽  
Substrate Surface ◽  
Surface Damage ◽  
Dislocation Nucleation ◽  
Screw Dislocations ◽  
Basal Plane Dislocation ◽  
Residual Damage ◽  
Step Flow Growth ◽  
Edge Dislocations

Observations of dislocation nucleation occurring at substrate surface scratches during 4H-SiC CVD homoepitaxial growth are reported. Sub-surface residual damage associated with the scratches is observed to act as nucleation sites for basal plane dislocations (BPDs), threading edge dislocations (TEDs) and threading screw dislocations (TSDs) in the epilayer. TEDs and BPDs replicate from the surface intersections of basal plane dislocation half-loops injected into the substrate surface. A model for the nucleation mechanism of TSDs, which nucleate in opposite sign pairs, is presented which involves overgrowth of surface indentations associated with the scratch during step flow growth. Atomic steps which approach these local surface indentations can collapse creating pairs of opposite sign screw dislocations which have Burgers vector magnitude equal to the magnitude of the step disregistry created during the collapse.

Behavior of Basal Plane Dislocations and Low Angle Grain Boundary Formation in Hexagonal Silicon Carbide

2007 ◽  
Vol 556-557 ◽  
pp. 231-234 ◽  
Author(s):  
Yi Chen ◽  
Govindhan Dhanaraj ◽  
William M. Vetter ◽  
Rong Hui Ma ◽  
Michael Dudley
Keyword(s):  
Silicon Carbide ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Basal Plane ◽  
Opposite Sign ◽  
Three Dimensional ◽  
Cross Slip ◽  
X Ray ◽  
Tilt Boundaries ◽  
Edge Dislocations

The interactions between basal plane dislocations (BPDs) and threading screw and edge dislocations (TSDs and TEDs) in hexagonal SiC have been studied using synchrotron white beam x-ray topography (SWBXT). TSDs are shown to strongly interact with advancing basal plane dislocations (BPDs) while TEDs do not. A BPD can cut through an individual TED without the formation of jogs or kinks. The BPDs were observed to be pinned by TSDs creating trailing dislocation dipoles. If these dipoles are in screw orientation segments can cross-slip and annihilate also potentially leaving isolated trailing loops. The three-dimensional (3D) distribution of BPDs can lead to aggregation of opposite sign edge segments leading to the creation of low angle grain boundaries (LAGBs) characterized by pure basal plane tilt of magnitude determined by the net difference in densities of the opposite sign dislocations. Similar aggregation can also occur against pre-existing prismatic tilt boundaries made up of TED walls with the net difference in densities of the opposite sign dislocations contributing some basal plane tilt character to the LAGB.

Characterization and Reduction of Defects in 4H-SiC Substrate and Homo-Epitaxial Wafer

2020 ◽  
Vol 1004 ◽  
pp. 387-392 ◽  
Author(s):  
Long Yang ◽  
Li Xia Zhao ◽  
Hui Wang Wu ◽  
Yafei Liu ◽  
Tuerxun Ailihumaer ◽  
...  
Keyword(s):  
Basal Plane ◽  
Chemical Vapor ◽  
Vapor Transport ◽  
Etching Time ◽  
X Ray ◽  
Half Loop ◽  
Dislocation Behavior ◽  
Edge Dislocations ◽  
Defect Morphology ◽  
Koh Etching

4H-SiC substrates and homo-epitaxial layers were obtained using the traditional methods of physical vapor transport and chemical vapor deposition. Defect morphology has been studied using both Synchrotron White Beam X-ray Topography and Monochromatic Beam X-ray Topography. Molten KOH etching method was adopted to further investigate the dislocation behavior mechanisms. Deflected dislocations were observed at the periphery regions in both substrate and epitaxial wafers. 3C polytypes and half loop arrays were observed in the 4H-SiC epitaxial wafer. It is also found that the majority of basal plane dislocations are converted to threading edge dislocations in the epitaxial wafer samples. The proportion of BPD to TED conversion depends on the surface step morphology and growth mode in epitaxial growth which in turn depends on the C/Si ratio. By the optimization of etching time prior to epitaxy and C/Si ratio, high-quality epitaxial wafers with extremely low basal plane dislocations densities (＜0.1 cm-2) was obtained.

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