| Abstract [eng] |
Microfabrication of Erbium Oxide and III Group Nitrides by Photolithography and Etching The rare earth oxide Er2O3 is distinguished for its exceptional and diverse properties, which can benefit various fields of semiconductor technology. In particular, erbium oxide is characterized by a high dielectric constant (∼14), a wide bandgap (∼5.6 eV), high conduction band offset relative to silicon and high thermal and chemical resistivity. Erbium oxide grown on silicon substrates reacts poorly with Si and retains its properties unchanged even up to 900°C. All of these aforementioned properties are favorable for an application as a high-k gate dielectric in complementary-metal-oxide-semiconductor (CMOS) technology. Due to its stability erbium oxide can serve as a buffer layer for III group nitrides such as GaN epitaxially grown on silicon. Erbium oxide reduces the lattice mismatch between Si and GaN. However, due to the mismatch of thermal expansion coefficients, the cracks can be observed if thick GaN layers are grown. The cracks can be avoided in the formed films by patterning the substrate into separate areas. In such a patterned structure the stress is relieved by elastic relaxation of the film at the pattern edges. The unique properties and promising applications lead to the necessity to investigate the patterning of erbium oxide. The cheapest way to perform patterning is through the wet chemical etching. Till now, the comprehensive research in this area has not yet been presented. Therefore, in this paper we report on the wet etching mechanism of erbium oxide in sulfuric acid solution. The wet etching parameters were optimized to achieve well defined structures, and the surface morphology, as well as the etching mechanism were studied in detail. In the second part of the thesis the microfabrication of III group nitrides is also presented. Cheap plastic photolithography masks were chosen for the fabrication of LED structures. By performing several photolithography, etching and coating steps, a matrix of blue InGaN LED chips was successfully fabricated. These LEDs were characterized by electrical and optical methods. |
