Rearrangement of the oxide-semiconductor interface in annealed Al2O3∕4H-SiC structures

Abstract

Al 2 O 3 films with different thicknesses have been deposited on n-type ͑nitrogen-doped͒ 4H-SiC͑0001͒ epitaxial samples by atomic layer chemical vapor deposition at 300°C and subsequently annealed in Ar atmosphere at temperatures up to 1000°C. The Al 2 O 3 /4H-SiC structures were analyzed by x-ray photoelectron spectroscopy ͑XPS͒, secondary ion mass spectrometry ͑SIMS͒, and transmission electron microscopy ͑TEM͒. The XPS and SIMS results indicate that the average composition in the wider interface area does not significantly change due to the annealing. However, as revealed by the TEM investigations in combination with XPS, the as-grown samples exhibit a double interface created by an intermediate suboxide SiO Because of its wide band gap ͑ϳ3.2 eV for polytype 4H͒, SiC is suitable for applications related to high power, high frequency, and high temperatures. In recent years, investigations for alternative dielectrics for device applications have become of great interest. Al 2 O 3 is one of the few pure metal oxides exhibiting a high dielectric constant ͑ ϳ 10͒, a relatively wide band gap ͑E g ϳ 6.2 eV͒, and a good thermal stability; moreover, compared to ZrO 2 or HfO 2 it displays higher conduction and valence band offsets, ⌬E c = 1.7 eV and ⌬E v = 1.2 eV, relative to 4H-SiC. 1,2 It has been shown that high quality Al 2 O 3 films can be grown on SiC by atomic layer chemical vapor deposition ͑ALCVD͒. 3 In previous studies, 4-6 electrical characterization such as capacitancevoltage ͑CV͒ and thermal dielectric relaxation current measurements of Al 2 O 3 /4H-SiC capacitors were reported. In fact, annealing in Ar above the crystallization temperature ͑ϳ900°C͒ was found to significantly enhance the electrical properties of the Al 2 O 3 / SiC interface and promote formation of the ␥ phase of Al 2 O 3 . Furthermore, it has been revealed that the interface properties of those annealed structures are superior to the ones of SiO 2 /4H-SiC interfaces, since the density of electron traps close to the conduction band minimum is reduced, 4 as required for improved channel mobility in a metal-oxide-SiC field effect transistors. In this study, the Al 2 O 3 /4H-SiC interface was investigated on as-grown and annealed samples using angle resolved x-ray photoelectron spectroscopy ͑AR-XPS͒, transmission electron microscopy ͑TEM͒, and secondary ion mass spectrometry ͑SIMS͒. An ultimate goal is to correlate the structural and compositional properties of the interface with the previously reported electrical characteristics.The Al 2 O 3 layers have been grown by ALCVD on Sifaced, n-type 4H-SiC samples with a 10 m thick epilayer ͑net doping level of 2 ϫ 10 15 cm −3 ͒ on a highly doped substrate ͑net doping level of 1 ϫ 10 18 cm −3 ͒, oriented 8°off the ͑0001͒ direction, purchased from Cree, Inc. Details of the cleaning and growth procedure can be found elsewhere. 4,5 For the AR-XPS measurements, 5 and 8 nm thick Al 2 O 3 layers were grown while thicker layers ͑ϳ110-120 nm͒ were deposited for the TEM and SIMS measurements. Annealing treatm...

Enhancement in interface robustness regarding thermal oxidation in nanostructured Al2O3 deposited on 4H-SiC

“…The interlayer thickness increased after annealing at 1000°C in Ar, which also triggered Si diffusion into the dielectric layer as evidenced by secondary ion mass spectrometry. 5 The thickness of a SiO 2 interlayer has significant impact on channel mobility for Al 2 O 3 / 4H-SiC MOSFETs. 6 Thus, controlling the transport of oxygen through Al 2 O 3 is mandatory.…”

Decoupling the Effects of Mass Density and Hydrogen-, Oxygen-, and Aluminum-Based Defects on Optoelectronic Properties of Realistic Amorphous Alumina

“…Amorphous alumina (AlO x ) has been considered in several technological applications, not only because of passivating and insulating properties, but also because of its high dielectric constant and reflectivity in the visible. − The AlO x thin layer can be deposited via a variety of techniques ranging from vacuum to nonvacuum techniques such as sputtering, chemical vapor deposition or atomic layer deposition . However, it is well-known that these processes introduce impurities from precursor chemical species used during film deposition, as hydrogen. − Unfortunately, it is difficult to quantitatively probe the H content in a film, particularly unbonded H formed during annealing under H 2 atmosphere and incorporated within AlO x bulk or at the interface AlO x /Si creating blistering phenomena .…”

Atomic spectrometry update. Industrial analysis: metals, chemicals and advanced materials

“…Avice et al prepared films of aluminium oxide on n-type (nitrogen doped) 4H-SiC (001) epitaxial samples using atomic layer chemical vapour deposition. 298 The samples were deposited at 300 C and were then annealed in an argon atmosphere at 1000 C. The structures of the materials were analyzed by a series of techniques including SIMS, XPS and TEM. The SIMS and XPS results indicated that the average composition in the wider interface was not changed significantly by the annealing process.…”