Correlation between Inversion Channel Mobility and Interface Traps near the Conduction Band in SiC MOSFETs

Current power MOSFET devices on Silicon Carbide show a limited inversion channel mobility, which can be a result of the expected very high density of interface states near the conduction band . In the current work, the effect of the post implantation annealing temperature, the thermal oxidation and the nitrogen doping of the n-epi layer on the density of these interface traps is investigated using capacity-conductance measurements. Instead of the usage of very high frequencies as used in , in this investigation the measurements were performed in liquid nitrogen to decrease the recharging times of the interface traps.Due to the different processing the samples showed a wide spreading of the inversion channel mobility. The conductance measurements show a characteristic peak caused by the conduction band near interface traps especially for the low temperature measurements. But these traps could not be correlated to the mobility. Instead, a correlation to the nitrogen doping of the epi layer could be observed.

Download Full-text

SiC MOSFET Channel Mobility Dependence on Substrate Doping and Temperature Considering High Density of Interface Traps

Materials Science Forum ◽

10.4028/www.scientific.net/msf.556-557.835 ◽

2007 ◽

Vol 556-557 ◽

pp. 835-838 ◽

Cited By ~ 3

Author(s):

Amador Pérez-Tomás ◽

Michael R. Jennings ◽

Philip A. Mawby ◽

James A. Covington ◽

Phillippe Godignon ◽

...

Keyword(s):

Degradation Mechanism ◽

Mobility Model ◽

Effect Of Temperature ◽

Coulomb Scattering ◽

Interface Traps ◽

Channel Mobility ◽

Inversion Channel ◽

Scattering Effects ◽

Charge Concentration ◽

Substrate Doping

In prior work we have proposed a mobility model for describing the mobility degradation observed in SiC MOSFET devices, suitable for being implemented into a commercial simulator, including Coulomb scattering effects at interface traps. In this paper, the effect of temperature and doping on the channel mobility has been modelled. The computation results suggest that the Coulomb scattering at charged interface traps is the dominant degradation mechanism. Simulations also show that a temperature increase implies an improvement in field-effect mobility since the inversion channel concentration increases and the trapped charge is reduced due to bandgap narrowing. In contrast, increasing the substrate impurity concentration further degrades the fieldeffect mobility since the inversion charge concentration decreases for a given gate bias. We have good agreement between the computational results and experimental mobility measurements.

Download Full-text

The Effects of Post-Oxidation Anneal Conditions on Interface State Density Near the Conduction Band Edge and Inversion Channel Mobility for SiC MOSFETs

MRS Proceedings ◽

10.1557/proc-622-t8.7.1 ◽

2000 ◽

Vol 622 ◽

Cited By ~ 1

Author(s):

G.Y. Chung ◽

C.C. Tin ◽

J. R. Williams ◽

K. McDonald ◽

M. Di Ventra ◽

...

Keyword(s):

Nitric Oxide ◽

Conduction Band ◽

Interface State ◽

Interface States ◽

State Density ◽

Interface State Density ◽

Band Edge ◽

Conduction Band Edge ◽

Channel Mobility ◽

Inversion Channel

ABSTRACTResults are reported for the passivation of interface states near the conduction band edge in n-4H-SiC using post-oxidation anneals in nitric oxide, ammonia and forming gas (N2/5%H2). Anneals in nitric oxide and ammonia reduce the interface state density significantly, while forming gas anneals are largely ineffective. Results suggest that interface states in SiO2/SiC and SiO2/Si have different origins, and a model is described for interface state passivation by nitrogen in the SiO2/SiC system. The inversion channel mobility of 4H-SiC MOSFETs increases with the NO annealing.

Download Full-text

Sodium Enhanced Oxidation of Si-Face 4H-SiC: A Method to Remove Near Interface Traps

Materials Science Forum ◽

10.4028/www.scientific.net/msf.556-557.487 ◽

2007 ◽

Vol 556-557 ◽

pp. 487-492 ◽

Cited By ~ 14

Author(s):

Einar Ö. Sveinbjörnsson ◽

Fredrik Allerstam ◽

H.Ö. Ólafsson ◽

G. Gudjónsson ◽

D. Dochev ◽

...

Keyword(s):

Field Effect ◽

Field Effect Transistors ◽

Energy Levels ◽

Metal Oxide Semiconductor ◽

Oxide Semiconductor ◽

Conduction Band Edge ◽

Interface Traps ◽

Channel Mobility ◽

Inversion Channel ◽

Enhanced Oxidation

We demonstrate how sodium enhanced oxidation of Si face 4H-SiC results in removal of near-interface traps at the SiO2/4H-SiC interface. These detrimental traps have energy levels close to the SiC conduction band edge and are responsible for low electron inversion channel mobilities (1-10 cm2/Vs) in Si face 4H-SiC metal-oxide-semiconductor field effect transistors. The presence of sodium during oxidation increases the oxidation rate and suppresses formation of these nearinterface traps resulting in high inversion channel mobility of 150 cm2/Vs in such transistors. Sodium can be incorporated by using carrier boats made of sintered alumina during oxidation or by deliberate sodium contamination of the oxide during formation of the SiC/SiO2 interface.

