Zugl.: Chemnitz, Techn. Univ., Diss., 2010

Zugl.: Aachen, Techn. Hochsch., Diss., 2009

Techn. Universiẗat, Diss., 2004--Clausthal.

Techn. Hochsch., Diss--Aachen, 2008.

Zugl.: Aachen, Techn. Hochsch., Diss., 2008

University, Diss., 2002--Bremen.

Jet Electrochemical Machining (Jet-ECM) is a manufacturing technique that applies a free electrolyte jet to generate the desired shapes [1]. Since the principle of the technique is the same as other techniques of Electrochemical Machining where the material removal takes place based on the anodic dissolution of workpiece, the working distance, which is the distance between nozzle’s front surface and the workpiece surface, is one important parameter of the process. The working distance affects the current density and consequently the geometry removal. The control of the working distance can be done based on the data gathered before and during machining by surface measurement [2]. This measurement usually is done by using electrostatic probing to detect a limited amount of points of the initial workpiece surface. Since electrostatic probing is comparatively slow, laser triangulation represents an alternative technique to detect a larger amount of points before machining within significantly shorter time [3]. In addition to electrostatic probing and laser triangulation, the actual working distance can be measured during the machining process to realize constant working distance. This can be done by detecting electrical signals like the actual total current. This method can be combined with pre-machining measurement by laser triangulation in order to ensure the prevention of any collision between the nozzle and the workpiece. In this study, on-machine metrology techniques for measuring the working gap as well as current measurements will be compared. Besides, the advantages and disadvantages of these techniques will be systematized. In further studies, the possibility of combining the techniques will be investigated to enhance Jet-ECM with more accurate measurement techniques.

Due to unique advantages of Jet Electrochemical Machining (Jet‐ECM) such as the absence of mechanical and thermal effects, there is an increasing demand for the implementation of the technology in industrial sectors. However, meeting the stringent quality requirements of the current technological level is a challenge in Jet‐ECM especially for complicated microstructures. Hence, the implementation of an adequate metrology system is necessary to minimise deviations and to enhance the process towards zero‐defect‐manufacturing. The metrology system should be capable of measuring the workpiece before machining in order to enable the machine to adjust the process parameters and to reach the desired micro‐structure. Post‐machining measurements to compare the machined part with the desired shape should be possible as well. This will enhance the machine to make corrections on the workpiece before delivery to the next section in a process chain. However, in order to reach the desired microstructures, the characteristics of workpiece like material properties and previously machined structures on the size and shape of the machined microstructure should be taken into consideration. This is done through the implementation of results of the fingerprint study into the process control. In this study the effects of previously machined single grooves which intersect the secondly machined groove on the size, shape and surface roughness are investigated. The previously machined groove was generated by milling or Jet‐ECM. Since at the intersections the gap size changes and this lead to changes in current and current density, it is expected to observe changes in size and surface roughness. This investigation will show how grooves change at the intersections and whether the mentioned changes are significant. Besides, some suggestions will be provided in order to minimise the effects in Jet‐ECM of intersecting single grooves.

