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Title: Activation energy of negative fixed charges in thermal ALD Al{sub 2}O{sub 3}

Abstract

A study of the thermally activated negative fixed charges Q{sub tot} and the interface trap densities D{sub it} at the interface between Si and thermal atomic-layer-deposited amorphous Al{sub 2}O{sub 3} layers is presented. The thermal activation of Q{sub tot} and D{sub it} was conducted at annealing temperatures between 220 °C and 500 °C for durations between 3 s and 38 h. The temperature-induced differences in Q{sub tot} and D{sub it} were measured using the characterization method called corona oxide characterization of semiconductors. Their time dependency were fitted using stretched exponential functions, yielding activation energies of E{sub A} = (2.2 ± 0.2) eV and E{sub A} = (2.3 ± 0.7) eV for Q{sub tot} and D{sub it}, respectively. For annealing temperatures from 350 °C to 500 °C, the changes in Q{sub tot} and D{sub it} were similar for both p- and n-type doped Si samples. In contrast, at 220 °C the charging process was enhanced for p-type samples. Based on the observations described in this contribution, a charging model leading to Q{sub tot} based on an electron hopping process between the silicon and Al{sub 2}O{sub 3} through defects is proposed.

Authors:
 [1];  [2];  [2]; ; ;  [1]
  1. Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstr. 2, 79110 Freiburg (Germany)
  2. (Germany)
Publication Date:
OSTI Identifier:
22594342
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 109; Journal Issue: 6; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ACTIVATION ENERGY; ALUMINIUM OXIDES; ANNEALING; DEFECTS; DENSITY; DEPOSITION; DOPED MATERIALS; ELECTRONS; INTERFACES; LAYERS; SEMICONDUCTOR MATERIALS; SILICON; TEMPERATURE RANGE 0400-1000 K

