Papers by Author: Z.Lj. Petrović

Abstract: A comprehensive simulation of etching profile evolution requires knowledge of the etching rates at all points of the profile surface during the etching process. Electrons do not contribute directly to the material removal, but they are the source, together with positive ions, of the profile charging that has many negative consequences on the final outcome of the process especially in the case of insulating material etching. The ability to simulate feature charging was added to the 3D level set profile evolution simulator described earlier. The ion and electron fluxes were computed along the feature using the Monte Carlo method. The surface potential profiles and electric field for the entire feature were generated by solving the Laplace equation using finite elements method. Calculations were performed in the case of a simplified model of Ar+/CF4 nonequilibrium plasma etching of SiO2.

Abstract: Neutral beam processing has evolved into one of the most promising methods for overcoming plasma process induced damage. Surface treatment by neutrals avoids problems with surface charging effects, frequently encountered when using common ion treatment, especially for low k-materials. In this paper, the influence of various parameters on the neutralization of ion beams in Ar-CF4 mixture based on a Particle in Cell with Monte Carlo collisions (PIC/MCC) simulation is studied. The efficiency of neutralization has been treated by considering both surface neutralization of ions and collisions of ions in the gas.

Abstract: Neutral beam etching is proposed as a candidate for reducing plasma-process-induced damage in nanoscale devices. In this paper, neutralization of ion beams due to both gas phase collisions and ion surface interactions based on a PIC (Particle in Cell) simulation of realistic Capacitively Coupled Plasma is presented. It was found that a satisfactory degree of neutralization might be achieved by a combined effect of charge transfer and surface collisions.

Abstract: Neutral beams were proposed for plasma etching in order to reduce damage due to charging. We analyzed the efficiency of neutralization in a system proposed recently where a beam of ions was neutralized in the gas phase and in a set of narrow tubes. We studied surface neutralization as well as collisions of ions in the gas. In the case of collisions of ions with aperture walls, efficiency of neutralization was assumed to be 100%. We also investigated the influence of various parameters such as aperture length, tube diameter and initial ion energy on the efficiency of neutralization using a Monte Carlo code for ion motion simulation. In our calculations we used a well-established set of cross sections for argon.

Abstract: Plasma reactor operating at low pressures (0.2-1 Torr) at 13.56 MHz has been developed with an idea to optimize the treatment of polymers, biological and textile materials. The reactor proved very effective in treatment of polymer surfaces and wool fabrics in order to improve wettability, efficiency of dyeing and printing as well as to reduce the felting shrinkage. It also gave good results in improving germination of seeds. The basic conditions that the reactor has to satisfy are: the energy of ions that hit the surface has to be low and the reactor should be efficient in production of active radicals. Two systems with different geometries were studied, both capacitively coupled plasma reactors operating at 13.56 MHz. Cylindrical geometry was selected in order to minimize the energy of ions reaching the surface. Modeling of the discharge was performed with an aim to verify the energy distribution function of ions. As a critical diagnostic test of the system, voltage and current probes were developed to check the operation mode of the discharge. Oxygen, air and argon were used with different results.

Abstract: The new concept of the combined treatment consisting of specific fibre surface tailoring and activation prior to biopolymer or enzyme post-application is introduced. Low-temperature plasma treatment is considered as very useful for superficial treatment of wool and hemp. Some interesting combinations of low-temperature plasma and enzymatic treatments are presented in this paper. These treatments result in an increase in wettability, dimensional stability, polymer adhesion and dyeability of both, wool and hemp fabrics.