Effect of nitric oxide annealing on the interface trap densities near the band edges in the 4H polytype of silicon carbide

Chung, Gil Yong; Tin, C. C.; Williams, John R.; McDonald, K.; Ventra, Massimiliano Di; Pantelides, Sokrates T.; Feldman, L. C.; Weller, Robert A.

doi:10.1063/1.126167

Cited by 402 publications

(197 citation statements)

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“…A key problem is the high density of so called near-interface traps (NITs) detected at the SiO 2 /4H-SiC interface with energy levels near the SiC conduction band edge that limit the electron channel mobility. [3][4][5][6] Currently thermal oxides grown or annealed in NO or N 2 O are the mainstream dielectrics but more reduction in NITs is needed. 7 Other large bandgap dielectrics such as AlN, Al 2 O 3 and HfO 2 have also been investigated.…”

Section: Introductionmentioning

confidence: 99%

Electrical characterization of amorphous Al2O3 dielectric films on n-type 4H-SiC

et al. 2018

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We report on the electrical properties of Al2O3 films grown on 4H-SiC by successive thermal oxidation of thin Al layers at low temperatures (200°C - 300°C). MOS capacitors made using these films contain lower density of interface traps, are more immune to electron injection and exhibit higher breakdown field (5MV/cm) than Al2O3 films grown by atomic layer deposition (ALD) or rapid thermal processing (RTP). Furthermore, the interface state density is significantly lower than in MOS capacitors with nitrided thermal silicon dioxide, grown in N2O, serving as the gate dielectric. Deposition of an additional SiO2 film on the top of the Al2O3 layer increases the breakdown voltage of the MOS capacitors while maintaining low density of interface traps. We examine the origin of negative charges frequently encountered in Al2O3 films grown on SiC and find that these charges consist of trapped electrons which can be released from the Al2O3 layer by depletion bias stress and ultraviolet light exposure. This electron trapping needs to be reduced if Al2O3 is to be used as a gate dielectric in SiC MOS technology.

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Section: Introductionmentioning

confidence: 99%

Electrical characterization of amorphous Al2O3 dielectric films on n-type 4H-SiC

et al. 2018

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“…Afanas'ev et al have suggested that carbon clusters at and near the interface form during oxidation [3,4], but the structure and dynamics of these clusters has not been established. Lipkin and Palmour found that, after oxidation, a 'reoxidation' step is necessary to produce high-quality oxides and SiC-SiO 2 interfaces [5,6]. During this step, oxygen is supplied as during oxidation, but the temperature is lowered so that no further oxidation takes place.…”

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Atomic-Scale Dynamics of the Formation and Dissolution of Carbon Clusters in SiO2

et al. 2001

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Oxidation of SiC produces SiO2 while CO is released. A 'reoxidation' step at lower temperatures is, however, necessary to produce high-quality SiO2. This step is believed to cleanse the oxide of residual C without further oxidation of the SiC substrate. We report first-principles calculations that describe the nucleation and growth of O-deficient C clusters in SiO2 under oxidation conditions, fed by the production of CO at the advancing interface, and their gradual dissolution by the supply of O under reoxidation conditions. We predict that both CO and CO2 are released during both steps.PACS numbers: 68.55. Ln, 68.35.Dv The most significant property of semiconductors is their ability to sustain heterogeneous n-type and p-type doping. This property, however, is eroded by high temperatures and high voltages that cause intrinsic excitation of electron-hole pairs across the band gap. As a result, semiconductors with significantly larger band gaps than silicon have been investigated as candidates for electronic devices suitable for high temperatures and high voltages. Silicon carbide is a particularly attractive candidate because its native oxide is SiO 2 which works so well as a dielectric in Si-based microelectronics. The presence of a third element, however, namely C, results in a wide range of phenomena that do not occur in the Si-SiO 2 system. In particular, oxidation of SiC entails the production of CO which effuses through the oxide [1,2]. Afanas'ev et al. have suggested that carbon clusters at and near the interface form during oxidation [3,4], but the structure and dynamics of these clusters has not been established. Lipkin and Palmour found that, after oxidation, a 'reoxidation' step is necessary to produce high-quality oxides and SiC-SiO 2 interfaces [5,6]. During this step, oxygen is supplied as during oxidation, but the temperature is lowered so that no further oxidation takes place. In contrast, post-oxidation heat treatment without the supply of O leads to an increase of charged defects in the oxide [7]. It is believed that the 'reoxidation' step cleanses the interface and bulk SiO 2 of residual carbon [3]. Duscher et al. recently presented direct experimental evidence for the existence of carbon in as-grown samples and its removal after reoxidation [8].The nucleation and growth of impurity clusters in semiconductors is a generic problem for which totalenergy calculations are well suited to provide detailed information. In this Letter we present the results of extensive first-principles density-functional calculations that allow us to give a detailed account of the nucleation and growth of O-deficient carbon clusters in SiO 2 during oxidation conditions and their dissolution during reoxidation conditions. Basically, a CO molecule, generated at the advancing interface and diffusing through the oxide, can bind weakly to an O site in the SiO 2 network. A second CO molecule, however, can bind to the first and the new complex is very stable. Additional CO molecules can extend the cluster. The process is ...

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“…12 These processes should remove carbon from the interface 9,10 or passivate carbon-cluster gap states by N incorporation. 11,12 However, even with these postoxidation processes, the DOS at the SiC-SiO 2 interface is still larger than the corresponding one at the Si-SiO 2 interface. It is certainly possible that the correct processing to completely avoid carbon-related defects has not been found yet.…”

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confidence: 99%

“…8 Much effort has been devoted to improvement of the interface quality between SiC and its native oxide. Promising processes for the reduction of the interface-state density are reoxidation, 9,10 NO annealing, 11 or annealing in ammonia. 12 These processes should remove carbon from the interface 9,10 or passivate carbon-cluster gap states by N incorporation.…”

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confidence: 99%

Can we make the SiC–SiO2 interface as good as the Si–SiO2 interface?

Ventra

2001

Applied Physics Letters

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Effect of nitric oxide annealing on the interface trap densities near the band edges in the 4H polytype of silicon carbide

Cited by 402 publications

References 9 publications

Electrical characterization of amorphous Al2O3 dielectric films on n-type 4H-SiC

Electrical characterization of amorphous Al2O3 dielectric films on n-type 4H-SiC

Atomic-Scale Dynamics of the Formation and Dissolution of Carbon Clusters in SiO2

Can we make the SiC–SiO2 interface as good as the Si–SiO2 interface?

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