Patterning of diamond like carbon films for sensor applications using silicon containing thermoplastic resist (SiPol) as a hard mask

Abstract

Patterning of diamond-like carbon (DLC) and DLC:metal nanocomposites is of interest for an increasing number of applications. We demonstrate a nanoimprint lithography process based on silicon containing thermoplastic resist combined with plasma etching for straightforward patterning of such films. A variety of different structures with few hundred nanometer feature size and moderate aspect ratios were successfully realized. The quality of produced patterns was directly investigated by the means of optical and scanning electron microscopy (SEM). Such structures were further assessed by employing them in the development of gratings for guided mode resonance (GMR) effect. Optical characterization of such leaky waveguide was compared with numerical simulations based on rigorous coupled wave analysis method with good agreement. The use of such structures as refractive index variation sensors is demonstrated with sensitivity up to 319 nm/RIU, achieving an improvement close to 450% in sensitivity compared to previously reported similar sensors. This pronounced GMR signal fully validates the employed DLC material, the technology to pattern it and the possibility to develop DLC based gratings as corrosion and wear resistant refractometry sensors that are able to operate under harsh conditions providing great value and versatility.

Diamond like carbon nanocomposites with embedded metallic nanoparticles

“…In most cases, it appears that reactive ion etching using a variety of feedstock gases (O 2 , CF 4 /O 2, SF 6 /O 2, SF 6 /O 2, etc) appears to be an effective tool in patterning of carbonaceous films. As an example, 1D and 2D microstructures for sensor applications produced by the inductively coupled plasma technique are presented in figure 9(a) [169]. Patterned a-C:H films: (i) 400 nm period 140 nm depth grating etched into DLC (ii) 380 nm period 300 nm depth grating etched into DLC (iii) hexagonal hole pattern (300 nm diameter, 380 nm depth) etched into DLC, (iv) hexagonal pillars pattern (300 nm diameter, 400 nm depth) etched into DLC and substrate) were etched using a SiPol (polymer-based Si-containing thermal resist) mask and using O 2 ions [169].…”

“…As an example, 1D and 2D microstructures for sensor applications produced by the inductively coupled plasma technique are presented in figure 9(a) [169]. Patterned a-C:H films: (i) 400 nm period 140 nm depth grating etched into DLC (ii) 380 nm period 300 nm depth grating etched into DLC (iii) hexagonal hole pattern (300 nm diameter, 380 nm depth) etched into DLC, (iv) hexagonal pillars pattern (300 nm diameter, 400 nm depth) etched into DLC and substrate) were etched using a SiPol (polymer-based Si-containing thermal resist) mask and using O 2 ions [169]. It is to be noted that the number of publications dedicated to the dry etching of DLC based metal nanocomposites is very limited.…”

“…It is to be noted that the number of publications dedicated to the dry etching of DLC based metal nanocomposites is very limited. Patterning of a-C:H matrix films with Al, Ti [161] and Ag filler [13,169] were reported. Such films were patterned employing plasma chemical etching and RIE in CF 4 /O 2 gas plasma [13,161], RIE in O 2 /Ar gas [161], ICP in O 2 /Ar [169] gas or combinations of mentioned methods.…”

Area-Selective, In-Situ Growth of Pd-Modified ZnO Nanowires on MEMS Hydrogen Sensors

“…At present, the patterning of nanomaterials on MEMS gas sensors still suffers from incompatibility between “bottom-up” synthesis processes and “top-down” microfabrication technology [ 11 , 12 ]. Some technologies, such as hard-mask deposition [ 13 , 14 , 15 ], screen printing [ 16 , 17 ], photolithography patterning [ 18 ], nanoimprinting [ 19 ], micropen direct writing [ 20 ], and hydrophobic/hydrophilic surface treatments coating [ 21 ] have been developed for the area-selective construction of nanomaterials. However, these methods still show limitations when exploited for micro-gas sensors.…”

Self-referenced refractive index sensor based on hybrid mode resonances in 2D metal-dielectric grating

“…GMR is an anomalous diffraction phenomenon in subwavelength gratings, which takes place due to the light diffracted from a grating structure coupling with the leaky waveguide mode [17]. The GMR effect occurs within a narrow linewidth and high efficiency [18] and the resonant wavelength is more sensitive to the change of the refractive index of the surrounding medium [19,20], which has been employed for optical sensors. The sensitivity of an optical sensor based on GMR is determined by the overlap intensity of the analytes and electromagnetic fields outside the structure.…”