Drilling of glass by excimer laser mask projection technique

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.