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Publisher Copyright: © 2021 American Chemical Society. All rights reserved. Copyright: Copyright 2021 Elsevier B.V., All rights reserved. Thermal atomic layer etching (ALEt) of amorphous Al2O3 was performed by alternate exposures of niobium pentafluoride (NbF5) and carbon tetrachloride (CCl4). The ALEt of Al2O3 is observed at temperatures from 380 to 460 °C. The etched thickness and the etch rate were determined using spectroscopic ellipsometry and verified by X-ray reflectivity. The maximum etch rate of about 1.4 Å/cycle and a linear increase of the removed film thickness with the number of etch cycles were obtained at a temperature of 460 °C. With the help of density functional theory calculations, an etch mechanism is proposed where NbF5 converts part of the Al2O3 surface into an AlF3 or aluminum oxyfluoride layer, which upon reacting with CCl4 is converted into volatile halide-containing byproducts, thus etching away the converted portion of the material. Consistent with this, a significant surface fluorine content of about 55 at. % was revealed when the elemental depth profile analysis of a thick NbF5-Treated Al2O3 layer was performed by X-ray photoelectron spectroscopy. The surface morphology of the reference, pre-, and postetch Al2O3 surfaces was analyzed using atomic force microscopy and bright-field transmission electron microscopy. Moreover, it is found that this process chemistry is able to etch Al2O3 selectively over silicon dioxide (SiO2) and silicon nitride (Si3N4).

Aktioparadigma on 80-luvulla kehitetty ohjelmointiparadigma, jossa ohjelman rakenne toteutetaan ohjelmantilaa varastoivien olioiden ja ohjelman suoritusta edistävien aktioiden avulla. Tämän paradigman päälle on lähdetty suunnittelemaan uutta aktiojärjestelmää, jonka keskeisenä ideana on esitellä uudenlainen aktioiden ympärille rakennettu rinnakkaisten ohjelmien suunnittelu ja toteutustapa, jossa siirretään mahdollisimman paljon rinnakkaisuuden vaatimista erikoisvaatimuksista laitteiston vastuulle huolehdittavaksi. Aktiojärjestelmällä suoritettavia ohjelmia tehdään uudella vielä suunnitteluvaiheessa olevalla aktio-ohjelmointikielellä, jota kutsutaan tässä diplomityössä lyhyesti aktiokieleksi. Aktiokielellä tehtävää aktio-ohjelmointia on suunniteltu käytettävän reaktiivisissa sulautetuissa järjestelmissä. Diplomityössä tehtiin alustavaa teoreettista selvitystyötä, kuinka aktiokielellä toteutettujen komponenttien välinen rajapintatoiminta kannattaisi toteuttaa. Komponentilla tarkoitetaan kokonaisuutta, jolla on muusta ohjelmasta erotettu sisäinen toteutus, jonka kanssa ulkomaailma kommunikoi käyttörajapinnan avulla. Aktiokieleen lisättiin komponenttien määrittelemiseksi kolme uutta rakennetta: käyttörajapinta, komponentti ja komponenttiolio. Näiden rakenteiden päälle suunniteltiin erilaisia tapoja toteuttaa komponenttien välinen rajapintatoiminta, jotka kuvattiin rajapintamalleina. Rajapintamallit suunniteltiin pääasiassa käyttämällä aktiokielen perusrakenteita, koska niitä käyttämällä minimoidaan muutokset aktiokieleen ja saadaan hyödynnettyä mahdollisimman paljon näiden rakenteiden jo olemassa olevia ominaisuuksia. Rajapintamalleja suunniteltiin yhteensä kuusi erilaista. Rajapintamalleissa esitettyjen ideoiden pohjalta aktiokieleen suunniteltiin rajapintakokonaisuus, jonka tarkoituksena on yhdistää rajapintamalleissa esitetyt toimivimmat ratkaisut esitykseksi aktiokielessä käytettäväksi standardirajapintarakenteeksi. Rajapintakokonaisuudessa päädyttiin tukemaan aktioita rajapintatoiminnan päärakenteena, koska niitä käyttämällä saadaan toteutettua helposti omaksuttava ja intuitiivinen rakenne käyttää. Aktiota käyttämällä rajapintatoimintaan saadaan selkeä työnjako, joka samalla tukee aktioiden roolia aktiokielen toiminnallisina rakenteina.

