Do You Really Expect To Grow Epilayers On That? A Rationale For Growing Epilayers On Roughened Surfaces

2006 ◽  
Vol 911 ◽  
Author(s):  
Joseph John Sumakeris ◽  
Brett A. Hull ◽  
Michael J. O'Loughlin ◽  
S. Ha ◽  
Marek Skowronski ◽  
...  
Keyword(s):  
Basal Plane ◽  
Substrate Surface ◽  
Surface Preparation ◽  
Processing Parameters ◽  
Optimal Process ◽  
Device Structure ◽  
Process Route ◽  
Basal Plane Dislocation ◽  
Vf Drift ◽  
Edge Dislocations

AbstractWe describe surface preparation and epilayer growth techniques that readily reduce the density of Vf drift inducing basal plane dislocations in epilayers to less than 10 cm-2 and permit the fabrication of bipolar SiC devices with very good Vf stability. The optimal process route requires etching the substrate surface prior to epilayer growth to enhance the natural conversion of basal plane dislocations into threading edge dislocations during epilayer growth. The surface of this relatively rough “conversion” epilayer is subsequently repolished prior to growing the device structure. We provide details on processing parameters and potential problems as well as describe devices produced using this low basal plane dislocation growth processes.

Techniques for Minimizing the Basal Plane Dislocation Density in SiC Epilayers to Reduce Vf Drift in SiC Bipolar Power Devices

2006 ◽  
Vol 527-529 ◽  
pp. 141-146 ◽  
Author(s):  
Joseph J. Sumakeris ◽  
Peder Bergman ◽  
Mrinal K. Das ◽  
Christer Hallin ◽  
Brett A. Hull ◽  
...  
Keyword(s):  
Basal Plane ◽  
Substrate Surface ◽  
Root Cause ◽  
Voltage Instability ◽  
Selective Etch ◽  
Basal Plane Dislocation ◽  
Vf Drift ◽  
Dry Etch ◽  
Edge Dislocations ◽  
Device Size

Forward voltage instability, or Vf drift, has confounded high voltage SiC device makers for the last several years. The SiC community has recognized that the root cause of Vf drift in bipolar SiC devices is the expansion of basal plane dislocations (BPDs) into Shockley Stacking Faults (SFs) within device regions that experience conductivity modulation. In this presentation, we detail relatively simple procedures that reduce the density of Vf drift inducing BPDs in epilayers to <10 cm-2 and permit the fabrication of bipolar SiC devices with very good Vf stability. The first low BPD technique employs a selective etch of the substrate prior to epilayer growth to create a near on-axis surface where BPDs intersect the substrate surface. The second low BPD technique employs lithographic and dry etch patterning of the substrate prior to epilayer growth. Both processes impede the propagation of BPDs into epilayers by preferentially converting BPDs into threading edge dislocations (TEDs) during the initial stages of epilayer growth. With these techniques, we routinely achieve Vf stability yields of up to 90% in devices with active areas from 0.006 to 1 cm2, implying that the utility of the processes is not limited by device size.

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.

Basal Plane Dislocation Multiplication via the Hopping Frank-Read Source Mechanism and Observations of Prismatic Glide in 4H-SiC

2012 ◽  
Vol 717-720 ◽  
pp. 327-330 ◽  
Author(s):  
Huan Huan Wang ◽  
Sha Yan Byrapa ◽  
F. Wu ◽  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
...  
Keyword(s):  
Shear Stress ◽  
Slip Plane ◽  
Opposite Direction ◽  
Edge Dislocation ◽  
Basal Plane ◽  
Detailed Mechanism ◽  
Slip Planes ◽  
Basal Plane Dislocation ◽  
Edge Dislocations ◽  
Dislocation Multiplication

In this paper, we report on the synchrotron white beam topographic (SWBXT) observation of “hopping” Frank-Read sources in 4H-SiC. A detailed mechanism for this process is presented which involves threading edge dislocations experiencing a double deflection process involving overgrowth by a macrostep (MP) followed by impingement of that macrostep against a step moving in the opposite direction. These processes enable the single-ended Frank-Read sources created by the pinning of the deflected basal plane dislocation segments at the less mobile threading edge dislocation segments to “hop” from one slip plane to other parallel slip planes. We also report on the nucleation of 1/3< >{ } prismatic dislocation half-loops at the hollow cores of micropipes and their glide under thermal shear stress.

