Presently, there is a growing demand from the industry for microprocessing of materials. In particular, for applications in the field of microsystems technology it is necessary to produce structures with dimensions down to the micrometer scale especially in materials that could not be processed or processed well by conventional microelectronic technologies. We have been investigating the drilling of anodically bondable Pyrex glass by means of laser microprocessing using the excimer laser mask projection technique (248 or 193 nm wavelength, 10 ns pulse duration, 8 mJ pulse energy, 500 Hz repetition rate). We will show the dependence of the processing results on the laser parameters. The diameter of the holes ranges from 30 to 100 μm at the front side and from 1 to 50 μm at the rear side of the 500-μm-thick wafer. We observed the formation of cracks in the laser processed region. Accordingly, we found distinct relationships between the process parameters and the quality of the walls of the drilled holes. Especially the change from 248 to 193 nm wavelength led to a distinct decrease of crack formation but the wall at the rear side of the wafer shows still a break off of some material. As a solution the drilling of the wafer from both sides of the wafer allows us to produce crack free holes.
Laser micromachining has become a key enabling technology in the ever-continuing trend of miniaturization in microelectronics, micro-optics, and micromechanics. New applications have become commercially viable due to the emergence of innovative laser sources, such as diode pumped solid-state lasers (DPSSL), and the progress in processing technology. Examples of industrial applications are laser-drilled micro-injection nozzles for highly efficient automobile engines, or manufacturing of complex spinnerets for production of synthetic fibers. The unique advantages of laser-based techniques stem from their ability to produce high aspect ratio holes, while yielding low heat affected zones with exceptional surface quality, roundness and taper tolerances. Additionally, the ability to drill blind holes and slots in very hard materials such as diamond, silicon, sapphire, ceramics and steel is of great interest for many applications in microelectronics, semiconductor and automotive industry. This kind of high quality, high aspect ratio micromachining requires high peak power and short pulse durations.
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