Das reaktiv gesteuerte Ionenstrahlätzen von optischen Aluminiumoberflächen bietet einen vielversprechenden Prozessansatz, um Formfehlerkorrektur, Glättung periodischer Drehstrukturen und die Reduzierung von Rauheitsmerkmalen im Ortsfrequenzbereich der Mikrorauheit in einer Technologie zu kombinieren. Diese Arbeit konzentriert sich auf die experimentelle Analyse der niederenergetischen Ionenbestrahlung von einkorn-diamantgedrehten, technischen Aluminiumlegierungen RSA Al6061 und RSA Al905. Die Ionenstrahlbearbeitung unter Verwendung der Prozessgase Sauerstoff und Stickstoff ermöglicht eine direkte Oberflächenformfehlerkorrektur bis zu 1 µm Bearbeitungstiefe unter Beibehaltung der Ausgangsrauheit. Die sich aus dem vorangegangenen Formgebungsverfahren, dem Einkorn-diamantdrehen, ergebende Drehmarkenstruktur schränkt allerdings häufig die Anwendbarkeit dieser Spiegeloberflächen im kurzwelligen Spektralbereich ein. Daher wurde im Rahmen dieser Arbeit ein zweistufiger Prozessablauf entwickelt, um eine weitere Verbesserung der Oberflächenrauheit zu erreichen. Durch die Ionenstrahl-Planarisierungstechnik unter Verwendung einer Opferschicht werden die im hohen Ortsfrequenzbereich liegenden Drehmarken erfolgreich um insgesamt 82 % reduziert. Eine Kombination mit anschließender, direkter Ionenstrahlglättung zur nachfolgenden Verbesserung der Mikrorauigkeit wird vorgestellt. Um die Prozessführung in einem industrietauglichen Rahmen zu etablieren, wurden die experimentellen Untersuchungen mit einer 13,56 MHz betriebenen Hochfrequenz-Ionenquelle durchgeführt, konnten aber auch erfolgreich auf eine Breitstrahl-Ionenquelle vom Typ Kaufman übertragen werden.:Bibliographische Beschreibung iv
Danksagung vi
Table of Contents viii
1 Introduction 1
2 Surface engineering with energetic ions 8
2.1 Ion target interactions during ion beam erosion 8
2.2 Ion beam finishing methods 10
2.2.1 Ion beam figuring 11
2.2.2 Ion beam planarization 12
2.2.3 Ion beam smoothing 14
3 Experimental set-up and analytical methods 15
3.1 Experimental set-up 15
3.2 Kaufman-type broad beam ion source 18
3.3 Materials 19
3.3.1 Aluminium alloy materials 19
3.3.2 Photoresist materials as planarization layer 21
3.4 Surface topography error regimes 22
3.5 Analytical Methods 23
3.5.1 Analysis of surface roughness 23
3.5.1.1 White light interferometry (WLI) 23
3.5.1.2 Atomic force microscopy (AFM) 25
3.5.1.3 Power spectral density (PSD) analysis 27
3.5.2 Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) 29
3.5.3 X-ray photoelectron spectroscopy (XPS) 31
3.5.4 Time of flight- secondary ion mass spectrometry (ToF-SIMS) 32
3.5.5 Reflectometry 34
3.5.6 Photoresist composition 35
3.5.6.1 Attenuated total reflection infrared spectroscopy (ATR-IR) 35
3.5.6.2 Thermogravimetric analysis (TGA) 36
3.5.6.3 Differential scanning calorimetry (DSC) 38
3.5.6.4 Gas chromatography coupled mass spectrometry (GC-MS) 39
4 Surface engineering by reactive ion beam etching 41
4.1 Reactive ion beam etching with nitrogen 41
4.1.1 Dependence of the aluminium alloy composition 42
4.1.2 Ion beam etching of Al905 44
4.2 Local smoothing by reactive ion beam etching 50
4.2.1 Local surface error slope dependent sputter erosion 51
4.2.2 RIBE O2 direct smoothing 56
4.2.2.1 Oxygen finishing at 1.5 keV 56
4.2.2.2 Oxygen finishing at 0.6 keV 62
4.3 Conclusions 66
5 Technological aspects on photoresist preparation for ion beam planarization 69
5.1 Selection of a suitable photoresist 69
5.2 Photoresist application steps 71
5.2.1 DUV exposure of the photoresist layer 72
5.2.2 Postbake: the influence of the amount of organic solvent 73
5.2.3 Postbake: the influence of the baking temperature 74
5.3 Influence of process gas composition 77
5.3.1 Influence on roughness evolution during ion beam irradiation of the photoresist layer 78
5.3.2 Dependency of the process gas on the selectivity 79
5.4 Influence of the ion energy on the selectivity 80
5.5 Ion beam irradiation of the photoresist layer with nitrogen at different material removal depths 81
5.6 Conclusions 82
6 Ion beam planarization of optical aluminium surfaces RSA Al6061 and RSA Al905 84
6.1 Photoresist application on SPDT aluminium alloys 84
6.2 Ion beam planarization 85
6.2.1 Iterative nitrogen processing of RSA Al905 86
6.2.2 Iterative nitrogen processing of RSA Al6061 90
6.3 Ion beam direct smoothing 93
6.3.1 RIBE O2 smoothing of RSA Al905 93
6.3.2 RIBE O2 smoothing of RSA Al6061 97
6.4 Conclusions 101
7 Process transfer to a Kaufman-type broad beam ion source 103
7.1 RIBE machining investigations on RSA Al905 103
7.2 Ion beam planarization of RSA Al6061 106
7.3 Ion beam incidence angle dependent sputtering 107
7.4 Conclusions 113
8 Summary 115
9 Conclusions and Outlook 123
A List of abbreviations 127
B Selected properties of photoresist materials 129
