Emile van der Drift

Size-dependent effective Young’s modulus of silicon nitride cantilevers

The effective Young’s modulus of silicon nitride cantilevers is determined for thicknesses in the range of 20–684 nm by measuring resonance frequencies from thermal noise spectra. A significant deviation from the bulk value is observed for cantilevers thinner than 150 nm. To explain the observations we have compared the thickness dependence of the effective Young’s modulus for the first and second flexural resonance mode and measured the static curvature profiles of the cantilevers. We conclude that surface stress cannot explain the observed behavior. A surface elasticity model fits the experimental data consistently.

Sub-10-nm nanolithography with a scanning helium beam

Scanning helium ion beam lithography is presented as a promising pattern definition technique for dense sub-10-nm structures. The powerful performance in terms of high resolution, high sensitivity, and a low proximity effect is demonstrated in a hydrogen silsesquioxane resist.

Nature of defects in the Si‐SiO2 system generated by vacuum‐ultraviolet irradiation

We have used high‐frequency and quasi‐static capacitance‐voltage measurements to study the properties of interface states generated upon vacuum‐ultraviolet irradiation under positive gate bias followed by neutralization of the holes trapped in the oxide. The data indicate the exclusive generation of fast donor‐type states that anneal at room temperature. We propose that these states explain the turn‐around effect and annealing of positive charge.

Electroless Silver Deposition in 100 nm Silicon Structures

A new and simple method is described to plate silicon structures with metallic silver for ultralarge-scale integration in dimensions down to 100 nm at an aspect ratio of 4.25. The silver deposition is initiated by an exchange reaction of silicon with silver ions, and the subsequent layer growth of the activated wafers occurs by electroless plating from supersaturated aqueous silver salt solutions at pH ∼ 11. No extra reducing agents are needed since silver ions are reduced at the catalytic silver surface by hydroxyl ions. The spontaneous ion-metal transition only proceeds at pH ∼ 11 and is likely mediated by the formation of subnanometer-sized [Ag 4 (OH) 2 ] 2+ clusters. The silver plating proceeds more easily in smaller structures and yields void-free, crystallized deposits.

Nanofabrication with a helium ion microscope

The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valuable signal for high-resolution imaging as well as a mechanism for very precise nanofabrication. The low proximity effects, due to the low yield of backscattered ions and the confinement of the forward scattered ions into a narrow cone, enable patterning of ultra-dense sub-10 nm structures. This paper presents various nanofabrication results obtained with direct-write, with scanning helium ion beam lithography, and with helium ion beam induced deposition.

Polarization tomography of metallic nanohole arrays.

We report polarization tomography experiments on metallic nanohole arrays with square and hexagonal symmetry. As a main result we find that a fully polarized input beam is partly depolarized after transmission through a nanohole array. This loss of polarization coherence is found to be anisotropic; i.e., it depends on the polarization state of the input beam. The depolarization is ascribed to a combination of two factors: (i) the nonlocal response of the array as a result of surface-plasmon propagation and (ii) the non-plane-wave nature of a practical input beam.

The microscopic nature of donor-type SiSiO2 interface states

Abstract Donor-type interface states, generated by vacuum ultraviolet irradiation have been studied. They anneal at room temperature but only when in a neutral state. This anneal is accompanied by the release of atomic hydrogen. It is proposed that the states are formed by H loosely bonded to sites in the SiO 2 network at or near the interface. Anneal would take place by removal of H. Capturing a hole would strengthen the bond between H and the network site.

Influence of hydrogen silsesquioxane resist exposure temperature on ultrahigh resolution electron beam lithography

Performance of hydrogen silsesquioxane (HSQ) resist material with respect to the temperature during electron beam exposure was investigated. Electron beam exposure at elevated temperatures up to 90 °C shows sensitivity rise and slight contrast (γ) degradation compared to lower temperature cases. Ultrahigh resolution structures formed at elevated temperatures manifest better uniformity together with aspect ratio improvement and less linewidth broadening with overdose. Potential mechanisms for observed phenomena are proposed.

Helium Ion Lithography

Recent developments show that Scanning Helium Ion Beam Lithography (SHIBL) with a sub-nanometer beam diameter is a promising alternative fabrication technique for high-resolution nanostructures at high pattern densities. Key principles and critical conditions of the technique are explained. From existing data, the fundamental factors underlying the sensitivity gain by 1–2 orders of magnitude and the prospects for high resolution at high pattern densities are analysed. State-of-the-art performance of the technique is illustrated with experimental achievements in HSQ and PMMA resists. Exploratory SHIBL work on aluminum oxide resist is presented as a novel approach to overcome potential shot noise effects in pattern definition and to improve masking capabilities in subsequent pattern transfer.

Some considerations of effects-induced errors in resonant cantilevers with the laser deflection method

Micro/nano resonant cantilevers with a laser deflection readout have been very popular in sensing applications over the past years. Despite the popularity, however, most of the research has been devoted to increasing the sensitivity, and very little attention has been focused on effects-induced errors. Among these effects, the surface effects and the so-called readout back-action are the two most influential causes of errors. In this paper, we investigate (1) the influence of the surface effects such as water adsorption, gas adsorption, and generally surface contaminations, and (2) the effect of the laser deflection detection, including power and positions of the laser, on the resonance frequency of silicon cantilevers. Our results show that both the surface contaminations and the laser back-action effects can significantly change the resonant response of the cantilevers. We conclude that the effects have to be taken into account, particularly in the case of ultra high sensitivity cantilevers.