Page 1. Self-heating of 4H-SiC PiN Diodes at High Current Densities Michael E. Levinshtein 1,a , ... more Page 1. Self-heating of 4H-SiC PiN Diodes at High Current Densities Michael E. Levinshtein 1,a , Tigran T. Mnatsakanov 2,b , Pavel A. Ivanov 1,c , John W. Palmour 3,d , Mrinal K. Das 3,e , and Brett A. Hull 3,f 1Ioffe Institute of RAS, 26 Politekhnicheskaya, 194021 St. ...
ABSTRACT Silicon carbide (SiC) materials technology has made rapid advances in recent years. Whil... more ABSTRACT Silicon carbide (SiC) materials technology has made rapid advances in recent years. While increasing the wafer diameter from 75 mm to 100 mm, the substrate quality has been greatly improved with much reduced defect density, resulting in higher device yields. Cree is poised to increase the wafer diameter to 150 mm in 2012, which will further reduce the cost of SiC devices. SiC Schottky diodes have demonstrated very high reliability in the field and are being extensively used in Switch Mode Power Supplies (SMPS), and solar inverters, and other applications. Cree has also commercially released a 1200 V, 20 A SiC MOSFET which has been used in solar inverter along with SiC Schottky diode to provide an efficiency gain of 2.36%. More recent R&D results at Cree indicate that the on-resistance of the MOSFET can be reduced by 2x, which will further improve performance and reduce cost.
In this paper, a comparative study of 1200V Silicon IGBTs with Silicon Carbide (SiC) MOSFETs is p... more In this paper, a comparative study of 1200V Silicon IGBTs with Silicon Carbide (SiC) MOSFETs is presented for a 6kVA single-phase 230V online Uninterruptible Power Supply (UPS) system. The UPS is first tested with the 1200V silicon IGBT/Diode devices (2 parallel 34A IGBT/diode) and then the inverter devices are replaced by next generation SiC 1200V MOSFET/Diode devices (2 parallel 20A
Page 1. High Current 6 kV 4H-SiC PiN Diodes for Power Module Switching Applications Brett A. Hull... more Page 1. High Current 6 kV 4H-SiC PiN Diodes for Power Module Switching Applications Brett A. Hull 1,a , Mrinal K. Das 1 , James T. Richmond 1 , Bradley Heath 1 , Joseph J. Sumakeris 1 , Bruce Geil 2 , and Charles J. Scozzie 2 ...
TDDB measurements of NMOS capacitor fabricated with 1200°C dry oxide with 1300°C N2O anneal were ... more TDDB measurements of NMOS capacitor fabricated with 1200°C dry oxide with 1300°C N2O anneal were performed at 175°C and 300°C under high positive bias stress. The devices are biased into strong accumulation mode such that the field in the oxide is high enough to collect breakdown data in a reasonable period of time. We observe that at 175°C, a 100-year Mean Time to Failure (MTTF) is obtained at an electric field of 3 MV/cm in the oxide. The TDDB measurement has also been performed at 300°C where lifetime has been reduced by a few orders of magnitude, but with an acceptable 100-year MTTF. Recent reliability results on similarly oxidized MOSFETs have shown failures along the same trend as the n-type capacitors, indicating that MOSFETs and MOS capacitors can have similar reliability despite inherent processing and structural differences. PMOS capacitors fabricated with the aforementioned dry + N2O process as well as capacitors fabricated using the low DIT nitridation techniques show ac...
ABSTRACTSingle crystal SiC is a wide band-gap semiconductor with material characteristics that ma... more ABSTRACTSingle crystal SiC is a wide band-gap semiconductor with material characteristics that make it quite suitable for high voltage and high current applications. However, these devices are currently limited by their passivation. Significant improvements have been made with oxides on SiC. The most notable oxide processes are the re-oxidation anneal, a stacked ONO dielectric, and nitridation using an NO or N2O anneal. Additional improvements in lateral MOSFET mobility have been achieved using a surface channel implant, and lower temperature implant activation anneals. However, the passivation remains a significant limitation for SiC power devices.