References 131 / Reactively driven ion beam etching of optical aluminium surfaces provides a promising process route to combine figure error correction, smoothing of periodically turning structures and roughness features situated in the microroughness regime within one technology. This thesis focuses on experimental analysis of low-energy ion beam irradiation on single-point diamond turned technical aluminium alloys RSA Al6061 and RSA Al905. Reactively driven ion beam machining using oxygen and nitrogen process gases enables the direct surface error correction up to 1 µm machining depth while preserving the initial roughness. However, the periodic turning mark structures, which result from preliminary device shaping by single-point diamond turning, often limit the applicability of mirror surfaces in the short-periodic spectral range. Hence, during this work a two-step process route was developed to attain further improvement of the surface roughness. Within the ion beam planarization technique with the aid of a sacrificial layer, the turning marks situated in the high spatial frequency range are successfully reduced by overall 82 %. A combination with subsequently applied direct ion beam smoothing procedure to perform a subsequent improvement of the microroughness is presented. In order to establish the process control in an industrial framework, the experimental investigations were performed using a 13.56 MHz radio frequency ion source, but the developed process routes are also successfully transferred to a broad-beam Kaufman-type ion source.:Bibliographische Beschreibung iv
Danksagung vi
Table of Contents viii
1 Introduction 1
2 Surface engineering with energetic ions 8
2.1 Ion target interactions during ion beam erosion 8
2.2 Ion beam finishing methods 10
2.2.1 Ion beam figuring 11
2.2.2 Ion beam planarization 12
2.2.3 Ion beam smoothing 14
3 Experimental set-up and analytical methods 15
3.1 Experimental set-up 15
3.2 Kaufman-type broad beam ion source 18
3.3 Materials 19
3.3.1 Aluminium alloy materials 19
3.3.2 Photoresist materials as planarization layer 21
3.4 Surface topography error regimes 22
3.5 Analytical Methods 23
3.5.1 Analysis of surface roughness 23
3.5.1.1 White light interferometry (WLI) 23
3.5.1.2 Atomic force microscopy (AFM) 25
3.5.1.3 Power spectral density (PSD) analysis 27
3.5.2 Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) 29
3.5.3 X-ray photoelectron spectroscopy (XPS) 31
3.5.4 Time of flight- secondary ion mass spectrometry (ToF-SIMS) 32
3.5.5 Reflectometry 34
3.5.6 Photoresist composition 35
3.5.6.1 Attenuated total reflection infrared spectroscopy (ATR-IR) 35
3.5.6.2 Thermogravimetric analysis (TGA) 36
3.5.6.3 Differential scanning calorimetry (DSC) 38
3.5.6.4 Gas chromatography coupled mass spectrometry (GC-MS) 39
4 Surface engineering by reactive ion beam etching 41
4.1 Reactive ion beam etching with nitrogen 41
4.1.1 Dependence of the aluminium alloy composition 42
4.1.2 Ion beam etching of Al905 44
4.2 Local smoothing by reactive ion beam etching 50
4.2.1 Local surface error slope dependent sputter erosion 51
4.2.2 RIBE O2 direct smoothing 56
4.2.2.1 Oxygen finishing at 1.5 keV 56
4.2.2.2 Oxygen finishing at 0.6 keV 62
4.3 Conclusions 66
5 Technological aspects on photoresist preparation for ion beam planarization 69
5.1 Selection of a suitable photoresist 69
5.2 Photoresist application steps 71
5.2.1 DUV exposure of the photoresist layer 72
5.2.2 Postbake: the influence of the amount of organic solvent 73
5.2.3 Postbake: the influence of the baking temperature 74
5.3 Influence of process gas composition 77
5.3.1 Influence on roughness evolution during ion beam irradiation of the photoresist layer 78
5.3.2 Dependency of the process gas on the selectivity 79
5.4 Influence of the ion energy on the selectivity 80
5.5 Ion beam irradiation of the photoresist layer with nitrogen at different material removal depths 81
5.6 Conclusions 82
6 Ion beam planarization of optical aluminium surfaces RSA Al6061 and RSA Al905 84
6.1 Photoresist application on SPDT aluminium alloys 84
6.2 Ion beam planarization 85
6.2.1 Iterative nitrogen processing of RSA Al905 86
6.2.2 Iterative nitrogen processing of RSA Al6061 90
6.3 Ion beam direct smoothing 93
6.3.1 RIBE O2 smoothing of RSA Al905 93
6.3.2 RIBE O2 smoothing of RSA Al6061 97
6.4 Conclusions 101
7 Process transfer to a Kaufman-type broad beam ion source 103
7.1 RIBE machining investigations on RSA Al905 103
7.2 Ion beam planarization of RSA Al6061 106
7.3 Ion beam incidence angle dependent sputtering 107
7.4 Conclusions 113
8 Summary 115
9 Conclusions and Outlook 123
A List of abbreviations 127
B Selected properties of photoresist materials 129
References 131
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:72657 |
| Date | 30 October 2020 |
| Creators | Ulitschka, Melanie |
| Contributors | Arnold, T., Lasagni, A., Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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