Pavol Nemec

Patterning of titanium oxide nanostructures by electron-beam lithography combined with plasma etching

Patterning of metal oxide nanostructures with precisely controlled geometries and spacings can play an important role in the improvement of sensors for gas detection. Titanium oxide thin films were deposited on oxidized silicon substrates by reactive magnetron sputtering at room temperature. Patterning of TiO2 nanostructures was conducted by electron beam lithography combined with plasma etching. It was found that for 120 nm-thick TiO2 nanostructure formation, HSQ e-beam resists and Cr films prove to be suitable mask materials. Experimental results showed that the size of TiO2 nanostructures depends mainly on the e-beam lithography process and they can be controlled by the design geometry and the exposure dose. TiO2 nanostructures with a minimal diameter of 70 nm and spacing of 200 nm were successfully fabricated by ICP etching in CF4/Ar plasma through negative e-beam resist HSQ.

The AZ 5214E Resist in EBDW Lithography and its Use as a RIE Etch–Mask in Etching Thin Ag Layers in N2 Plasma

Abstract In this article we describe the electron-beam direct-write (EBDW) lithography process for the AZ 5214E photoresist which is, besides its sensitivity to UV radiation, sensitive also to electrons. An adapted process flow is provided. At the same time we examine the resistance of this resist to RIE and its suitability as an etch-mask for etching thin Ag layers in N2 plasma. A comparison with several chosen resists (PMMA, ma-2405, ma-N 1402, SU-8 2000) is provided.

The effect of process parameters and annealing on the properties of Ti/Pt films for miniature temperature sensors

We present a Pt film temperature element of the size of 1.5×1.5 mm2 with the meander width of 20 μm. It was investigated the effect of Pt film thickness prepared on alumina ceramics and the post-deposition annealing process on structural and electrical properties. As-deposited Pt films are polycrystalline with strongly preferred orientation on the (111) plane and the grains size is about 20 nm. The peak strength of (111) increased after annealing for all investigated samples and also the grain sizes increased up to 67 nm. Annealed Pt films exhibit a lower resistivity in comparison with the as-deposited films.

Effects of HSQ e–beam Resist Processing on the Fabrication of ICP–RIE Etched TiO2 Nanostructures

Abstract Patterning of metal oxide nanostructures with different shapes and well-defined size may play an important role in the improvement of MEMS systems, sensors and optical devices. We investigated the effects of HSQ e-beam resist processing on the fabrication of sputtered TiO2 nanostructures. They were patterned using direct write e-beam lithography combined with ICP-RIE etching in CF4/Ar plasma. Experimental results confirmed that the HSQ resist with a thickness of about 600 nm is suitable as a masking material for optimal etching process and allows patterning of the dots array in TiO2 sputtered films with a thickness up 150 nm. TiO2 arrays with a minimal dots diameter of 180 nm and spacing of 1000 nm were successfully developed.

Optical properties of LEDs with patterned 1D photonic crystal

In this paper we focus on the application of the one-dimensional photonic crystal (1D PhC) structures on the top of Al0.295Ga0.705As/GaAs multi-quantum well light emitting diode (MQW LED). 1D PhC structures with periods of 600 nm, 700 nm, 800 nm, and 900 nm were fabricated by the E-Beam Direct Write (EBDW) Lithography. Effect of 1D PhC period on the light extraction enhancement was studied. 1D PhC LED radiation profiles were obtained from Near Surface Light Emission Images (NSLEI). Measurements showed the strongest light extraction enhancement using 800 nm period of PhC. Investigation of PhC LED radiation profiles showed strong light decoupling when light reaches PhC structure. Achieved LEE was from 22.6% for 600 nm PhC LED to 47.0% for 800 nm PhC LED. LED with PhC structure at its surface was simulated by FDTD simulation method under excitation of appropriate launch field.

Far Field Measurements of Phc Led Prepared by E–Beam Lithography

Abstract The paper deals with optical characterization of the Al0.295Ga0.705As/GaAs multi-quantum well light emitting diode (LED) structure with photonic crystal (2D PhC) patterned on the top of the structure using Electron Beam Direct Write Lithography (EBDWL). Light-current characteristics measured by integrating sphere shows increase of extracted light intensity as 21.1%. Additionally, extracted light intensity was studied by far-field measurements as a complementary method to light-current characteristics. The far-field measurements show increase of extracted light intensity as 31.2%. We suggest this method as more suitable for evaluation of extracted light intensity because it omits emission from edges of the LED and thus light is measured only from the area where PhC is patterned

Estimation of exposure parameters of chosen e-beam resists using variable shaped e-beam pattern generator

In this article we present results from lithography experiments on PMMA (positive tone), and HSQ Fox-12 and SU-8 (negative tone) resists carried out on the ZBA variable shaped e-beam pattern generators. In order to obtain the necessary information needed for the optimization of the exposure control Point Spread Function PSF, several lithography tests are mentioned. The carried out measurements and analysis of the results help us in obtaining important information about the resists and exposure processes and enable us to practically verify the suggested methods of parameters extraction for a reliable exposure model.