Metabolic profiling of biofluids from tuberculosis (TB) patients would help us in understanding t... more Metabolic profiling of biofluids from tuberculosis (TB) patients would help us in understanding the disease pathophysiology and may also be useful for the development of novel diagnostics and host-directed therapy. In this pilot study we have compared the urine metabolic profiles of two groups of subjects having similar TB symptoms and categorized as active TB (ATB, n = 21) and non-TB (NTB, n = 21) based on GeneXpert test results. Silylation, gas chromatography mass spectrometry, and standard chemometric methods were employed to identify the important molecules and deregulated metabolic pathways. Eleven active TB patients were followed up on longitudinally for comparative urine metabolic profiling with healthy controls (n = 11). A set of 42 features qualified to have a variable importance parameter score of > 1.5 of a partial least-squares discriminate analysis model and fold change of > 1.5 at p value < 0.05 between ATB and NTB. Using these variables, a receiver operating characteristics curve was plotted and the area under the curve was calculated to be 0.85 (95% CI: 0.72-0.96). Several of these variables that represent norepinephrine, gentisic acid, 4-hydroxybenzoic acid, hydroquinone, and 4-hydroxyhippuric acid are part of the tyrosine-phenylalanine metabolic pathway. In the longitudinal study we observed a treatment-dependent trend in the urine metabolome of follow-up samples, and subjects declared as clinically cured showed similar metabolic profile as those of asymptomatic healthy subjects. The deregulated tyrosine-phenylalanine axis reveals a potential target for diagnostics and intervention in TB.
2008 20th International Symposium on Power Semiconductor Devices and IC's, 2008
Abstract Rapidly improving 4H-SiC material quality and a maturing MOS process/design have enable... more Abstract Rapidly improving 4H-SiC material quality and a maturing MOS process/design have enabled the development of the largest 10 kV MOSFET to date and the first 10 kV n-IGBT capable of flowing 10 A and 4 A, respectively, with very low on-resistances. With 20V on the gate, ...
2007 International Semiconductor Device Research Symposium, 2007
The commercial production of 1200 V 4H-SiC power MOSFETs is quickly becoming feasible in light of... more The commercial production of 1200 V 4H-SiC power MOSFETs is quickly becoming feasible in light of advances made in 4H-SiC substrate quality, improvements made in epitaxy, investigations of optimum device deign, advances made in increasing channel mobility with nitridation annealing, and optimization of device fabrication processes. These devices promise to enhance the efficiency of power handling circuits that currently rely
Page 1. Improved 4H-SiC MOS Interfaces Produced via Two Independent Processes: Metal Enhanced Oxi... more Page 1. Improved 4H-SiC MOS Interfaces Produced via Two Independent Processes: Metal Enhanced Oxidation and 1300 o C NO Anneal Mrinal K. Das 1a , Brett A. Hull 1 , Sumi Krishnaswami 1 , Fatima Husna 1 , Sarah Haney ...
Forward voltage instability, or Vf drift, has confounded high voltage SiC device makers for the l... more 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) ...
Page 1. Self-heating of 4H-SiC PiN Diodes at High Current Densities Michael E. Levinshtein 1,a , ... more Page 1. Self-heating of 4H-SiC PiN Diodes at High Current Densities Michael E. Levinshtein 1,a , Tigran T. Mnatsakanov 2,b , Pavel A. Ivanov 1,c , John W. Palmour 3,d , Mrinal K. Das 3,e , and Brett A. Hull 3,f 1Ioffe Institute of RAS, 26 Politekhnicheskaya, 194021 St. ...
ABSTRACT Silicon carbide (SiC) materials technology has made rapid advances in recent years. Whil... more ABSTRACT Silicon carbide (SiC) materials technology has made rapid advances in recent years. While increasing the wafer diameter from 75 mm to 100 mm, the substrate quality has been greatly improved with much reduced defect density, resulting in higher device yields. Cree is poised to increase the wafer diameter to 150 mm in 2012, which will further reduce the cost of SiC devices. SiC Schottky diodes have demonstrated very high reliability in the field and are being extensively used in Switch Mode Power Supplies (SMPS), and solar inverters, and other applications. Cree has also commercially released a 1200 V, 20 A SiC MOSFET which has been used in solar inverter along with SiC Schottky diode to provide an efficiency gain of 2.36%. More recent R&amp;D results at Cree indicate that the on-resistance of the MOSFET can be reduced by 2x, which will further improve performance and reduce cost.
In this paper, a comparative study of 1200V Silicon IGBTs with Silicon Carbide (SiC) MOSFETs is p... more In this paper, a comparative study of 1200V Silicon IGBTs with Silicon Carbide (SiC) MOSFETs is presented for a 6kVA single-phase 230V online Uninterruptible Power Supply (UPS) system. The UPS is first tested with the 1200V silicon IGBT/Diode devices (2 parallel 34A IGBT/diode) and then the inverter devices are replaced by next generation SiC 1200V MOSFET/Diode devices (2 parallel 20A
Page 1. High Current 6 kV 4H-SiC PiN Diodes for Power Module Switching Applications Brett A. Hull... more Page 1. High Current 6 kV 4H-SiC PiN Diodes for Power Module Switching Applications Brett A. Hull 1,a , Mrinal K. Das 1 , James T. Richmond 1 , Bradley Heath 1 , Joseph J. Sumakeris 1 , Bruce Geil 2 , and Charles J. Scozzie 2 ...
