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Title: Negative charge trapping effects in Al{sub 2}O{sub 3} films grown by atomic layer deposition onto thermally oxidized 4H-SiC

Abstract

This letter reports on the negative charge trapping in Al{sub 2}O{sub 3} thin films grown by atomic layer deposition onto oxidized silicon carbide (4H-SiC). The films exhibited a permittivity of 8.4, a breakdown field of 9.2 MV/cm and small hysteresis under moderate bias cycles. However, severe electron trapping inside the Al{sub 2}O{sub 3} film (1 × 10{sup 12} cm{sup −2}) occurs upon high positive bias stress (>10 V). Capacitance-voltage measurements at different temperatures and stress conditions have been used to determine an activation energy of 0.1 eV. The results provide indications on the possible nature of the trapping defects and, hence, on the strategies to improve this technology for 4H-SiC devices.

Authors:
 [1];  [2]; ; ;  [1]
  1. Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, Zona industriale – 95121 Catania (Italy)
  2. (Italy)
Publication Date:
OSTI Identifier:
22611422
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Advances; Journal Volume: 6; Journal Issue: 7; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ACTIVATION ENERGY; ALUMINIUM OXIDES; BREAKDOWN; CAPACITANCE; DEFECTS; DEPOSITION; HYSTERESIS; LAYERS; PERMITTIVITY; SILICON; SILICON CARBIDES; STRESSES; THIN FILMS; TRAPPING

