LASER PROCESSING FOR MICROELECTRONICS FABRICATION (WRITING, DEPOSITION, PHOTOCHEMISTRY, ORGANOMETALLICS, PYROLYSIS)

As integrated circuits become more complex, the need for maskless techniques of metallization, doping, and insulator formation become important. Maskless writing techniques allow the direct fabrication of microstructures on an integrated circuit by using a focused energy beam, e.g., a laser beam. These writing techniques can be used to repair integrated circuits thereby improving yield, make design changes and thus shorten turnaround time, and eventually customize generic integrated circuits. In this paper, we explore two aspects of maskless laser writing--silicon dioxide deposition and metal deposition.; The silicon dioxide deposition relies upon the laser induced thermal decomposition of an organosilicate layer. By translating the sample with respect to the focused laser beam, any pattern of silicon dioxide can be written onto the substrate. The laser formed silicon dioxide is comparable to conventially processed organosilicate layers as determined by infrared spectroscopy. Parametric studies and the process resolution are presented.; We next consider laser writing of metals. A summary of the various techniques for laser depositing metals is presented. In our experiments, the metal is liberated from an organometallic molecule. The results of photolytic deposition of cadmium, indium, and zinc and photo-thermal deposition of tungsten and molybdenum are presented. In general, these metals can be deposited with electrical conductivities approaching their respective bulk values. A theoretical model on deposition rates illustrating the importance of deposition from both the gas phase and the surface adsorbed layers is given. A practical problem in applying these techniques to IC repair is shown.; Finally, a survey of the current progress in large area laser processing is presented. Although large area laser processing is not a maskless technique, it generally can be considered resistless. The potential for laser processing in IC fabrication and the direction of future work is discussed.