Citation Formats

Kühnhold-Pospischil, S., Institute of Physical Chemistry, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104 Freiburg, Freiburg Materials Research Center FMF, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg, Saint-Cast, P., Richter, A., and Hofmann, M. Activation energy of negative fixed charges in thermal ALD Al{sub 2}O{sub 3}. United States: N. p., 2016. Web. doi:10.1063/1.4960097.
Kühnhold-Pospischil, S., Institute of Physical Chemistry, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104 Freiburg, Freiburg Materials Research Center FMF, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg, Saint-Cast, P., Richter, A., & Hofmann, M. Activation energy of negative fixed charges in thermal ALD Al{sub 2}O{sub 3}. United States. doi:10.1063/1.4960097.
Kühnhold-Pospischil, S., Institute of Physical Chemistry, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104 Freiburg, Freiburg Materials Research Center FMF, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg, Saint-Cast, P., Richter, A., and Hofmann, M. Mon . "Activation energy of negative fixed charges in thermal ALD Al{sub 2}O{sub 3}". United States. doi:10.1063/1.4960097.
@article{osti_22594342,
title = {Activation energy of negative fixed charges in thermal ALD Al{sub 2}O{sub 3}},
author = {Kühnhold-Pospischil, S. and Institute of Physical Chemistry, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104 Freiburg and Freiburg Materials Research Center FMF, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg and Saint-Cast, P. and Richter, A. and Hofmann, M.},
abstractNote = {A study of the thermally activated negative fixed charges Q{sub tot} and the interface trap densities D{sub it} at the interface between Si and thermal atomic-layer-deposited amorphous Al{sub 2}O{sub 3} layers is presented. The thermal activation of Q{sub tot} and D{sub it} was conducted at annealing temperatures between 220 °C and 500 °C for durations between 3 s and 38 h. The temperature-induced differences in Q{sub tot} and D{sub it} were measured using the characterization method called corona oxide characterization of semiconductors. Their time dependency were fitted using stretched exponential functions, yielding activation energies of E{sub A} = (2.2 ± 0.2) eV and E{sub A} = (2.3 ± 0.7) eV for Q{sub tot} and D{sub it}, respectively. For annealing temperatures from 350 °C to 500 °C, the changes in Q{sub tot} and D{sub it} were similar for both p- and n-type doped Si samples. In contrast, at 220 °C the charging process was enhanced for p-type samples. Based on the observations described in this contribution, a charging model leading to Q{sub tot} based on an electron hopping process between the silicon and Al{sub 2}O{sub 3} through defects is proposed.},
doi = {10.1063/1.4960097},
journal = {Applied Physics Letters},
number = 6,
volume = 109,
place = {United States},
year = {Mon Aug 08 00:00:00 EDT 2016},
month = {Mon Aug 08 00:00:00 EDT 2016}
}
  • Our study compares the physical, chemical and electrical properties of Al 2O 3 thin films deposited on gallium polar c- and nonpolar m -plane GaN substrates by atomic layer deposition (ALD). Correlations were sought between the film's structure, composition, and electrical properties. The thickness of the Al 2O 3 films was 19.2 nm as determined from a Si witness sample by spectroscopic ellipsometry. We measured the gate dielectric was slightly aluminum-rich (Al:O=1:1.3) from X-ray photoelectron spectroscopy (XPS) depth profile, and the oxide-semiconductor interface carbon concentration was lower on c -plane GaN. The oxide's surface morphology was similar on both substrates,more » but was smoothest on c -plane GaN as determined by atomic force microscopy (AFM). Circular capacitors (50-300 μm diameter) with Ni/Au (20/100 nm) metal contacts on top of the oxide were created by standard photolithography and e-beam evaporation methods to form metal-oxide-semiconductor capacitors (MOSCAPs). Moreover, the alumina deposited on c -plane GaN showed less hysteresis (0.15 V) than on m -plane GaN (0.24 V) in capacitance-voltage (CV) characteristics, consistent with its better quality of this dielectric as evidenced by negligible carbon contamination and smooth oxide surface. These results demonstrate the promising potential of ALD Al 2O 3 on c -plane GaN, but further optimization of ALD is required to realize the best properties of Al 2O 3 on m -plane GaN.« less
  • Solvent-refined lignite (SRL) can be produced by treating lignite (not dried) with CO-H/sub 2/, donor solvent and high temperature. This reactive black solid softens at about 150/sup 0/C, is soluble in many organic solvents, is very low in ash and sulfur, and appears to be a good feedstock for further upgrading. Thus, a wide-ranging study was undertaken to determine the best reducing conditions for converting SRL to light distillable liquid fuels and/or chemical feedstocks. Batch autoclave studies were carried out in the temperature range of 375-450/sup 0/C, hydrogen pressure range of 1500-4500 psi, with catalysts Ni-Mo-Al/sub 2/O/sub 3/, Co-Mo-Al/sub 2/O/submore » 3/, Ni-W-Al/sub 2/O/sub 3/. Ni-W-SiO/sub 2/-Al/sub 2/O/sub 3/, SiO/sub 2/-Al/sub 2/O/sub 3/, Al/sub 2/O/sub 3/,SnCl/sub 2/, and presulfided catalysts Ni-Mo-Al/sub 2/O/sub 3/, Co-Mo-Al/sub 2/O/sub 3/, Ni-W-Al/sub 2/O/sub 3/. Varying amounts of the solvents tetrahydrofuran, tetralin, napthalene, and FS-120 petroleum fraction were also studied. Reductions without any solvent were studied too and were quite successful. The results were evaluated in terms of the amount of light liquids produced, deoxygenation, denitrification, hydrogen-carbon ratios, aromatic-aliphatic hydrogen ratios, and benzene solubility of unconverted material. Best results were obtained with a presulfided Ni-Mo-Al/sub 2/O/sub 3/ catalyst at 450/sup 0/C, operating pressure of about 3500 psi with a 1:1 SRL-tetralin solvent ratio (90 percent overall conversion, approx.20 percent light liquid (1), 15 percent light oil (2), 20 percent heavy oil (3 and 4), 10 percent unconverted). However, operating without any solvent also gave satisfactory results (88 percent overall conversion, 40 percent light liquid, 10 percent light oil, 10 percent heavy oil, 12 percent unconverted. Detailed gas chromatography-mass spectrometry (GC-MS) studies of selected liquid fractions indicate a high degree of aromaticity as tetralins, hydrophenanthrenes, and hydropyrenes.« less
  • The effect of deposition temperature (T{sub dep}) and subsequent annealing time (t{sub anl}) of atomic layer deposited aluminum oxide (Al{sub 2}O3) films on silicon surface passivation (in terms of surface recombination velocity, SRV) is investigated. The pristine samples (as-deposited) show presence of positive fixed charges, Q{sub F}. The interface defect density (D{sub it}) decreases with increase in T{sub dep} which further decreases with t{sub anl} up to 100s. An effective surface passivation (SRV<8 cm/s) is realized for T{sub dep} ≥ 200 °C. The present investigation suggests that low thermal budget processing provides the same quality of passivation as realized bymore » high thermal budget process (t{sub anl} between 10 to 30 min)« less
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