Predictive model for scanned probe oxidation kinetics

Dagata, John A.; Pérez‐Murano, F.; Abadal, G.; Morimoto, Kiyoshi; Inoue, Takahito; Itoh, J.; Yokoyama, Hiroshi

doi:10.1063/1.126451

Cited by 109 publications

(99 citation statements)

References 23 publications

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“…is predominant, but over time a second indirect path of the oxidation occurs 19 in which the charged defects are treated as reaction intermediates. Considering SiC instead of Si, the direct anodic reaction becomes…”

Section: à3mentioning

confidence: 99%

Scanning probe oxidation of SiC, fabrication possibilities and kinetics considerations

Lorenzoni

Torre

2013

Applied Physics Letters

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We report the outcome of atomic force microscopy local anodic oxidation experiments on 6H-SiC in air. Oxide thickness can be easily tuned by varying applied voltage and pulse duration. The height and the aspect ratio of single dots produced by single DC pulses are remarkably higher than what was reported previously, with self limiting heights exceeding 100 nm. We propose that the diminished density and the change in chemical composition of the oxide grown on SiC with respect to oxide grown under similar condition on Si cause a drop in the activation energy of oxanions diffusion within the newly formed oxide layer. V C 2013 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4825265] Silicon carbide is a wide gap semiconductor extensively employed in microelectronics industry. Due to its high thermal conductivity, high temperature operation, and chemical inertness, it is used as a valuable alternative to silicon for devices operating in hard conditions. Remarkably, SiC is the only semiconductor (except Si) whose native oxide is SiO 2 . However, SiC oxidation could result in mixed oxides products containing C inclusions. State-of-the-art technology in patterning semiconductor substrates mainly relies on mask-based techniques such as optical lithography or mask-less techniques like electron beam lithography, which are particularly suited for industrial applications such as large scale production in microelectronics and microfabrication, in general. Among all the alternatives, several promising scanning probe-related lithographies (SPLs) also emerged 1-4 as an affordable and very versatile nanofabrication technique. The advantages of using an atomic force microscope (AFM) reside in the in-line nanometric accuracy and in the possibility of directly applying multistep processes on pre-patterned substrates with no need for photoresist coatings and/or alignment tools. This makes SPL an ideal tool for flexible and fast prototyping of custom nanodevices. Few works have addressed the tip induced oxidation of SiC (Refs. 5-7) and none extensively explored the kinetics involved.In this work, we present the outcome of field induced oxidation (FIO) experiments in contact mode on 6H-SiC (0001) surface including: single pulse oxidation (pulse time ranging from 0.1 to 30 s), patterning examples (single lines and 3D patterns), and HF etch tests. The schematic of FIO is depicted in Fig. 1(a). By means of preliminary HF etching, we removed SiC native oxide layer to end up with an hydroxyl terminated surface. 8 On such surface, we were able to produce controlled single oxide dots for long oxidation times (>10 s), obtaining unexpected height and aspect ratio (height % 100 nm, full width at half maximum (FWHM) % 350 nm) in comparison with most FIO experiments (Figs. 1(b) and 1(c)). In order to have a quantitative explanation of the phenomenon, we compared the experimental data with available models dealing with Si probe oxidation in air. We estimated both oxide density and expansion rate by means of a wet etching test (dilute aqueous HF dis...

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Section: à3mentioning

confidence: 99%

Scanning probe oxidation of SiC, fabrication possibilities and kinetics considerations

Lorenzoni

Torre

2013

Applied Physics Letters

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“…[16][17][18][19][20] The kinetics of the oxidation process is influenced by the generation of a space charge. [21][22][23] The model by Dagata et al 21,24 considers two competing mechanisms, a fast oxidation process that applies to the initial stages ͑below 1 s͒ and a slower, indirect process that applies for longer oxidation times and involves space charge. Dubois and Bubendorff's model is based on a charge trapping-detrapping mechanism.…”

