Improved Channel Mobility in 4H-SiC MOSFETs by Boron Passivation

Okamoto, Daisuke; Sometani, Mitsuru; Harada, Shinsuke; Kosugi, Ryoji; Yonezawa, Yoshiyuki; Yano, Hiroshi

doi:10.1109/led.2014.2362768

Cited by 107 publications

(67 citation statements)

References 20 publications

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“…Introduction of foreign atoms such as phosphorus (P) [9], boron (B) [10], sodium (Na) [11], and barium (Ba) [12] into SiO2/SiC systems reduces the Dit (passivation of the interface levels), thus leading to the increase of the channel mobility. It is experimentally known that the foreign atoms mentioned above are distributed in the SiO2, and that the oxidation reaction is promoted during the passivation process.…”

mentioning

confidence: 99%

Microscopic mechanism of carbon annihilation upon SiC oxidation due to phosphorus treatment: Density functional calculations combined with ion mass spectrometry

Kobayashi¹,

Matsushita²,

Okuda³

et al. 2018

Appl. Phys. Express

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We report first-principles static and dynamic calculations that clarify the microscopic mechanism of carbon annihilation due to phosphorous treatment upon oxidation of silicon carbide (SiC). We identify the most stable form of the phosphorus (P) in the oxide as the four-fold coordinated with the dangling PO unit and find that the unit attracts carbon ejected from the interface, thus operating as a carbon absorber. This finding provides a microscopic reasoning for the first time for the promotion of the oxidation reaction on one hand and the annihilation of the C-related defects at the interface on the other. Secondary ion mass spectrometry measurements are also performed and the obtained carbon profile corroborates the theoretical finding above. 2The interface of a condensed matter and its oxidized film usually formed by the oxidation is ubiquitous in nature and provides an important stage in both science and technology. In semiconductor devices, for instance, the interface becomes a channel for the electric current and the band offset at the interface allows the gate controllability of the transistor action [1]. Hence the identification of the atomic structure and the clarification of its electronic functionality of the interface are challenging and demanded in nanoscience and technology.An example which has been insufficiently investigated in spite of its importance is the interface of silicon carbide (SiC) and silicon dioxide (SiO2). SiC is a candidate material for the sustainable power electronics in future due to its superior properties such as wide bandgap, high critical electric field and low intrinsic carrier concentration [2,3]. The additional but important advantage of SiC is that SiO2 films formed by the thermal oxidation can be used as gate insulating films in metal-oxide-semiconductor field effect transistors (MOSFETs) [3], ensuring the connectivity with the current Si technology.However, were carbon atoms not annihilated during the oxidation, the SiO2 films would not be realized. The fact is that, although SiC MOSFETs are fabricated, the mobility of the devices is lower than that of SiC bulk by two orders of magnitude [3]. This is certainly due to the interface state density, Dit, which is typically about 10 13 -10 14 cm -2 eV -1 [3,4,5] near the conduction-band edge (EC) of SiC which is higher by more than three orders of magnitude than that in typical SiO2/Si systems

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confidence: 99%

Microscopic mechanism of carbon annihilation upon SiC oxidation due to phosphorus treatment: Density functional calculations combined with ion mass spectrometry

Kobayashi¹,

Matsushita²,

Okuda³

et al. 2018

Appl. Phys. Express

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“…The characteristics of B-diffused MOSFETs are described in Ref. [7]. One of the most convenient ways to investigate the slow interface traps at the SiO 2 /4H-SiC interface is to measure the start-voltage dependence of C-V curves at a sufficiently low temperature, as originally proposed by Afanas'ev et al [14].…”

Section: Resultsmentioning

confidence: 99%

“…Si atoms are believed to be released from the interface during thermal oxidation both for the Si and SiC substrates to release the interface stress caused by volume expansion [31][32][33]. During the thermal annealing used for incorporating B atoms, the oxide thickness increased from 47 to 65 nm [7], meaning that there was additional thermal oxidation of the 4H-SiC substrate. A new interface is formed during this additional thermal oxidation, and B atoms are incorporated into the interface.…”

Section: Discussionmentioning

confidence: 99%

“…More recently, we have reported that the incorporation of boron (B) into a SiO 2 /4H-SiC(0001) interface reduces D it close to the conduction band edge of 4H-SiC [7]. A boron nitride (BN) planar diffusion source was used as the B source, and the fabricated MOSFETs exhibited a field-effect mobility of 102 cm 2 V −1 s −1 [7].…”

Section: −1mentioning

confidence: 99%

“…A boron nitride (BN) planar diffusion source was used as the B source, and the fabricated MOSFETs exhibited a field-effect mobility of 102 cm 2 V −1 s −1 [7].…”

Section: −1mentioning

confidence: 99%

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Effect of boron incorporation on slow interface traps in SiO2/4H-SiC structures

et al. 2017

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The reason for the effective removal of interface traps in SiO 2 /4H-SiC (0001) structures by boron (B) incorporation was investigated by employing lowtemperature electrical measurements. Low-temperature capacitance-voltage and thermal dielectric relaxation current measurements revealed that the density of electrons captured in slow interface traps in B-incorporated oxide is lower than that in dry and NO-annealed oxides. These results suggest that near-interface traps can be removed by B incorporation, which is considered to be an important reason for the increase in the field-effect mobility of 4H-SiC metal-oxide-semiconductor devices. A model for the passivation mechanism is proposed that takes account of stress relaxation during thermal oxidation.

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Unipolar Device in SiC : Diodes and MOSFET s

Ryu

2021

Wide Bandgap Semiconductors for Power Electronics

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Improved Channel Mobility in 4H-SiC MOSFETs by Boron Passivation

Cited by 107 publications

References 20 publications

Microscopic mechanism of carbon annihilation upon SiC oxidation due to phosphorus treatment: Density functional calculations combined with ion mass spectrometry

Microscopic mechanism of carbon annihilation upon SiC oxidation due to phosphorus treatment: Density functional calculations combined with ion mass spectrometry

Effect of boron incorporation on slow interface traps in SiO2/4H-SiC structures

Unipolar Device in SiC : Diodes and MOSFET s

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