Friedrich Lupp

Microwave-assisted laser dry etching of silicon

A combination of microwave excitation and a mask projection scheme is applied for laterally structured etching of silicon. The technology is based on polymerization of an inert overlayer, which protects the silicon surface from the etching gas. After ablating the polymer from the silicon surface with pulsed Excimer laser radiation the surface is exposed to an etching gas atmosphere. Different feed gases have been used, such as CF4, either nonactivated or activated in a microwave discharge. With these etching gases well-defined structures can be achieved with etching rates of 0.1 micrometers /min. Using a gas mixture of CF4 and CCl4 the etching rate can be increased to 1 micrometers /min. smooth etching profiles can be achieved with laser fluences < 0.6 J/cm2. Further, for the Si etching with MMA (methylmethacrylate) polymerization suitable processing variables for these competitive processes are obtained. The deposited polymer films and etched Si surfaces are characterized by ex-situ electron spectroscopies (XPS, AES) and the gas phase reactions are investigated with quadruple mass spectroscopy (QMS). The formation of ClF3 or ClF is discussed as a critical step within the microwave-assisted laser dry etching (MALDE) process. The presence of these species correlates with high Si etch rates.

Piloting Comprehensive Industrial Energy Efficiency Improvement in a European Rolling Stock Factory

A major share of the primary energy consumed globally has to be accounted to manufacturing, as well as related emissions have to. Improvement of energy efficiency in factories is therefore a key driver to support the achievement of the European 20/20/20 goals. Hence, industry has to rethink current approaches about design and management of manufacturing systems to take a significant step towards energy-efficient factories.

Comprehensive Improvement of Industrial Energy Efficiency: Pilot Case in a European Rolling Stock Factory

Energy and resource efficiency requires more suitable approaches to be consistently implemented in industry. Factories are more complex systems than residential or commercial buildings; in industrial domain, improvements for energy efficiency require measures that are difficult to be identified and that vary from building to manufacturing processes fields. This paper presents a comprehensive approach to systematically address industrial energy efficiency improvement. The approach has been developed and tested at a European rolling stock manufacturer. Insights from the pilot case presented confirm that this holistic view helps properly address energy efficiency in industrial domain.

Microstructuring of metal surfaces without burr by means of a combined oxidation-sublimation process in the focus of a laser beam

Hydrodynamical bearings for X-ray tubes made of molybdenum offer several advantages over ball bearings, one being the reduced noise, another the extended life time. A process has been developed to texture a molybdenum surface with a laser beam without generating blur. In order to avoid melt which may cause burr the material is evaporate via its oxides. A two step oxidation followed by the sublimation has been identified as governing process. The flat bottom of the groove is explained by the limited diffusion velocity of the oxygen and the reaction products. Incorporating a process control an accuracy of +/- 3 micrometers at groove depth of 20 micrometers was realized.

Patterning of Si(100) in Microwave-Assisted LDE (Laser Dry Etching)

Patterning of silicon is necessary in a number of microelectronic and micromechanic applications. Plasma processes, such as reactive ion etching, play an important role in VLSI and nanotechnology applications. The charged particles impinging onto the semiconductor surface may cause radiation damage, such as crystal defects of different dimensionality. In plasma etching processes resist patterning and a large number of processing steps are needed to perform etching. The laser-induced dry etching (LDE) process offers the possibilities of direct pattern transfer by mask projection, anisotropic etching with negligible damage, and etching with very high selectivity. Modifying the LDE-process by applying a microwave-excited gas results in more radicals and an increased etch rate. Some authors use Cl2 as the processing gas during the microwave-assisted laser dry etching (MALDE) with excimer laser radiation (248 nm) [1,2]. In this case the etch rate of Si(100) is below 1 A/pulse.