With a continuous pursuit of making semiconductor devices and integrated circuits (ICs) faster, better, and more energy efficient, the shrinking of device dimensions became imminent. Today we are approaching the ångström era, where the manufacturability of such devices is becoming challenging. As a result, atomic level processing (ALP) is now most desired. Atomic layer deposition (ALD) and atomic level etching are two such ALP methods that take full advantage of surface chemistry and allow growth and removal of atomistically thin layers of material on a substrate, respectively. Atomic level etching broadly describes the etching that maintains the ångström-level (i.e. below 1 nm) etched-thickness control and uses sequential gas-surface reactions that may be self-limiting. Atomic level etching can be either plasma based (plasma atomic layer etching - PALE), or thermal based (thermal atomic layer etching - ALEt, gas-phase pulsed etching - GPPE). PALE has existed at least for three decades. Although thermal atomic level etching is relatively new, it has evolved rapidly over the last seven years. In this thesis work, new thermal atomic level etching processes based on NbF5 , HF, CCl4 , SOCl2 , O2 , and O3/O2 reactants were developed. The materials that were removed selectively over SiO2 and Si3N4 are Al2O3, TiN, and HfO2 . Two types of etching processes were investigated, the first one uses sequential exposures of two or more reactants (ALEt), and the second uses pulsing of a single reactant (GPPE) to etch the target. The processes explored here show that the novel etch chemistries are capable of removing the material in the ångström regime isotropically from 3D structures. Thermochemical analyses of possible reactions based on the atomic-scale surface-gas models were carried out using first-principles calculations in density functional theory (DFT) as well as molecular dynamics (MD) simulations. In addition, potential etch reactions were also evaluated using conventional thermodynamic calculations. Finally, the post-etched surfaces were characterized using various surface sensitive techniques such as spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS), X-ray reflectivity/diffraction (XRR/XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), and weighing balance. With a continuous pursuit of making semiconductor devices and integrated circuits (ICs) faster, better, and more energy efficient, the shrinking of device dimensions became imminent. Today we are approaching the ångström era, where the manufacturability of such devices is becoming challenging. As a result, atomic level processing (ALP) is now most desired. Atomic layer deposition (ALD) and atomic level etching are two such ALP methods that take full advantage of surface chemistry and allow growth and removal of atomistically thin layers of material on a substrate, respectively. Atomic level etching broadly describes the etching that maintains the ångström-level (i.e. below 1 nm) etched-thickness control and uses sequential gas-surface reactions that may be self-limiting. Atomic level etching can be either plasma based (plasma atomic layer etching - PALE), or thermal based (thermal atomic layer etching - ALEt, gas-phase pulsed etching - GPPE). PALE has existed at least for three decades. Although thermal atomic level etching is relatively new, it has evolved rapidly over the last seven years. In this thesis work, new thermal atomic level etching processes based on NbF5 , HF, CCl4 , SOCl2 , O2 , and O3/O2 reactants were developed. The materials that were removed selectively over SiO2 and Si3N4 are Al2O3, TiN, and HfO2 . Two types of etching processes were investigated, the first one uses sequential exposures of two or more reactants (ALEt), and the second uses pulsing of a single reactant (GPPE) to etch the target. The processes explored here show that the novel etch chemistries are capable of removing the material in the ångström regime isotropically from 3D structures. Thermochemical analyses of possible reactions based on the atomic-scale surface-gas models were carried out using first-principles calculations in density functional theory (DFT) as well as molecular dynamics (MD) simulations. In addition, potential etch reactions were also evaluated using conventional thermodynamic calculations. Finally, the post-etched surfaces were characterized using various surface sensitive techniques such as spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS), X-ray reflectivity/diffraction (XRR/XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), and weighing balance.