Micropipe Dissociation through Thick n+ Buffer Layer Growth

2008 ◽  
Vol 600-603 ◽  
pp. 167-170
Author(s):  
Mike F. MacMillan ◽  
Edward K. Sanchez ◽  
Michael Dudley ◽  
Yi Chen ◽  
Mark J. Loboda
Keyword(s):  
Epitaxial Layer ◽  
Grazing Incidence ◽  
System Optimization ◽  
Layer Growth ◽  
Cross Sectional ◽  
Screw Dislocations ◽  
X Ray ◽  
Density Reduction ◽  
Wafer Surfaces ◽  
Koh Etching

Thick (> 25 µm) 4H n+ epitaxial layer growth was performed on 4H n+ substrates utilizing chlorine containing etch chemistries in a hot wall CVD system. Optimization of the n+ epitaxial layer growth was achieved by varying C/Si ratio and N2 flow. Desired epitaxial layers have doping levels > 5x1018 cm-3, epitaxial surface roughness <10 nm on a 20x20 µm area and overall micropipe density reduction. To confirm the conversion of micropipes into closed core screw dislocations, microscopic examination of the epitaxial and wafer surfaces was carried out after KOH etching. Grazing incidence x-ray topography (XRT) as well as cross sectional XRT and microscopy were also performed. The cross sectional evaluation showed that the dissociation of the micropipes occurs very close to the epitaxy/wafer interface.

OSTEOPOROSIS AND RISK FACTORS IN THE PATIENTS ON CHRONIC HEMODIALYSIS

2015 ◽  
pp. 50-58
Author(s):  
Thi Dung Nguyen ◽  
Tam Vo
Keyword(s):  
Quality Of Life ◽  
Risk Factors ◽  
Bone Density ◽  
Region Of Interest ◽  
Cross Sectional Study ◽  
Chronic Hemodialysis ◽  
Cross Sectional ◽  
X Ray ◽  
Density Reduction

Background: The patients on hemodialysis have a significantly decreased quality of life. One of many problems which reduce the quality of life and increase the mortality in these patients is osteoporosis and osteoporosis associated fractures. Objectives: To assess the bone density of those on hemodialysis by dual energy X ray absorptiometry and to examine the risk factors of bone density reduction in these patients. Patients and Method: This is a cross-sectional study, including 93 patients on chronic hemodialysis at the department of Hemodialysis at Cho Ray Hospital. Results: Mean bone densities at the region of interest (ROI) neck, trochanter, Ward triangle, intertrochanter and total neck are 0.603 ± 0.105; 0.583 ± 0.121; 0.811 ± 0.166; 0.489 ± 0.146; 0.723 ± 0.138 g/cm2 respectively. The prevalences of osteoporosis at those ROI are 39.8%, 15.1%; 28%; 38.7%; and 26.9% respectively. The prevalences of osteopenia at those ROI are 54.8%; 46.3%; 60.2%; 45.2% and 62.7% respectively. The prevalence of osteopososis in at least one ROI is 52.7% and the prevalence of osteopenia in at least one ROI is 47.3%. There are relations between the bone density at the neck and the gender of the patient and the albuminemia. Bone density at the trochanter is influenced by gender, albuminemia, calcemia and phosphoremia. Bone density at the intertrochanter is affected by the gender. Bone density at the Ward triangle is influenced by age and albuminemia. Total neck bone density is influenced by gender, albuminemia and phosphoremia. Conclusion: Osteoporosis in patients on chronic hemodialysis is an issue that requires our attention. There are many interventionable risk factors of bone density decrease in these patients. Key words: Osteoporosis, DEXA, chronic renal failure, chronic hemodialysis

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.

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.

Epitaxial growth and characterization of BP on Si(100) substrate for use in c-GaN study

2005 ◽  
Vol 891 ◽  
Author(s):  
Tomohiko Takeuchi ◽  
Suzuka Nishimura ◽  
Tomoyuki Sakuma ◽  
Satoru Matumoto ◽  
Kazutaka Terashima
Keyword(s):  
Epitaxial Layer ◽  
Careful Analysis ◽  
X Ray Diffraction ◽  
Si Substrate ◽  
Cross Sectional ◽  
X Ray ◽  
Si Substrates ◽  
Impurity Doping ◽  
Hall Effect Measurements

ABSTRACTBoronmonophosphide(BP) is one of the suitable materials for a buffer layer between the c-GaN(100) and Si(100) substrates. The growth of BP layer was carried out by MOCVD on Si(100) substrate of 2 inch in diameter. The growth rate was over 2 μm/h without any troubles such as the bowing or cracking. In addition, the thickness of BP epitaxial layer was uniform over a wide area. A careful analysis of x-ray diffraction suggested that the growth of BP epitaxial layer inherited the crystal orientation from Si(100) substrate. Cross-sectional TEM images showed some defects like dislocations near the interface between BP layer and Si substrate. The Hall effect measurements indicated that the conduction type of BP films grown on the both n-Si and p-Si substrates was n-type without impurity doping, and that the mobility and carrier concentrations were typically 357cm2/Vs and 1.5×1020cm−3(on n-Si) and 63cm2/Vs and 1.9×1019cm−3(on p-Si), respectively. In addition, c-GaN was grown on the substrate of BP/Si(100) by RF-MBE.