Es wird eine Alternative zum Ätzen von Siliciumnitrid (SiNx) auf Silicium-Wafern vorgestellt. Herkömmliche Verfahren zum Ätzen von SiNx auf Silicium-Wafern arbeiten mit Flusssäure oder Phosphorsäure. Zu diesen Chemikalien werden alternative organische Komplexbildner zum Ätzen von SiNx vorgestellt, welche im Gegensatz zu den herkömmlichen Substanzen weniger giftig und umweltschädlich sind. Bei den organischen Komplexbildnern handelt es sich um die Stoffgruppen der Hydroxycarbonsäuren und Aminosäuren. Für diese Substanzen wurden die ersten wichtigen Parameter für einen Einsatz in der Halbleiterindustrie untersucht. Dabei handelt es sich um Einflüsse durch die Herstellungsprozesse des SiNx selbst, des pH-Wertes, der chemischen Struktur des organischen Komplexbildners und die Konzentrations- und Temperaturabhängigkeit. Es werden für die Reaktion auch die ersten Reaktionsmechanismen postuliert.:1 Einleitung...................... 1 1.1 NachhaltigkeitinderHalbleiterindustrie................. 2 1.2 Nasschemische Ätzmethoden für Siliciumnitrid (SiNx).......... 5 1.3 ZieledieserForschungsarbeit........................ 9 2 Material und Methoden 11 2.1 Probenkörper ................................ 11 2.2 Ätzversuche ................................. 12 2.3 Charakterisierung.............................. 15 3 Ätzmittel für SiNx 25 3.1 Chemischer Aufbau von organischen Komplexbildnern für Siliciumnitrid.... 25 3.2 UntersuchungderMorphologie....................... 25 3.3 XPS-AnalysederOberfläche........................ 33 3.4 WirksameGruppen............................. 35 4 Methodenentwicklung zur Bestimmung von Ätzraten, Selektivität und Isotropie.... 37 4.1 Ätzrate.................................... 37 4.2 Selektivität................................. 39 4.3 Methoden zur Bestimmung der Schichtdickendifferenz .......... 43 4.4 Fehlerbetrachtung und Zusammenfassung der Methoden........ 46 4.5 Zusammenfassung der Messmethoden................... 51 5 Parameter mit Einfluss auf den Ätzprozess 53 5.1 Einfluss des Herstellungsprozesses..................... 53 5.2 Einfluss des pH-Wertes auf den SiNx-Abbau ................... 55 5.3 Einfluss von Wasser auf die Reaktion ................... 56 5.4 Einfluss der Struktur ............................ 57 5.5 Konzentrations- und Temperaturabhängigkeit der Ätzrate von Ätzmitteln 60 5.6 Untersuchung des kinetischen Verlaufs der Reaktion . . . . . . . . . . . 69 5.7 Untersuchung der Isotropie......................... 72 6 Postulierte Reaktionsmechanismen 77 6.1 Abbau des Stickstoffs aus der SiNx-Oberfläche . . . . . . . . . . . . . . 77 6.2 Abbau des Si aus der SiNx-Oberfläche................... 78 6.3 Milchsäure als Katalysator zum Abbau von elementarem Si . . . . . . . 80 6.4 NMR-Analyse................................ 82 7 Zusammenfassung und Ausblick 87 7.1 Zusammenfassung.............................. 87 7.2 Ausblick................................... 89 6.5 Ergebniszusammenfassung der postulierten Reaktionsmechanismen . . . 86

Jet Electrochemical Machining (Jet-ECM) is a manufacturing technique that applies a free electrolyte jet to generate the desired shapes [1]. Since the principle of the technique is the same as other techniques of Electrochemical Machining where the material removal takes place based on the anodic dissolution of workpiece, the working distance, which is the distance between nozzle’s front surface and the workpiece surface, is one important parameter of the process. The working distance affects the current density and consequently the geometry removal. The control of the working distance can be done based on the data gathered before and during machining by surface measurement [2]. This measurement usually is done by using electrostatic probing to detect a limited amount of points of the initial workpiece surface. Since electrostatic probing is comparatively slow, laser triangulation represents an alternative technique to detect a larger amount of points before machining within significantly shorter time [3]. In addition to electrostatic probing and laser triangulation, the actual working distance can be measured during the machining process to realize constant working distance. This can be done by detecting electrical signals like the actual total current. This method can be combined with pre-machining measurement by laser triangulation in order to ensure the prevention of any collision between the nozzle and the workpiece. In this study, on-machine metrology techniques for measuring the working gap as well as current measurements will be compared. Besides, the advantages and disadvantages of these techniques will be systematized. In further studies, the possibility of combining the techniques will be investigated to enhance Jet-ECM with more accurate measurement techniques.