Kinetics of scanned probe oxidation: Space-charge limited growth

Dubois, Emmanuel; Bubendorff, Jean-Luc

doi:10.1063/1.373510

Cited by 100 publications

(72 citation statements)

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“…One of the advantages of using pulsed voltage processing is that the space charge that builds up at the oxide/Ge interface tends to vanish during the time in which the voltage is turned off. It has been proposed that this space charge buildup restricts the oxide growth and the application of pulsed voltages should minimize this effect [13][14][15][16][17]. Observe that the duty cycle of the pulse train used in this work is only 30%, thus the electric field is turned off for 70% of the tip oscillation cycle.…”

Section: Resultsmentioning

confidence: 99%

Submicron fabrication by local anodic oxidation of germanium thin films

Oliveira¹,

Medeiros‐Ribeiro²,

Azevedo³

2009

Nanotechnology

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Here we describe a lithography scheme based on the local anodic oxidation of germanium film by a scanning atomic force microscope in a humidity-controlled atmosphere. The oxidation kinetics of the Ge film were investigated by a tapping mode, in which a pulsed bias voltage was synchronized and applied with the resonance frequency of the cantilever, and by a contact mode, in which a continuous voltage was applied. In the tapping mode we clearly identified two regimes of oxidation as a function of the applied voltage: the trench width increased linearly during the vertical growth and increased exponentially during the lateral growth. Both regimes of growth were interpreted taking into consideration the Cabrera-Mott mechanism of oxidation applied to the oxide/Ge interface. We also show the feasibility of the bottom-up fabrication process presented in this work by showing a Cu nanowire fabricated on top of a silicon substrate.

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Section: Resultsmentioning

confidence: 99%

Submicron fabrication by local anodic oxidation of germanium thin films

Oliveira¹,

Medeiros‐Ribeiro²,

Azevedo³

2009

Nanotechnology

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“…Dubois and Bubendorff, 20 trying to account for space-charge limited growth, proposed a power-of-time law in the form h(t,V)…”

Section: à3mentioning

confidence: 99%

“…The mechanism and kinetics of Si oxidation surfaces by AFM has been extensively studied, [17][18][19][20] since the very first experiments. The use of low temperature oxidation theory 21 alone was unable to account for experimental evidence, therefore, several other theories were raised to explain different regimes.…”

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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“…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.…”

mentioning

confidence: 99%

“…[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.…”

mentioning

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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Kinetics of scanned probe oxidation: Space-charge limited growth

Cited by 100 publications

References 24 publications

Submicron fabrication by local anodic oxidation of germanium thin films

Submicron fabrication by local anodic oxidation of germanium thin films

Scanning probe oxidation of SiC, fabrication possibilities and kinetics considerations

Nanoscale space charge generation in local oxidation nanolithography

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