Glide of threading edge dislocations after basal plane dislocation conversion during 4H–SiC epitaxial growth

2015 ◽  
Vol 418 ◽  
pp. 7-14 ◽  
Author(s):  
Mina Abadier ◽  
Haizheng Song ◽  
Tangali S. Sudarshan ◽  
Yoosuf N. Picard ◽  
Marek Skowronski
Keyword(s):  
Epitaxial Growth ◽  
Basal Plane ◽  
Basal Plane Dislocation ◽  
Edge Dislocations

Characterization of 100 mm Diameter 4H-Silicon Carbide Crystals with Extremely Low Basal Plane Dislocation Density

2010 ◽  
Vol 645-648 ◽  
pp. 291-294 ◽  
Author(s):  
Michael Dudley ◽  
Ning Zhang ◽  
Yu Zhang ◽  
Balaji Raghothamachar ◽  
Sha Yan Byrapa ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Dislocation Density ◽  
Basal Plane ◽  
X Ray ◽  
Repetitive Process ◽  
Basal Plane Dislocation ◽  
And Behavior ◽  
New Generation ◽  
Edge Dislocations

Synchrotron White Beam X-ray Topography (SWBXT) studies are presented of basal plane dislocation (BPD) configurations and behavior in a new generation of 100mm diameter, 4H-SiC wafers with extremely low BPD densities (3-4 x 102 cm-2). The conversion of non-screw oriented, glissile BPDs into sessile threading edge dislocations (TEDs) is observed to provide pinning points for the operation of single ended Frank-Read sources. In some regions, once converted TEDs are observed to re-convert back into BPDs in a repetitive process which provides multiple BPD pinning points.

Demonstration of High Quality 4H-SiC Epitaxial Growth with Extremely Low Basal Plane Dislocation Density

2014 ◽  
Vol 778-780 ◽  
pp. 91-94 ◽  
Author(s):  
Takanori Tanaka ◽  
Naoyuki Kawabata ◽  
Yoichiro Mitani ◽  
Nobuyuki Tomita ◽  
Masayoshi Tarutani ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Basal Plane ◽  
Growth Conditions ◽  
Conversion Ratio ◽  
Lateral Growth ◽  
High Quality ◽  
Basal Plane Dislocation ◽  
Ratio Condition ◽  
High Conversion Ratio ◽  
Edge Dislocations

SiC epitaxial layer with low basal plane dislocation (BPD) density of 0.2/cm2 was successfully grown under higher C/Si ratio, which is found on the investigation about growth conditions. In order to study conversion mechanism of BPDs to threading edge dislocations (TEDs), angles between directions of BPD lines on a substrate and that of moving edges of steps ([11-2) during growth were examined. Consequently, it was revealed that almost 98% of BPDs are converted to TEDs for the case of the absolute angles above 45°. This high conversion ratio is considered to be induced by enhanced lateral growth under the higher C/Si ratio condition.

Multiplication of Basal Plane Dislocations via Interaction with c-Axis Threading Dislocations in 4H-SiC

2006 ◽  
Vol 911 ◽  
Author(s):  
Yi Chen ◽  
Govindhan Dhanaraj ◽  
Michael Dudley ◽  
Hui Zhang ◽  
Ronghui Ma ◽  
...  
Keyword(s):  
Vapor Deposition ◽  
Basal Plane ◽  
Opposite Sign ◽  
Chemical Vapor ◽  
Threading Dislocations ◽  
Dislocation Loops ◽  
X Ray ◽  
Large Numbers ◽  
Basal Plane Dislocation ◽  
Edge Dislocations

AbstractSilicon carbide (SiC) substrates with chemical vapor deposition (CVD) grown epilayers have been characterized by synchrotron white beam X-ray topography (SWBXT). Large numbers of circular basal plane dislocation loops (BPDs) were observed in the substrate which were anchored by threading screw dislocations (SDs). Threading edge dislocations (TEDs) are not observed to play an important role in the multiplication of BPDs. A SD-assisted “conservative climb” model is proposed to explain the multiplication of BPDs during growth and/or post-growth processes. BPDs are shown to multiply on adjacent parallel basal planes via single SD-assisted as well as opposite sign SD-pair-assisted “conservative climb”.