Studies of the Distribution of Elementary Threading Screw Dislocations in 4H Silicon Carbide Wafer

2008 ◽  
Vol 600-603 ◽  
pp. 301-304 ◽  
Author(s):  
Yi Chen ◽  
Ning Zhang ◽  
Xian Rong Huang ◽  
David R. Black ◽  
Michael Dudley
Keyword(s):  
Silicon Carbide ◽  
Grazing Incidence ◽  
Vapor Transport ◽  
Physical Vapor Transport ◽  
Screw Dislocations ◽  
X Ray ◽  
Pyramidal Plane

The density and sense distribution of elementary threading screw dislocations in a physical vapor transport grown 3-inch 4H silicon carbide wafer have been studied. The density of TSDs ranges between 1.6×103/cm2 and 7.1×103/cm2 and the lowest density is observed at positions approximately half radius off the wafer center. The dislocation sense of elementary threading screw dislocations can be readily revealed by the asymmetric contrast of their images in grazing-incidence x-ray topographs using pyramidal plane reflections. The circumferential and radial distributions of the sense of elementary threading screw dislocations have been studied and no clear trends are observed in either distribution.

Starting Point of Step-Bunching Defects on 4H-SiC Si-Face Substrates

2015 ◽  
Vol 821-823 ◽  
pp. 367-370 ◽  
Author(s):  
Kentaro Tamura ◽  
Masayuki Sasaki ◽  
Chiaki Kudou ◽  
Tamotsu Yamashita ◽  
Hideki Sako ◽  
...  
Keyword(s):  
Oxide Layer ◽  
Epitaxial Layer ◽  
Basal Plane ◽  
X Ray ◽  
Step Bunching ◽  
Line Feature ◽  
Starting Point ◽  
Basal Plane Dislocation ◽  
Koh Etching

On 4H-SiC Si-face substrates after H2etching, the defect with “line” feature parallel to a step as “bunched-step line” was observed. Using X-ray topography and KOH etching, we confirmed that the bunched-step line originated from basal plane dislocation (BPD). Use of the substrate with the lowest BPD density will be effective to reduce bunched-step line that would affect oxide layer reliability on an epitaxial layer. However, more detail investigation needs to classify the BPD that would become a starting point of bunched-step line.

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.

Mapping of Threading Screw Dislocations in 4H n-Type SiC Wafers

2016 ◽  
Vol 858 ◽  
pp. 376-379 ◽  
Author(s):  
Alexandre Ellison ◽  
Erik Sörman ◽  
Björn Sundqvist ◽  
Björn Magnusson ◽  
Yu Yang ◽  
...  
Keyword(s):  
Screw Dislocations ◽  
X Ray ◽  
Cvd Growth ◽  
Koh Etching

X-ray topography shows that selective KOH etching after CVD growth of n-type epilayers on highly N doped 4H SiC substrates can be used to reliably map pure and mixed Threading Screw Dislocations (TSD). The influence of the mapping grid density and the wafer position in the crystal on the average TSD density are investigated. A reliable mapping of TSD contributed to the development of 100mm SiC wafers with average TSD density down to 200 cm-2.

A New Approach to Study the Damage Induced by Inert Gases Implantation in Silicon

2005 ◽  
Vol 108-109 ◽  
pp. 357-364
Author(s):  
S. Peripolli ◽  
Marie France Beaufort ◽  
David Babonneau ◽  
Sophie Rousselet ◽  
P.F.P. Fichtner ◽  
...  
Keyword(s):  
Grazing Incidence ◽  
Inert Gases ◽  
Extended Defects ◽  
Cross Sectional ◽  
Plan View ◽  
New Approach ◽  
X Ray ◽  
Implantation Temperature ◽  
X Ray Scattering ◽  
Transmission Electron

In the present work, we report on the effects of the implantation temperature on the formation of bubbles and extended defects in Ne+-implanted Si(001) substrates. The implantations were performed at 50 keV to a fluence of 5x1016 cm-2, for distinct implantation temperatures within the 250°C≤Ti≤800°C interval. The samples are investigated using a combination of cross-sectional and plan-view Transmission Electron Microscopy (TEM) observations and Grazing Incidence Small-Angle X-ray Scattering (GISAXS)measurements. In comparison with similar He implants, we demonstrate that the Ne implants can lead to the formation of a much denser bubble system.

Grazing Incidence X-ray Topographic Studies of Threading Dislocations in Hydrothermal Grown ZnO Single Crystal Substrates

2013 ◽  
Vol 1494 ◽  
pp. 121-126 ◽  
Author(s):  
Tianyi Zhou ◽  
Balaji Raghothamachar ◽  
Fangzhen Wu ◽  
Michael Dudley
Keyword(s):  
Single Crystal ◽  
Grazing Incidence ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Screw Dislocations ◽  
X Ray ◽  
Dislocation Defects ◽  
Image Position ◽  
Threading Defects ◽  
Zno Single Crystal

ABSTRACTZnO single crystal substrates grown by the hydrothermal method have been characterized by grazing incidence X-ray topography using both monochromaticand whitesynchrotron X ray beams.11$\bar 2$4 reflection wasrecorded from the (0001) wafers and the different contrast patterns produced by different threading defects were noted. To uniquely identify the Burgers vectors of these threading dislocation defects, we use raytracingsimulation to compare with observed defect contrast. Our studies showed that threading screw dislocations are not commonly observed.Most threading edge dislocationshavetheBurgers vector of1⁄3[2$\bar 1$$\bar 1$0] or1⁄3[12$\bar 2$10]and a density of 2.88×104/cm2.

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