Fabrication and Characterization of Silicon Micro-Funnels and Tapered Micro-Channels for Stochastic Sensing Applications

Abstract

We present a simplified, highly reproducible process to fabricate arrays of tapered silicon micro-funnels and micro-channels using a single lithographic step with a silicon oxide (SiO2) hard mask on at a wafer scale. Two approaches were used for the fabrication. The first one involves a single wet anisotropic etch step in concentrated potassium hydroxide (KOH) and the second one is a combined approach comprising Deep Reactive Ion Etch (DRIE) followed by wet anisotropic etching. The etching is performed through a 500 μm thick silicon wafer, and the resulting structures are characterized by sharp tapered ends with a sub-micron cross-sectional area at the tip. We discuss the influence of various parameters involved in the fabrication such as the size and thickness variability of the substrate, dry and wet anisotropic etching conditions, the etchant composition, temperature, diffusion and micro-masking effects, the quality of the hard mask in the uniformity and reproducibility of the structures, and the importance of a complete removal of debris and precipitates. The presence of apertures at the tip of the structures is corroborated through current voltage measurements and by the translocation of DNA through the apertures. The relevance of the results obtained in this report is discussed in terms of the potential use of these structures for stochastic sensing.

Micro/Nano Amorphization/Oxidation Of Silicon Induced By High Repetition Femtosecond Laser Pulses

“…As shown in Figure7.4, the irradiated zone was not etched; however, the non-irradiated area was dissolved during etching and finally, a pyramid-like structure was formed on silicon substrate. The etched (100) planes have a slope with an angle of 54.7°as expected[95].…”

Anisotropic diamond etching through thermochemical reaction between Ni and diamond in high-temperature water vapour

“…This indicates that the side walls of the diamond trenches are the {111} planes and they behave like etching stop planes. The anisotropy as mentioned above was extremely similar to that of Si etching by the KOH process 40 , 41 , which is frequently employed to fabricate Si trench structures for power devices. In reality, in terms of morphology, the diamond surface well-resembling the Si surface etched by the KOH process 40 , 41 was obtained through the proposed diamond etching process (Fig.…”

A Fluidic Interface with High Flow Uniformity for Reusable Large Area Resonant Biosensors

“…The global objective for the biosensor is at least to match the resolution of a standard SPR system that is placed somewhere near 0.1 nmol/L (or commonly described as 0.1 nM with M, named molar, representing the 1 mol/L concentration) [ 12 , 13 ]. The sensor ( Figure 1 ) separates the fluidic and the sensitive parts [ 14 ], allowing one to optimize them independently, and particularly ensuring good compatibility between bio-interface grafting and etching [ 15 , 16 ]. The sensitive part of the sensor has been described elsewhere [ 14 ], but we will present the main point of its design to better understand the key parameters of the fluidic interface.…”

“…Moreover, glass is susceptible to some form of corrosion in H 3 PO 4 acid, albeit at very slow rate at room temperature [ 23 ]. In the end, it appears that silicon fulfills all the material requirements and its micromachining has often been successfully used to fabricate complex bio-microdevices with microfluidic components [ 16 , 24 ]. Dry and wet etching techniques are by far the most common silicon bulk micromachining processes.…”