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confidence: 99%

Nanoscale space charge generation in local oxidation nanolithography

Chiesa¹,

García²

2010

Applied Physics Letters

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We have measured the surface potential and the space charge generated during the first stages of atomic force microscopy field-induced oxidation. Space charge densities are about 10 17 cm −3 for oxidation times below 10 ms. In a dry atmosphere, the surface potential is negative. However, in humid air the surface potential could be either positive or negative. This effect is attributed to a screening effect of the water molecules. These results explain and support the use of local oxidation patterns as templates for building molecular architectures. They also establish the space charge build up as an intrinsic feature in local oxidation experiments. © 2010 American Institute of Physics. ͓doi:10.1063/1.3459976͔Atomic force microscopy ͑AFM͒ oxidation nanolithography is a robust and flexible tip-based nanofabrication method [1][2][3][4][5] that is used to fabricate high resolution patterns and nanoscale devices. Thus, templates to build molecular architectures, 6,7 resist masks, 8 nanomechanical resonators, 9,10 or several nanoelectronic devices and transistors [11][12][13][14] have been fabricated by local oxidation. In AFM oxidation, the tip is used as a cathode and the water meniscus formed between the tip and the surface is the source of the oxyanions species. 15 The strong localization of the electrical field lines near the tip apex and the lateral confinement of the oxyanions species within the liquid meniscus give rise to a nanometer-size oxide dot. [16][17][18][19][20] The kinetics of the oxidation process is influenced by the generation of a space charge. [21][22][23] The model by Dagata et al. 21,24 considers two competing mechanisms, a fast oxidation process that applies to the initial stages ͑below 1 s͒ and a slower, indirect process that applies for longer oxidation times and involves space charge. Dubois and Bubendorff's model is based on a charge trapping-detrapping mechanism. 23 Most of the AFM oxidation nanolithography applications involve oxidation times below 1 s. Recently, local oxide patterns have been used as high resolution templates for the growth of functional materials such as protein carriers 7 or single molecule magnets. 25 The underlying mechanism behind the organization of molecular architectures is based on the electrostatic interactions between the charged or polarized molecules and the space charges trapped inside the local oxides. However, there is no experimental evidence that supports the existence of space charges for short oxidation times. In addition, the sign of the charge has not been measured.Here, we perform Kelvin probe force microscopy ͑KPFM͒ experiments to determine the space charge sign and density. The measurements establish the presence of a space charge build up during the earlier stages of the oxidation process ͑below 10 ms͒. The sign of the apparent space charge depends on the relative humidity inside the chamber where the KPFM measurements are performed. In dry conditions ͑N 2 gas environment͒ the observed charge is always negative. However, in the presence of wat...

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“…Since the molecular volume of the Hf oxide layer is larger than that of Hf itself, the expansion of oxide volume causes stress along the growth direction in a limited local space at the Hf/HfO x interface, thus pushing the HfO x layer upwards to form a protrusion. The higher oxide protrusion lowers the electric field between the tip and the surface, resulting in a decrease in the oxide growth rate due to an accumulation of dielectric material and ionic space charges trapped near the substrate/oxide interface [17,18]. Figure 4(a) shows the two-dimensional AFM surface topography after anodic nano-oxidation lithography, and figure 4(b) demonstrates the profile of the created oxide lines with respect to applied bias voltages up to 10 V at 75% relative humidity.…”

Section: Resultsmentioning

confidence: 99%

“…Several phenomenological models, such as the empirical power law [17,18], the logarithmic function of the applied voltage duration [19] and the inverse exponential growth (IEG) function [20,21] using the potential distribution in the oxide layer. This study shows that SPL grown HfO x data were best fitted to the IEG model, which defines the oxide thickness with the following equations:…”

Section: Resultsmentioning

confidence: 99%

Local oxidation nanolithography on Hf thin films using atomic force microscopy (AFM)

Büyükköse¹,

Okur²,

Aygün³

2009

J. Phys. D: Appl. Phys.

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Well controlled Hf oxide patterns have been grown on a flat Hf thin film surface produced by the dc magnetron sputtering method on Si and SiO x substrates. These patterns have been created by using the technique of semi-contact scanning probe lithography (SC-SPL). The thickness and width of the oxide patterns have been measured as a function of applied voltage, duration and relative humidity. There is a threshold voltage even at 87% humidity, due to insufficient energy required to start the oxide growth process for a measurable oxide protrusion. Electrical characterization was also performed via the I -V curves of Hf and HfO x structures, and the resistivity of HfO x was found to be 4.284 × 10 9 cm. In addition to the I -V curves, electric force microscopy and spreading surface resistance images of Hf and HfO x were obtained.

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Predictive model for scanned probe oxidation kinetics

Cited by 109 publications

References 23 publications

Scanning probe oxidation of SiC, fabrication possibilities and kinetics considerations

Scanning probe oxidation of SiC, fabrication possibilities and kinetics considerations

Nanoscale space charge generation in local oxidation nanolithography

Local oxidation nanolithography on Hf thin films using atomic force microscopy (AFM)

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