Citation Formats

Schilirò, Emanuela, E-mail: emanuela.schiliro@imm.cnr.it, Dipartimento di Scienze Chimiche, Università degli Studi di Catania, and INSTM udr Catania, viale Andrea Doria 6, 95125, Catania, Lo Nigro, Raffaella, Fiorenza, Patrick, and Roccaforte, Fabrizio. Negative charge trapping effects in Al{sub 2}O{sub 3} films grown by atomic layer deposition onto thermally oxidized 4H-SiC. United States: N. p., 2016. Web. doi:10.1063/1.4960213.
Schilirò, Emanuela, E-mail: emanuela.schiliro@imm.cnr.it, Dipartimento di Scienze Chimiche, Università degli Studi di Catania, and INSTM udr Catania, viale Andrea Doria 6, 95125, Catania, Lo Nigro, Raffaella, Fiorenza, Patrick, & Roccaforte, Fabrizio. Negative charge trapping effects in Al{sub 2}O{sub 3} films grown by atomic layer deposition onto thermally oxidized 4H-SiC. United States. doi:10.1063/1.4960213.
Schilirò, Emanuela, E-mail: emanuela.schiliro@imm.cnr.it, Dipartimento di Scienze Chimiche, Università degli Studi di Catania, and INSTM udr Catania, viale Andrea Doria 6, 95125, Catania, Lo Nigro, Raffaella, Fiorenza, Patrick, and Roccaforte, Fabrizio. Fri . "Negative charge trapping effects in Al{sub 2}O{sub 3} films grown by atomic layer deposition onto thermally oxidized 4H-SiC". United States. doi:10.1063/1.4960213.
@article{osti_22611422,
title = {Negative charge trapping effects in Al{sub 2}O{sub 3} films grown by atomic layer deposition onto thermally oxidized 4H-SiC},
author = {Schilirò, Emanuela, E-mail: emanuela.schiliro@imm.cnr.it and Dipartimento di Scienze Chimiche, Università degli Studi di Catania, and INSTM udr Catania, viale Andrea Doria 6, 95125, Catania and Lo Nigro, Raffaella and Fiorenza, Patrick and Roccaforte, Fabrizio},
abstractNote = {This letter reports on the negative charge trapping in Al{sub 2}O{sub 3} thin films grown by atomic layer deposition onto oxidized silicon carbide (4H-SiC). The films exhibited a permittivity of 8.4, a breakdown field of 9.2 MV/cm and small hysteresis under moderate bias cycles. However, severe electron trapping inside the Al{sub 2}O{sub 3} film (1 × 10{sup 12} cm{sup −2}) occurs upon high positive bias stress (>10 V). Capacitance-voltage measurements at different temperatures and stress conditions have been used to determine an activation energy of 0.1 eV. The results provide indications on the possible nature of the trapping defects and, hence, on the strategies to improve this technology for 4H-SiC devices.},
doi = {10.1063/1.4960213},
journal = {AIP Advances},
number = 7,
volume = 6,
place = {United States},
year = {Fri Jul 15 00:00:00 EDT 2016},
month = {Fri Jul 15 00:00:00 EDT 2016}
}
  • Al{sub 2}O{sub 3} films were prepared by atomic layer deposition using trimethylaluminum and H{sub 2}O at 250 Degree-Sign C on 4H-SiC substrates and annealed at 1000 Degree-Sign C in N{sub 2}. The as-deposited and annealed Al{sub 2}O{sub 3} films were measured and analyzed near the Al{sub 2}O{sub 3}/SiC interfaces by using an X-ray photoelectron spectroscopy (XPS) with etching processing. The XPS results showed that as-deposited Al{sub 2}O{sub 3} films were O-rich and converted to anhydride Al{sub 2}O{sub 3} films after annealed at 1000 Degree-Sign C in N{sub 2}. Si suboxides were found both at as-deposited and annealed Al{sub 2}O{sub 3}/SiCmore » interfaces. Energy band shift between Al{sub 2}O{sub 3} and 4H-SiC was found after annealing. The conduction band offsets of as-grown and annealed Al{sub 2}O{sub 3}/SiC were 1.90 and 1.53 eV, respectively. These results demonstrated that Al{sub 2}O{sub 3} can be a good candidate to be applied in SiC metal-oxide-semiconductor devices.« less
  • The Al{sub 2}O{sub 3} film formed using an atomic layer deposition (ALD) method with trimethylaluminum as Al precursor and H{sub 2}O as oxidant at a high temperature (450 °C) effectively passivates the p-type surface conduction (SC) layer specific to a hydrogen-terminated diamond surface, leading to a successful operation of diamond SC field-effect transistors at 400 °C. In order to investigate this excellent passivation effect, we carried out an isotope analysis using D{sub 2}O instead of H{sub 2}O in the ALD and found that the Al{sub 2}O{sub 3} film formed at a conventional temperature (100 °C) incorporates 50 times more CH{sub 3} groups thanmore » the high-temperature film. This CH{sub 3} is supposed to dissociate from the film when heated afterwards at a higher temperature (550 °C) and causes peeling patterns on the H-terminated surface. The high-temperature film is free from this problem and has the largest mass density and dielectric constant among those investigated in this study. The isotope analysis also unveiled a relatively active H-exchange reaction between the diamond H-termination and H{sub 2}O oxidant during the high-temperature ALD, the SC still being kept intact. This dynamic and yet steady H termination is realized by the suppressed oxidation due to the endothermic reaction with H{sub 2}O. Additionally, we not only observed the kinetic isotope effect in the form of reduced growth rate of D{sub 2}O-oxidant ALD but found that the mass density and dielectric constant of D{sub 2}O-grown Al{sub 2}O{sub 3} films are smaller than those of H{sub 2}O-grown films. This is a new type of isotope effect, which is not caused by the presence of isotopes in the films unlike the traditional isotope effects that originate from the presence of isotopes itself. Hence, the high-temperature ALD is very effective in forming Al{sub 2}O{sub 3} films as a passivation and/or gate-insulation layer of high-temperature-operation diamond SC devices, and the knowledge of the aforementioned new isotope effect will be a basis for further enhancing ALD technologies in general.« less
  • Research on thin film deposited by atomic layer deposition (ALD) for laser damage resistance is rare. In this paper, it has been used to deposit TiO{sub 2}/Al{sub 2}O{sub 3} films at 110 deg. C and 280 deg. C on fused silica and BK7 substrates. Microstructure of the thin films was investigated by x-ray diffraction. The laser-induced damage threshold (LIDT) of samples was measured by a damage test system. Damage morphology was studied under a Nomarski differential interference contrast microscope and further checked under an atomic force microscope. Multilayers deposited at different temperatures were compared. The results show that the filmsmore » deposited by ALD had better uniformity and transmission; in this paper, the uniformity is better than 99% over 100 mm {Phi} samples, and the transmission is more than 99.8% at 1064 nm. Deposition temperature affects the deposition rate and the thin film microstructure and further influences the LIDT of the thin films. As to the TiO{sub 2}/Al{sub 2}O{sub 3} films, the LIDTs were 6.73{+-}0.47 J/cm{sup 2} and 6.5{+-}0.46 J/cm{sup 2} at 110 deg. C on fused silica and BK7 substrates, respectively. The LIDTs at 110 deg. C are notably better than 280 deg. C.« less
  • The interest in applying thin films on Si-wafer substrate for microelectromechanical systems devices by using atomic layer deposition (ALD) has raised the demand on reliable mechanical property data of the films. This study aims to find a quick method for obtaining nanoindentation hardness of thin films on silicon with improved reliability. This is achieved by ensuring that the film hardness is determined under the condition that no plastic deformation occurs in the substrate. In the study, ALD Al{sub 2}O{sub 3} films having thickness varying from 10 to 600 nm were deposited on a single-side polished silicon wafer at 300 °C. A sharpmore » cube-corner indenter was used for the nanoindentation measurements. A thorough study on the Si-wafer reference revealed that at a specific contact depth of about 8 nm the wafer deformation in loading transferred from elastic to elastic–plastic state. Furthermore, the occurrence of this transition was associated with a sharp increase of the power-law exponent, m, when the unloading data were fitted to a power-law relation. Since m is only slightly material dependent and should fall between 1.2 and 1.6 for different indenter geometry having elastic contact to common materials, it is proposed that the high m values are the results from the inelastic events during unloading. This inelasticity is linked to phase transformations during pressure releasing, a unique phenomenon widely observed in single crystal silicon. Therefore, it is concluded that m could be used to monitor the mechanical state of the Si substrate when the whole coating system is loaded. A suggested indentation depth range can then be assigned to each film thickness to provide guidelines for obtaining reliable property data. The results show good consistence for films thicker than 20 nm and the nanoindentation hardness is about 11 GPa independent of film thickness.« less
  • A mild N{sub 2}O plasma treatment technique (low power and low substrate temperature) for carbon materials' (including graphite and carbon nanotubes) functionalization followed by subsequent high-k dielectric atomic layer deposition (ALD) was developed. It was shown that N{sub 2}O plasma carbon functionalization leads to the formation of epoxide and carboxylic groups on the carbon surface which act as active centers for ALD and, as a result, conformal and uniform Al{sub 2}O{sub 3} and Ti{sub x}Al{sub 1-x}O{sub y} films' growth occurred on the carbon surfaces. It was shown that the electrical properties of multinary Ti{sub x}Al{sub 1-x}O{sub y} oxides are moremore » promising in comparison to single Al{sub 2}O{sub 3} oxide. Some electrical properties of the Ti{sub x}Al{sub 1-x}O{sub y} films observed were a high dielectric constant {approx}19, low leakage current density (<3 Multiplication-Sign 10{sup -5} A/cm{sup 2} at 1 MV/cm), and high breakdown field ({approx}5.5 MV/cm).« less