Improved inversion channel mobility for 4H-SiC MOSFETs following high temperature anneals in nitric oxide

The use of phosphorous as a passivating agent for the SiO2/4H-SiC interface increases the field effect channel mobility of 4H-SiC MOSFET to twice the value, 30-40cm2/V-s, that is obtained with a high temperature anneal in nitric oxide (NO). A solid SiP2O7planar diffusion source is used to produce P2O5for the passivation of the interface. Incorporation of phosphorous into SiO2leads to formation of phosphosilicate glass (PSG) which is known to be a polar material causes device instability. With a new modified thin phosphorous (P) passivation process, as described in this abstract, we can improve the stability of MOSFETs significantly with mobility around 75cm2/V.s.

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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.

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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.

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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

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High-Mobility SiC MOSFETs with Alkaline Earth Interface Passivation

Materials Science Forum ◽

10.4028/www.scientific.net/msf.858.671 ◽

2016 ◽

Vol 858 ◽

pp. 671-676 ◽

Cited By ~ 18

Author(s):

Daniel J. Lichtenwalner ◽

Vipindas Pala ◽

Brett A. Hull ◽

Scott Allen ◽

John W. Palmour

Keyword(s):

Nitric Oxide ◽

Field Effect ◽

Alkaline Earth ◽

Phonon Scattering ◽

Breakdown Strength ◽

Field Effect Transistors ◽

Oxide Semiconductor ◽

Field Effect Mobility ◽

Channel Mobility ◽

Alkaline Earth Elements

Alkaline earth elements Sr and Ba provide SiO2/SiC interface conditions suitable for obtaining high channel mobility metal-oxide-semiconductor field-effect-transistors (MOSFETs) on the Si-face (0001) of 4H-SiC, without the standard nitric oxide (NO) anneal. The alkaline earth elements Sr and Ba located at/near the SiO2/SiC interface result in field-effect mobility (μFE) values as high as 65 and 110 cm2/V.s, respectively, on 5×1015 cm-3 Al-doped p-type SiC. As the SiC doping increases, peak mobility decreases as expected, but the peak mobility remains higher for Ba interface layer (Ba IL) devices compared to NO annealed devices. The Ba IL MOSFET field-effect mobility decreases as the temperature is increased to 150 °C, as expected when mobility is phonon-scattering-limited, not interface-trap-limited. This is in agreement with measurements of the interface state density (DIT) using the high-low C-V technique, indicating that the Ba IL results in lower DIT than that of samples with nitric oxide passivation. Vertical power MOSFET (DMOSFET) devices (1200V, 15A) fabricated with the Ba IL have a 15% lower on-resistance compared to devices with NO passivation. The DMOSFET devices with a Ba IL maintain a stable threshold voltage under NBTI stress conditions of-15V gate bias stress, at 150 °C for 100hrs, indicating no mobile ions. Secondary-ion mass-spectrometry (SIMS) analysis confirms that the Sr and Ba remain predominantly at the SiO2/SiC interface, even after high temperature oxide annealing, consistent with the observed high channel mobility after these anneals. The alkaline earth elements result in enhanced SiC oxidation rate, and the resulting gate oxide breakdown strength is slightly reduced compared to NO annealed thermal oxides on SiC.

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Sub-nm-Scale Depth Profiling of Nitrogen in NO- and N2-Annealed SiO2/4H-SiC(0001) Structures

Materials Science Forum ◽

10.4028/www.scientific.net/msf.963.226 ◽

2019 ◽

Vol 963 ◽

pp. 226-229

Author(s):

Kidist Moges ◽

Mitsuru Sometani ◽

Takuji Hosoi ◽

Takayoshi Shimura ◽

Shinsuke Harada ◽

...

Keyword(s):

Nitric Oxide ◽

High Temperature ◽

Photoelectron Spectroscopy ◽

Depth Profiling ◽

Annealing Duration ◽

Nanometer Scale ◽

Pure Nitrogen ◽

X Ray ◽

Initial Stage

We demonstrated an x-ray photoelectron spectroscopy (XPS)-based technique to reveal the detailed nitrogen profile in nitrided SiO2/4H-SiC structures with sub-nanometer-scale-resolution. In this work, nitric oxide (NO)- and pure nitrogen (N2)-annealed SiO2/4H-SiC(0001) structures were characterized. The measured results of NO-annealed samples with various annealing duration indicate that preferential nitridation just at the SiO2/SiC interfaces (~0.3 nm) proceeds in the initial stage of NO annealing and a longer duration leads to the distribution of nitrogen in the bulk SiO2 within few nanometers of the interface. The high-temperature N2 annealing was found to induce not only SiO2/SiC interface nitridation similarly to NO annealing but also SiO2 surface nitridation.

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Inversion channel mobility and interface state density of diamond MOSFET using N-type body with various phosphorus concentrations

Applied Physics Letters ◽

10.1063/1.5100328 ◽

2019 ◽

Vol 114 (24) ◽

pp. 242101 ◽

Cited By ~ 6

Author(s):

Tsubasa Matsumoto ◽

Hiromitsu Kato ◽

Toshiharu Makino ◽

Masahiko Ogura ◽

Daisuke Takeuchi ◽

...

Keyword(s):

Interface State ◽

State Density ◽

Interface State Density ◽

Channel Mobility ◽

Inversion Channel

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High Threshold Voltage Normally off Ultra-Thin-Barrier GaN MISHEMT with MOCVD-Regrown Ohmics and Si-Rich LPCVD-SiNx Gate Insulator

Energies ◽

10.3390/en13102479 ◽

2020 ◽

Vol 13 (10) ◽

pp. 2479

Author(s):

Hsiang-Chun Wang ◽

Hsien-Chin Chiu ◽

Chong-Rong Huang ◽

Hsuan-Ling Kao ◽

Feng-Tso Chien

Keyword(s):

Threshold Voltage ◽

Gate Insulator ◽

High Threshold ◽

Potential Candidate ◽

Channel Mobility ◽

Switching Power ◽

Selective Area ◽

Inversion Channel ◽

Threshold Voltage Distribution ◽

Dimensional Electron Gas

A high threshold voltage (VTH) normally off GaN MISHEMTs with a uniform threshold voltage distribution (VTH = 4.25 ± 0.1 V at IDS = 1 μA/mm) were demonstrated by the selective area ohmic regrowth technique together with an Si-rich LPCVD-SiNx gate insulator. In the conventional GaN MOSFET structure, the carriers were induced by the inversion channel at a high positive gate voltage. However, this design sacrifices the channel mobility and reliability because a huge number of carriers are beneath the gate insulator directly during operation. In this study, a 3-nm ultra-thin Al0.25Ga0.75N barrier was adopted to provide a two-dimensional electron gas (2DEG) channel underneath the gate terminal and selective area MOCVD-regrowth layer to improve the ohmic contact resistivity. An Si-rich LPCVD-SiNx gate insulator was employed to absorb trace oxygen contamination on the GaN surface and to improve the insulator/GaN interface quality. Based on the breakdown voltage, current density, and dynamic RON measured results, the proposed LPCVD-MISHEMT provides a potential candidate solution for switching power electronics.

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