Hydrogen Incorporation Dependence on the Thermal Growth Route in Dielectric/SiC Structures

Abstract

The incorporation of hydrogen in dielectric/SiC structures and Pt/dielectric/SiC structures whose dielectric films were thermally grown in O 2 , NO, or O 2 followed by annealing in NO was investigated. The amount and the distribution of hydrogen incorporated and the capacitance-voltage characteristics were observed to be dependent on the thermal growth route employed. Hydrogen was mainly incorporated in the dielectric film/SiC interface region and larger amounts were incorporated when the Pt electrode was used. Annealing in hydrogen increased the negative shift in the flatband voltage, which was more pronounced when the Pt electrode was used in the case of NO-annealed To overcome the limits of silicon-based power devices, new semiconductor materials are necessary. Silicon carbide (SiC) is a wide bandgap semiconductor that presents adequate properties for high-power, high-temperature, and high-frequency electronics. These characteristics have been recently explored in the first commercially available metal-oxide-semiconductor field effect transistors (MOSFETs).1 However, reducing the density of electron traps at and near the SiO 2 /semiconductor interface, to improve the channel carrier mobility 2 and reliability of MOSFET devices, still remains as the main technological challenge. 3,4 The high density of interface states (D it ) in the SiO 2 /SiC interface region has been attributed to carbon related defects generated during the thermal oxidation of the SiC. [5][6][7] In order to improve the quality of this interface, post-oxidation annealing (POA) in nitric oxide (NO) has been employed as a successful method to reduce D it and to improve device reliability. 4,8 The effect of the incorporation of N was related to both the removal and the passivation of residual C in the dielectric/SiC interface region.9-11 The use of POA in H 2 also led to reduction in D it below the conduction band for n-type 4H-SiC (0001) MOS structures 12 and improve the channel mobility of 4H-SiC (0001) MOSFETs. 13 Moreover, combining POAs in NO and in H 2 using platinum (Pt) as the electrode metal caused a complementary reduction in D it 10,14 and enhanced field-effect mobility in 4H-SiC (0001) MOSFETs 15 compared with only NO or only H 2 annealings. The passivation effect of POA in H 2 has been investigated only in the case of thermal growth in O 2 with and without POA in NO, but the consequences of POA in H 2 in dielectric films directly grown in NO still remain unknown. Results for dielectric films grown on the carbon face of the SiC single-crystal indicate that the direct growth in NO led to better breakdown characteristics than NO-annealed oxides.3 Reliability results for silicon-faced 4H-SiC by Jamet et al.9 also revealed that dielectric films grown directly in NO exhibit a higher resistance to high field stress than previously grown dry oxide films annealed in NO. Furthermore, MOS structures with dielectric films grown in NO presented superior capacitance-voltage (C-V) characteristics than SiO 2 /SiC annealed in NO. 16,17 Therefore...