Download Full-text

Improved Inversion Channel Mobility in Si-face 4H-SiC MOSFETs by Phosphorus Incorporation Technique

MRS Proceedings ◽

10.1557/proc-1246-b06-06 ◽

2010 ◽

Vol 1246 ◽

Cited By ~ 6

Author(s):

Dai Okamoto ◽

Hiroshi Yano ◽

Shinya Kotake ◽

Kenji Hirata ◽

Tomoaki Hatayama ◽

...

Keyword(s):

Conduction Band ◽

Field Effect ◽

Field Effect Transistors ◽

Interface State ◽

State Density ◽

Interface State Density ◽

Band Edge ◽

Conduction Band Edge ◽

Channel Mobility ◽

Inversion Channel

AbstractWe propose a new technique to fabricate 4H-SiC metal–oxide–semiconductor field-effect transistors (MOSFETs) with high inversion channel mobility. P atoms were incorporated into the SiO2/4H-SiC(0001) interface by post-oxidation annealing using phosphoryl chloride (POCl3). The interface state density at 0.2 eV from the conduction band edge was reduced to less than 1 × 1011 cm−2eV−1 by the POCl3 annealing at 1000 °C. The peak field-effect mobility of 4H-SiC MOSFETs on (0001) Si-face processed with POCl3 annealing at 1000 °C was approximately 90 cm2/Vs. The high channel mobility is attributed to the reduced interface state density near the conduction band edge.

Download Full-text

Passivation and Depassivation of Interface Traps at the SiO2/4H-SiC Interface by Potassium Ions

Materials Science Forum ◽

10.4028/www.scientific.net/msf.717-720.761 ◽

2012 ◽

Vol 717-720 ◽

pp. 761-764 ◽

Cited By ~ 2

Author(s):

Pétur Gordon Hermannsson ◽

Einar Ö. Sveinbjörnsson

Keyword(s):

Thermal Stability ◽

Conduction Band ◽

Energy Levels ◽

Sample Surface ◽

Conduction Band Edge ◽

Potassium Ions ◽

Interface Traps ◽

Bias Stress ◽

Dry Oxidation ◽

Thermal Stability Of

We investigate the passivation of interface traps by method of oxidizing Si-face 4H-SiC in the presence of potassium as well as examining the thermal stability of this passivation process. It is observed that this type of dry oxidation leads to a strong passivation of interface traps at the SiO2/4H-SiC interface with energy levels near the SiC conduction band edge. Furthermore, it is observed that if potassium ions residing at the SiO2/SiC interface are moved towards the sample surface by exposing them to ultraviolet light (UV) under an applied depletion bias stress at high temperatures the interface traps become electrically active again and are evidently depassivated. These findings are in line with recently a published model of the effect of sodium on such interface states

Download Full-text

Excellent effects of hydrogen postoxidation annealing on inversion channel mobility of 4H-SiC MOSFET fabricated on (11 2 0) face

IEEE Electron Device Letters ◽

10.1109/55.974797 ◽

2002 ◽

Vol 23 (1) ◽

pp. 13-15 ◽

Cited By ~ 79

Author(s):

J. Senzaki ◽

K. Kojima ◽

S. Harada ◽

R. Kosugi ◽

S. Suzuki ◽

...

Keyword(s):

Channel Mobility ◽

Inversion Channel

Download Full-text

Gamma Irradiation Effects on 4H-SiC MOS Capacitors and MOSFETs

Materials Science Forum ◽

10.4028/www.scientific.net/msf.527-529.1063 ◽

2006 ◽

Vol 527-529 ◽

pp. 1063-1066 ◽

Cited By ~ 4

Author(s):

Ayayi Claude Ahyi ◽

S.R. Wang ◽

John R. Williams

Keyword(s):

Field Effect ◽

Gamma Dose ◽

Interface Traps ◽

Valence Band Edge ◽

Field Effect Mobility ◽

Irradiation Effects ◽

Mos Capacitors ◽

Channel Mobility ◽

Radiation Induced ◽

Radiation Tolerant

The effects of gamma radiation on field effect mobility and threshold voltage have been studied for lateral n-channel 4H-SiC MOSFETs passivated with nitric oxide. MOS capacitors (n and p) and n-channel lateral MOSFETs were irradiated unbiased (floating contacts) for a total gamma dose of 6.8Mrad (Si). The MOS capacitors were used to study the radiation-induced interface traps and fixed oxide charge that affect the performance of the MOSFETs. Radiationinduced interface traps were observed near the SiC valence band edge and just above mid-gap, and field effect channel mobility was reduced by 18-20% following irradiation. Even so, 4HMOSFETs appear to be more radiation tolerant than Si devices.

Download Full-text