In Situ Synchrotron X-Ray Topography Observation of Double-Ended Frank-Read Sources in PVT-Grown 4H-SiC Wafers

2018 ◽  
Vol 924 ◽  
pp. 172-175 ◽  
Author(s):  
Yu Yang ◽  
Jian Qiu Guo ◽  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
Swetlana Weit ◽  
...  
Keyword(s):  
Basal Plane ◽  
Thermal Gradient ◽  
Ellipsoidal Mirror ◽  
Basal Plane Dislocation ◽  
Intricate Mechanism ◽  
Pass Through ◽  
Dislocation Sources ◽  
Edge Dislocations ◽  
Sic Wafer

We present in-situ observations of the dynamical operation of multiple double-ended Frank-Read dislocation sources in a PVT-grown 4H-SiC wafer under thermal gradient stresses. The nucleation of these sources is facilitated by a specific configuration consisting of one basal plane dislocation (BPD) segment pinned by two threading edge dislocations (TEDs). This configuration is formed during PVT crystal growth by deflection of TEDs on to the basal planes by macrosteps and re-deflection of resulting BPDs back into TEDs. Under the influence of thermal gradient stresses induced by heating inside a double ellipsoidal mirror furnace, the pinned BPD segment glides and activates dislocation multiplication by the double Frank-Read source mechanism. A more intricate mechanism of swapping of TED pinning points between Frank-Read sources lying on same basal plane is identified, enabling one dislocation loop to effectively “pass through” the other dislocations on same basal plane.

Conversion of Basal Plane Dislocations to Threading Edge Dislocations in Growth of Epitaxial Layers on 4H-SiC Substrates with a Vicinal Off-Angle

2014 ◽  
Vol 778-780 ◽  
pp. 99-102 ◽  
Author(s):  
Keiko Masumoto ◽  
Sachiko Ito ◽  
Hideto Goto ◽  
Hirotaka Yamaguchi ◽  
Kentaro Tamura ◽  
...  
Keyword(s):  
Epitaxial Growth ◽  
Edge Dislocation ◽  
Basal Plane ◽  
Conversion Ratio ◽  
Epitaxial Layers ◽  
Etch Pits ◽  
X Ray ◽  
Basal Plane Dislocation ◽  
Edge Dislocations ◽  
Koh Etching

We have investigated a conversion of basal plane dislocation (BPD) to threading edge dislocation (TED) in growth of epitaxial layers (epi-layers) on 4H-SiC vicinal substrates with an off-angle of 0.85° at low C/Si ratio of 0.7 by using deep KOH etching and X-ray topography observations. Deep KOH etching indicated that BPDs in the substrates converted to TEDs in the epi-layers. X-ray topography observations suggested that the conversion occurred during epitaxial growth when the thickness of epi-layers was less than 1.5 μm. We found that the conversion ratio obtained from counting deep KOH etch pits was over 99%.

Growth of Low Basal Plane Dislocation Density SiC Epitaxial Layers

2006 ◽  
Vol 527-529 ◽  
pp. 243-246 ◽  
Author(s):  
Ze Hong Zhang ◽  
Tangali S. Sudarshan
Keyword(s):  
Dislocation Density ◽  
Epitaxial Growth ◽  
Basal Plane ◽  
Voltage Drop ◽  
Etch Pits ◽  
Forward Voltage ◽  
Pin Diodes ◽  
Forward Voltage Drop ◽  
Basal Plane Dislocation ◽  
Edge Dislocations

A method was developed in our laboratory to grow low basal plane dislocation (BPD) density and BPD-free SiC epilayers. The key approach is to subject the SiC substrates to defect preferential etching, followed by conventional epitaxial growth. It was found that the creation of BPD etch pits on the substrates can greatly enhance the conversion of BPDs to threading edge dislocations (TEDs) during epitaxy, and thus low BPD density and BPD-free SiC epilayers are obtained. The reason why BPD etch pits can promote the above conversion is discussed. The SiC epilayer growth by this method is very promising in overcoming forward voltage drop degradation of SiC PiN diodes.

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