Modeling and Experimental Validation of Sharpening Mechanism Based on Thermal Oxidation for Fabrication of Ultra-Sharp Silicon Nanotips

Abstract

This paper aims at modeling the thermal oxidation of silicon pillars leading to the formation of very sharp silicon tips. The model is used to determine optimum process parameters with respect to the initial shape of the silicon pillars and the geometry of the desired tip. The modeling concept is to extend a previous approach, which predicts the oxidation mechanism of silicon cylinders versus their initial radius. The silicon pillar geometry is approximated by a superposition of silicon cylindrical structures featuring a local curvature radius. Experimental validation has been performed for several initial silicon pillar shapes, at 1000 C and 1100 C under dry oxidation conditions, leading to formation of very sharp silicon tips. The numerical predictions are shown to agree well with these experimental data. The motivation of this study aims at designing and fabricating a nanoelectromechanical filter device. Its vibrating part consists of a silicon nanotip, covered with a thin gold layer, the geometrical features of which affect the center frequency of the nanofilter device.

Two-dimensional thermal oxidation of nonplanar silicon surfaces

“…The thermal oxidation of nonplanar silicon structures also finds application in implementing nanosized struc tures such as silicon quantum dots, nanowires, and sil icon needles [3]. In fabricating such devices, the main advantage of thermal oxidation is the compatibility with the standard CMOS process.…”

Modeling of Stress-Retarded Thermal Oxidation of Nonplanar Silicon Structures for Realization of Nanoscale Devices

“…The thermal oxidation of nonplanar structures has found novel use in realizing nanoscale device structures such as silicon tips [1], silicon quantum dots [2], and silicon NWs [3]. The major advantage of the technique is its capability to maintain compatibility with standard CMOS processes that may or may not be the case with grown NW structures [4].…”

Spin-filter scanniing tunneliing microscopy : a novel technique for the analysis of spin polarization on magnetic surfaces and spintronic devices

“…Examples of observation of magnetic structure at high resolution includes domains in magnetic nanowires [72,73], the magnetic structure of vortex cores in thin films [74] and even the (anti)ferromagnetic coupling of single magnetic adatoms on magnetic surfaces [75]. And there is also the possibility of manipulating the magnetic structure using the dipolar coupling due to the field from the tip (which can be avoided with antiferromagnetic tips [76]) or using current-induced switching [77].…”

“…Another advantage is that it does not require knowledge of the spinaveraged electronic structure, since they only measure a spin-valve effect. On the other hand, one must be careful that the bulk tips used may generate too large stray fields, a problem that is avoided in SP-STS by the use of antiferromagnetic tips [76]. More relevant, the magnetization modulation in this technique requires proper deconvolution of magnetostriction effects in the tip which could add spurious contribution to the dI/d⃗ m T signal.…”

“…Later refinements [71,72] allowed better numerical agreement with previous twodimensional experimental data [31,70]. Though modern implementation of simulators can give an account of advanced isolation techniques [73], even nowadays it is required to use analytical tools [74] with limited applicability as a fallback for simulating oxidation of three-dimensional sharp structures [75,76]. Therefore we took an experimental approach as a guide in the fabrication of SF-STM probes.…”