Interface states in high temperature SiC gas sensing

Ghosh, Ruby N.; Tobias, Peter S.; Ejakov, S.G.; Golding, B.

doi:10.1109/icsens.2002.1037271

Cited by 11 publications

(19 citation statements)

References 16 publications

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“…The defect density was obtained via the hi-low technique [15], by subtracting the quasi-static C-V curve, which includes the capacitance of the defects in series with the oxide capacitance, from the 1 MHz C-V characteristic, where the ac signal is too fast for the defects to follow. The defect densities of our devices [8] are comparable to state of the art oxides grown under similar conditions [16]. Within our measurement accuracy, the 1 MHz C-V characteristic in hydrogen at 700 K is what we would obtain for a MISiC device with no interface states.…”

Section: Resultsmentioning

confidence: 53%

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Interface states in high-temperature gas sensors based on silicon carbide

2003

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Silicon carbide (SiC)-based metal-insulator-semiconductor devices are attractive for gas sensing in automotive exhausts and flue gases. The response of the devices to reducing gases has been assumed to be due to a reduced metal work function at the metal-oxide interface that shifts the flat band capacitance to lower voltages. We have discovered that high temperature (700 K) exposure to hydrogen results not only in the flat-band voltage occurring at a more negative bias than in oxygen, but also in the transition from accumulation (high capacitance) to inversion (low capacitance) occurring over a relatively narrow voltage range. In oxygen, this transition is broadened indicating the creation of a high density of interface states. We present a model of the hydrogen/oxygen response based on two independent phenomena: a chemically induced shift in the metal-semiconductor work function difference and the passivation/creation of charged states at the SiO 2 -SiC interface that is much slower than the work function shift. We discuss the effect of these results on sensor design and the choice of operating point.

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Section: Resultsmentioning

confidence: 53%

“…Metal-insulator-silicon carbide (MISiC) structures have been used as sensors in these environments, with refractory metals as gates. Species that have been monitored with such MISiCs at high temperatures include hydrogen, hydrocarbons, nitrogen oxides, and fluorine containing gases [1]- [8].…”

Section: Introductionmentioning

confidence: 99%

Interface states in high-temperature gas sensors based on silicon carbide

2003

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“…One significant aspect about this result is that the slope of the C-V curve in the HfO 2 /SiGe did not change following PDA at 900 8C, while the slope decreased significantly in the HfSiO/SiGe in normalized capacitance data following PDA at 900 8C. Many reported data show that the slope in a C-V curve is influenced by the interfacial state [19][20][21]; the decrease in slope of the HfSiO/SiGe can therefore be caused by the generation of Ge i at the HfSiO/SiGe interface. In order to confirm the change in slope by Ge i , C-V characteristics between HfSiO ($6 nm)/SiGe and HfSiO($6 nm)/Si were compared.…”

Section: Experimental Methodsmentioning

confidence: 54%

Interfacial reaction induced strain relaxation in Hf-silicate film on strained Si_0.7Ge_0.3(001) as a function of annealing temperature

Kim

Kang

et al. 2013

Phys. Status Solidi A

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Hf-based dielectrics were prepared using atomic layer deposition in order to investigate the effect of Si incorporation on the interfacial reaction and thermal stability in HfO 2 films on SiGe substrates. Two concentrations [100% HfO 2 and 50% HfO 2 50% SiO 2 (HfSiO)] were used on strained Si 0.7 Ge 0.3 substrates; a partially-crystalline phase was observed in the asgrown HfO 2 film, and was not observed in the as-grown HfSiO film. Phase separation between the SiO x and HfO x in HfSiO film did occur, however, when the annealing temperature was increased to over 900 8C, leading to the out-diffusion of Si from the Si 0.7 Ge 0.3 substrate and the formation of a Ge-rich layer at the interface between HfSiO and Si 0.7 Ge 0.3 . Finally, the strain in the Si 0.7 Ge 0.3 substrate was relaxed, and interfacial states greatly increased in HfSiO/Si 0.7 Ge 0.3 with the 900 8C anneal.ß 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 Introduction As the size of Si-based metal-oxidesemiconductor (MOS) devices decrease and higher speeds are required for operation, advanced MOS structure research has focused on new potential materials for high performance applications. Among high mobility semiconductor materials, strained Si 1Àx Ge x has attracted both industry and academic research due to a higher hole mobility value (1050 cm 2 /V s at Si 0.2 Ge 0.8 ) than that of Si (505 cm 2 /V s) [1,2]. HfO 2 is an attractive material for the replacement of conventional SiO 2 ; a high dielectric constant (K ¼ 15-20) leads to increased thickness, which can reduce current leakage across the gate oxide through direct tunneling. Specifically, SiO 2 -incorporated HfO 2 films (Hf-silicate) show good thermal stability and an acceptable band offset value when in contact with Si [3,4]. However, Hf-silicate films can separate readily into SiO 2 and HfO 2 , depending on the film composition and annealing temperature [5,6]. In our previous reports, phase separation of HfSiO film on a Si substrate was observed after rapid thermal annealing (RTA) at 900 8C, leading to a downgrading of electrical properties [7]. We noted that the

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“…At temperatures above 700 K, refractory metal electrodes, such as Pd, Pt, and Ir, can efficiently dehydrogenate long-chain hydrocarbons. Following dehydrogenation at the heated gate, hydrogen diffuses into the structure reaching both the metal-oxide and oxide-SiC interfaces in less than 0.5 ms. 7 The chemical event at the sensing gate electrode is detected electronically by a change in the device potential.…”

Section: Sic Field-effect Gas Sensorsmentioning

confidence: 99%

SiC field-effect devices operating at high temperature

Ghosh

Tobias

2005

Journal of Elec Materi

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Field-effect devices based on SiC metal-oxide-semiconductor (MOS) structures are attractive for electronic and sensing applications above 250°C. The MOS device operation in chemically corrosive, high-temperature environments places stringent demands on the stability of the insulating dielectric and the constituent interfaces within the structure. The primary mode of oxide breakdown under these conditions is attributed to electron injection from the substrate. The reliability of n-type SiC MOS devices was investigated by monitoring the gate-leakage current as a function of temperature. We find current densities below 17 nA/cm 2 and 3 nA/cm 2 at electric field strengths up to 0.6 MV/cm and temperatures of 330°C and 180°C, respectively. These are promising results for high-temperature operation, because the optimum bias point for SiC MOS gas sensors is near midgap, where the field across the oxide is small. Our results are valid for n-type SiC MOS sensors in general and have been observed in both the 4H and 6H polytypes.

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Interface states in high temperature SiC gas sensing

Cited by 11 publications

References 16 publications

Interface states in high-temperature gas sensors based on silicon carbide

Interface states in high-temperature gas sensors based on silicon carbide

Interfacial reaction induced strain relaxation in Hf-silicate film on strained Si_0.7Ge_0.3(001) as a function of annealing temperature

SiC field-effect devices operating at high temperature

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Interface states in high temperature SiC gas sensing

Cited by 11 publications

References 16 publications

Interface states in high-temperature gas sensors based on silicon carbide

Interface states in high-temperature gas sensors based on silicon carbide

Interfacial reaction induced strain relaxation in Hf-silicate film on strained Si0.7Ge0.3(001) as a function of annealing temperature

SiC field-effect devices operating at high temperature

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Interfacial reaction induced strain relaxation in Hf-silicate film on strained Si_0.7Ge_0.3(001) as a function of annealing temperature