TDDB measurements of NMOS capacitor fabricated with 1200°C dry oxide with 1300°C N2O anneal were ... more TDDB measurements of NMOS capacitor fabricated with 1200°C dry oxide with 1300°C N2O anneal were performed at 175°C and 300°C under high positive bias stress. The devices are biased into strong accumulation mode such that the field in the oxide is high enough to collect breakdown data in a reasonable period of time. We observe that at 175°C, a 100-year Mean Time to Failure (MTTF) is obtained at an electric field of 3 MV/cm in the oxide. The TDDB measurement has also been performed at 300°C where lifetime has been reduced by a few orders of magnitude, but with an acceptable 100-year MTTF. Recent reliability results on similarly oxidized MOSFETs have shown failures along the same trend as the n-type capacitors, indicating that MOSFETs and MOS capacitors can have similar reliability despite inherent processing and structural differences. PMOS capacitors fabricated with the aforementioned dry + N2O process as well as capacitors fabricated using the low DIT nitridation techniques show ac...
ABSTRACTSingle crystal SiC is a wide band-gap semiconductor with material characteristics that ma... more ABSTRACTSingle crystal SiC is a wide band-gap semiconductor with material characteristics that make it quite suitable for high voltage and high current applications. However, these devices are currently limited by their passivation. Significant improvements have been made with oxides on SiC. The most notable oxide processes are the re-oxidation anneal, a stacked ONO dielectric, and nitridation using an NO or N2O anneal. Additional improvements in lateral MOSFET mobility have been achieved using a surface channel implant, and lower temperature implant activation anneals. However, the passivation remains a significant limitation for SiC power devices.
Metabolic profiling of biofluids from tuberculosis (TB) patients would help us in understanding t... more Metabolic profiling of biofluids from tuberculosis (TB) patients would help us in understanding the disease pathophysiology and may also be useful for the development of novel diagnostics and host-directed therapy. In this pilot study we have compared the urine metabolic profiles of two groups of subjects having similar TB symptoms and categorized as active TB (ATB, n = 21) and non-TB (NTB, n = 21) based on GeneXpert test results. Silylation, gas chromatography mass spectrometry, and standard chemometric methods were employed to identify the important molecules and deregulated metabolic pathways. Eleven active TB patients were followed up on longitudinally for comparative urine metabolic profiling with healthy controls (n = 11). A set of 42 features qualified to have a variable importance parameter score of &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 1.5 of a partial least-squares discriminate analysis model and fold change of &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 1.5 at p value &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05 between ATB and NTB. Using these variables, a receiver operating characteristics curve was plotted and the area under the curve was calculated to be 0.85 (95% CI: 0.72-0.96). Several of these variables that represent norepinephrine, gentisic acid, 4-hydroxybenzoic acid, hydroquinone, and 4-hydroxyhippuric acid are part of the tyrosine-phenylalanine metabolic pathway. In the longitudinal study we observed a treatment-dependent trend in the urine metabolome of follow-up samples, and subjects declared as clinically cured showed similar metabolic profile as those of asymptomatic healthy subjects. The deregulated tyrosine-phenylalanine axis reveals a potential target for diagnostics and intervention in TB.
2008 20th International Symposium on Power Semiconductor Devices and IC's, 2008
Abstract Rapidly improving 4H-SiC material quality and a maturing MOS process/design have enable... more Abstract Rapidly improving 4H-SiC material quality and a maturing MOS process/design have enabled the development of the largest 10 kV MOSFET to date and the first 10 kV n-IGBT capable of flowing 10 A and 4 A, respectively, with very low on-resistances. With 20V on the gate, ...
2007 International Semiconductor Device Research Symposium, 2007
The commercial production of 1200 V 4H-SiC power MOSFETs is quickly becoming feasible in light of... more The commercial production of 1200 V 4H-SiC power MOSFETs is quickly becoming feasible in light of advances made in 4H-SiC substrate quality, improvements made in epitaxy, investigations of optimum device deign, advances made in increasing channel mobility with nitridation annealing, and optimization of device fabrication processes. These devices promise to enhance the efficiency of power handling circuits that currently rely
Page 1. Improved 4H-SiC MOS Interfaces Produced via Two Independent Processes: Metal Enhanced Oxi... more Page 1. Improved 4H-SiC MOS Interfaces Produced via Two Independent Processes: Metal Enhanced Oxidation and 1300 o C NO Anneal Mrinal K. Das 1a , Brett A. Hull 1 , Sumi Krishnaswami 1 , Fatima Husna 1 , Sarah Haney ...
Forward voltage instability, or Vf drift, has confounded high voltage SiC device makers for the l... more 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) ...
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